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PICList Thread
'[EE]: WiFi 802.11b wireless networking links page'
2002\05\25@043201 by Russell McMahon

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Extremely good list of [EE]: WiFi 802.11b  wireless networking links.
Colour scheme interesting but content excellent.

       http://spacehopper.org/

Also numerous links to other material.
Very diverse - ranges from bizarre to very interesting.

   Satellite images from space
   3D mapping software
   Deep Cycle batteries
   Herbal
   Thai recipes
       much more .............

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'[EE]: WIFI <-- was Re: [PIC]:how do you think abou'
2002\12\27@011051 by Russell McMahon
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> .....I do however
> follow all the tech links people post on the list....I have quite an
archive
> going of stuff collected off the web that I hope to get around to sticking
> on a server on the Sydney wireless network when time permits. Just in case
> someone is interested in what it is, http://www.sydneywireless.com it's a
community
> based 802.11b based WAN spanning Sydney, some may be familiar with
> guerilla.net in the US....very similar....what better use of free
bandwidth
> then sharing knowledge?

I have an access point and two USB WIFI modules sitting here waiting a
"quiet" moment ... :-(
The Brisbane mesh I knew of - didn't realise Sydney had an equivalent.

What's the cheapest way to get an access point going? I had heard of a Linux
based AP but I believe they took an existing commercial AP and Linux-ised
it. Something using any old PC and a WIFI card and Linux would be nice.


       Russell McMahon

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2002\12\27@022938 by Jonathan Johnson

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I have an old P166 lying around I was going to use with Linux , I've heard
of heaps of these in use for just this purpose along with a wireless NIC and
a second NIC (100base) for my side of the gateway with maybe an extra one
for a DMZ for the server to keep it all nice n tight whilst I use the main
box as a gateway/firewall. the link below has truckloads of other links to
all sorts of this stuff
http://www.qsl.net/n9zia/wireless/page11.html

If you have the AP already then you can be up and running straight away but
you really should set up some sort of security to protect yourself from the
wireless wilds.


> {Original Message removed}

2002\12\27@035306 by Peter L. Peres

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On Fri, 27 Dec 2002, Russell McMahon wrote:

*>What's the cheapest way to get an access point going? I had heard of a Linux
*>based AP but I believe they took an existing commercial AP and Linux-ised
*>it. Something using any old PC and a WIFI card and Linux would be nice.

I haven't done it but it exists, I read about it on the net on one of the
wireless networking sites. Or was it a computer mag site.

Peter

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'[OT]: US Feds see WIFI as a terrorist risk'
2003\02\16@225627 by Russell McMahon
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Regulation threatened if manufacturers and users don't implement better WIFI
security.

       http://www.wired.com/news/wireless/0,1382,56742,00.html

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'[OT]: International WiFi hot spots?'
2003\03\27@131939 by Harold Hallikainen
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    Since we have an international audience here, I thought this might be a good place to ask...
    My aunt leads tours from the US to New Zealand and Australia. She'd like to set up a notebook computer so she can just walk into a wireless hot spot anywhere in the world and have access to the net (and her email, etc.). What's generally available for travelers like her? Are there free services that are widespread? Paid services that she could activate on a daily or monthly basis? Would she just set the wireless card to DHCP and DHCP would take care of the rest of it?

THANKS!

Harold




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2003\03\27@133658 by Herbert Graf

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>      Since we have an international audience here, I thought this
> might be a good place to ask...
>      My aunt leads tours from the US to New Zealand and
> Australia. She'd like to set up a notebook computer so she can
> just walk into a wireless hot spot anywhere in the world and have
> access to the net (and her email, etc.). What's generally
> available for travelers like her? Are there free services that
> are widespread? Paid services that she could activate on a daily
> or monthly basis? Would she just set the wireless card to DHCP
> and DHCP would take care of the rest of it?

       I don't know of a universal database for this sort of thing but I can
answer the second part. DHCP will be almost enough for MOST hotspots, you
would have to set the SSID. Some of the pay services may use encryption
which means you'd also have to enable encryption and enter the encryption
key. TTYL

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2003\03\27@134113 by Robert Ussery

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----- Original Message -----
From: "Herbert Graf" <mailinglistspamspam_OUTFARCITE.NET>

|         I don't know of a universal database for this sort of thing but I
can
| answer the second part. DHCP will be almost enough for MOST hotspots, you
| would have to set the SSID. Some of the pay services may use encryption
| which means you'd also have to enable encryption and enter the encryption
| key. TTYL

I assume the "war-driving" databases don't cover WiFi? They only contain
wireless network nodes, right? If not, they'd be a great source, since
they're available for almost everywhere. I certainly don't advocate
war-driving, but as long as the databases are there, why not use them
legally? (Again, assuming they include WiFi nodes)

- Robert

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2003\03\27@135118 by Herbert Graf

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> |         I don't know of a universal database for this sort of
> thing but I
> can
> | answer the second part. DHCP will be almost enough for MOST
> hotspots, you
> | would have to set the SSID. Some of the pay services may use encryption
> | which means you'd also have to enable encryption and enter the
> encryption
> | key. TTYL
>
> I assume the "war-driving" databases don't cover WiFi? They only contain
> wireless network nodes, right? If not, they'd be a great source, since
> they're available for almost everywhere. I certainly don't advocate
> war-driving, but as long as the databases are there, why not use them
> legally? (Again, assuming they include WiFi nodes)

       They do cover WiFi (in fact that's all most cover) however use of a network
without permission is very likely illegal, therefore I would NOT recommend
using these databases. Some do cross reference to publicly available
hotspots, however most are simply "open" access point databases. I'm not
sure how much trouble one would get in for using an access point without
permission, but I'm sure it's not good. TTYL

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'[OT]: International WiFi hot spots?'
2003\04\04@120125 by Patrik Husfloen
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www.wi-fizone.org/zoneLocator.asp?TID=7

found that url in a swedish tech-paper today.

/Patrik

Harold Hallikainen wrote:
{Quote hidden}

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2003\04\04@130059 by Harold Hallikainen

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THANKS! I note, however, that New Zealand is not listed...

Harold
---------- Patrik Husfloen <spamBeGonepathu440spamBeGonespamSTUDENT.LIU.SE> writes:


http://www.wi-fizone.org/zoneLocator.asp?TID=7

found that url in a swedish tech-paper today.

/Patrik

Harold Hallikainen wrote:
{Quote hidden}

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'[OT]: External WIFI antenna'
2003\12\11@203433 by rad0
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Do any of you know how to hook up a Bufalo outdoor antenna to
a WAP?

My question is, do you need two antennas or is everything in the Bufalo?


Thanks

A link to a step by step would be nice, thanks.

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2003\12\12@153916 by Nate Duehr

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rad0 wrote:

> Do any of you know how to hook up a Bufalo outdoor antenna to
> a WAP?

With good quality cable.  At 2.4 GHz, if you try to use standard RF
cable (like RG-8 or similar) the loss is very high and you'll end up
with very little RF actually reaching the antenna.  Typically at
microwave frequencies, something like LDF or hardline is used with
N-connectors.

> My question is, do you need two antennas or is everything in the Bufalo?

Don't know what a Buffalo is, but most outdoor 2.4 GHz antennas are
single antennas and most access points have a way of defining which
antenna port is used if they have two for receive-diversity.  Access
points that actually transmit through both antennas are extremely rare
if you can even find them, so you need to wire to the correct one.  Most
manufacturers do not tell you which is which, so you'd be best served by
either searching online for someone who's done it already or opening up
the AP and looking for the transmitter to see which antenna connector
it's attached to.

> A link to a step by step would be nice, thanks.

Google.  This is definitely the wrong list to ask this of, and you
didn't even mention which AP you have.

Watch out for what I would call "RF Voodoo" from online sites.  Pringles
can antennas are stupid (virtually no gain, and only directional, not
gain antennas), and most of the hobbiest 2.4 GHz 802.11b sites show
people using real crap for feedline, etc.  Find a ham operator who does
very high frequency (not VHF per-se... but REALLY high stuff) or
microwave guy in your local area and ask around for some spare hardline
or LDF or similar cable (this stuff can get very expensive) and get some
help making low-loss VERY short jumpers from whatever connector your AP
has on it to the hardline and you'll get GREAT performance.  Build it
with junk co-ax and it will seem to work well but you'll never know how
well it can really work.

Also - a note of caution - DO THE MATH and make sure you're within the
legal ERP limits for Part 15 802.11b devices.  You are on a shared band
with others and there are hundreds (if not thousands) of people running
illegal power levels out of their 802.11b outdoor antennas using 1W
amplifiers into directional high-gain antennas.  They don't bother to do
the math and they're generally naieve about the actual spectrum issues.
 Don't be one of those.

Nate, nateEraseMEspam.....natetech.com

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2003\12\12@155756 by Harold Hallikainen

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Also have a look at www.hallikainen.com/FccRules/2002/15/203/
regarding the legality of using an antenna other than that supplied by the
WAP manufacturer.

Harold



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2003\12\12@161038 by rad0

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Alright, the WAP is a linksys BEFW11S4 wireless router, it has two
antennas on the back.

I thought one was transmit and the other recieve.
Is this not true?

And the outdoor antenna I was going to use is a Buffalo Technology
outdoor directional antenna, WLE-HG-DYG.

Are you saying that I only need to run one, a single, coaxial cable
to this type of antenna?

And is there any likely chance that this will be over any power limits?
The antenna doesn't 'add' power does it?

I was going to buy it and hook it up.  I didn't know if I needed two
antennas or just one.

Thanks.

I'm aware that you need to use low impedance coaxial cable, I'm assuming
this is just high quality cable, or is there a brand or nomenclature for
this type
of cable?
I will put it on a pole so it is above a story and a half house.  25 feet
maybe.

{Original Message removed}

2003\12\12@164459 by Ishaan Dalal

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> Alright, the WAP is a linksys BEFW11S4 wireless router, it has two
> antennas on the back.
>
> I thought one was transmit and the other recieve.
> Is this not true?

No. BEFW11S4 has two antennae for diversity mode. If you are using an
external antenna, you will need to go into the router configuration page and
change the settings (Wireless..Advanced, IIRC; I no longer have that
router).

> Are you saying that I only need to run one, a single, coaxial cable
> to this type of antenna?

Yes.

> And is there any likely chance that this will be over any power limits?
> The antenna doesn't 'add' power does it?

No.

Cheers,
Ishaan

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2003\12\12@165742 by Nate Duehr

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Harold Hallikainen wrote:

> Also have a look at www.hallikainen.com/FccRules/2002/15/203/
> regarding the legality of using an antenna other than that supplied by the
> WAP manufacturer.

The "responsible party" in this document above is the owner of the AP.
The owner is allowed to change the antenna, but they then take on the
responsibility of maintaining the ERP limits for Part 15 devices -- if I
remember correctly.

Nate, RemoveMEnateTakeThisOuTspamspamnatetech.com

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2003\12\12@170407 by Dave Wheeler

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Hi,

Don't know what the FCC rules are or what power the AP transmits at but yes, the
antenna does add power in that your ERP can be greater than the applied power.
Done some calcs (using an online calculator)based on 25ft, 0.25W and 14dB gain
(as specified but very optimistic) and RG8. The results were:

Online Coax Cable Loss / Antenna Gain Calculator
================================================ Cable
Loss per 100 ft at Operating Frequency = 13.188 dB Cable Length = 25
Ft. Calculated Loss = 3.3 dB Power into Cable = .25 Watts Power out of
Cable = 0.1 Watts Gain of Antenna = 14 dBd ERP of Antenna System =
2.9 Watts Calculated 12/12/2003 at 9:59:25 PM
Which as you can see for a TX power of 0.25W gives you an ERP of 2.9W
which will almost certainly fall outside the FCC guidelines and cause
interference to secondary users (us poor Hams....)

Silly question but why do you want your AP to have a huge range in one
direction ?? The aerial quoted is directional (Probably a yagi in a plastic tube)
and will therefore only give gain in one direction and if well designed huge
losses on the nulls.

Cheers,

Dave (G0GMK)

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2003\12\12@172723 by Nate Duehr

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Ishaan Dalal wrote:

>>And is there any likely chance that this will be over any power limits?
>>The antenna doesn't 'add' power does it?
>
>
> No.

Wrong.  There are both power and ERP limits.  Effective Radiated Power
being a function of the antenna and how much power it focuses at the
horizon or direction you pointed it if it's a directional antenna.

If you use a gain antenna you could very well exceed the limits.
ESPECIALLY if you do like a lot of people and add a 1W power amplifier.

The Linksys has a 150mW transmitter, I believe.  So you'll have to do
the translation to dBm with your specific feedline loss and antenna gain
numbers to find out if you're over the limit.  You can't just say "no"
it won't go over them without doing the math.

What are the gain figures of this Buffalo thing in dB?

Nate, nateSTOPspamspamspam_OUTnatetech.com

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2003\12\12@210904 by michael brown

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From: "Ishaan Dalal"

> > The antenna doesn't 'add' power does it?
>
> No.

Hmm.... I respectfully believe this advice to be "effectively"
incorrect.  ;-)  ERP is what counts when transmitting and it makes
little difference whether you put 100 watts into a unity gain antenna
(isotropic point to be precise) or 10 watts into a 10dbi beam.  One nice
thing about using high gain antennas vs. more power is that they work in
reverse just as well.  IOW it doesn't do much good to add a power
booster to a WAP if it already can't hear the clients.

michael brown

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'[ot]: wifi cameras'
2004\01\12@181036 by rad0
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Can anyone explain or provide a link to an explanation
how this works?

I know the various wifi devices become items on the
wireless network.

Is a device like this 'home brewable'?

The camera, for instance, comes with an application that
evidently communicates with the camera and displays the
picture in a little window.

Thanks

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2004\01\12@182117 by Josh Koffman

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Well, I think you need to define home brewable. Also, it depends on how
small and integrated you want it to be. You could always put a USB
webcam on a laptop, stick an 802.11 card in it and run some software.
However, if you want it all in a tiny little package, if becomes much
harder. Coding for 802.11 isn't trivial, even on a processor designed
for IP communications like the IP2000 series from Ubicom.

Josh
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rad0 wrote:
> I know the various wifi devices become items on the
> wireless network.
>
> Is a device like this 'home brewable'?

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2004\01\12@192226 by M. Adam Davis

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I'd actually like more information about this, as I always considered
802.11 devices as simple packet devices - you give tham an ethernet
packet, and they deliver it to all the other 802.11 devices in range.  I
thought they took care of the physical layer completely.

Is there something more to 802.11 devices that I wouldn't have to deal
with on, say, an NE2000 ethernet card?

Thanks for the info!

-Adam

Josh Koffman wrote:

{Quote hidden}

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2004\01\12@192433 by Herbert Graf

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> Can anyone explain or provide a link to an explanation
> how this works?
>
> I know the various wifi devices become items on the
> wireless network.

       The devices I've seen basically have a web server embedded, to the network
the camera looks like any other Ethernet device, with a web server.

> Is a device like this 'home brewable'?

       Most definitely, easiest way is with an old computer an Linux. To keep it
similar in size to those on the market isn't trivial though.

> The camera, for instance, comes with an application that
> evidently communicates with the camera and displays the
> picture in a little window.

       Usually you open the connection with a web browser, the camera's server
uploads a Java applet that results in you seeing the video. Neat devices,
far to expensive at the moment for me, but prices will drop. TTYL

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2004\01\12@200701 by Liam O'Hagan

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You could perhaps implement such a device using something similar to the
Lantronix Xport that I'm in the process of buying...

http://www.lantronix.com

> {Original Message removed}

2004\01\12@220619 by Josh Koffman

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Hmm. Well, I remember a discussion a few years back, someone wanted to
use some 802.11 cards to run an intercom I believe. I think they
scrapped the idea when they realized that much of the work involved was
done in the software driver, not in the hardware, thus making embedded
work pretty hard. I'm guessing it's a lot harder than regular 802.3,
because you have to deal with added things like spread spectrum,
encryption, and while I haven't studied it in depth, I would guess there
is something running even below TCP that deals with radio packet
sequencing.

Just my thoughts though, use at your peril :)

Josh
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"M. Adam Davis" wrote:
> I'd actually like more information about this, as I always considered
> 802.11 devices as simple packet devices - you give tham an ethernet
> packet, and they deliver it to all the other 802.11 devices in range.  I
> thought they took care of the physical layer completely.
>
> Is there something more to 802.11 devices that I wouldn't have to deal
> with on, say, an NE2000 ethernet card?

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2004\01\12@225429 by M. Adam Davis

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The most recent discussion on this list about it (IIRC) was someone
wanting to record several channels of audio simultaneously, and the
reason 802.11 was scrapped was because you couldn't gurantee latency,
and just like ethernet if things get too congested packets start
dropping like crazy.

I was considering making a wifi phone last year with a compact flash
wifi card.  Not enough time...  One of these days I'll poke around the
available source code.

Unfortunately they are becoming more like winmodems - the processing of
packets, error detection/recovery, etc are moving away from the card.
An example of this is the Intel centrino.

-Adam

Josh Koffman wrote:

{Quote hidden}

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2004\01\13@015039 by Jonathan Johnson

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check the transfer rate of the device(actual throughput rate). Decide on
what level of resolution and compression your intending to use, this will
give you a size per frame, multiply this by the number of frames per second
you want to transmit, if you want real time video you will need 25fps for
PAL or 30 for NTSC, this will give you your required data rate. If the first
figure is less the second, go back to drawing board. if the first figure is
larger than the second, then decide on how you are going to implement your
compression algorithm (software or FPGA etc), you should about now have a
serial stream which you need to convert to TCP/IP packets (XPORT? I dont
know its throughput) then you will need an 802.11 type bridge for your
ethernet packets to be sent over the WLAN. at the other end you either need
an access point or bridge to get your ethernet packets back, next you will
need either a decompression engine and a composite video out or some
software to receive and decode the packets, ready for display.

I think that should be a basic rundown of what you need to do(excluding a
step here or there, nothing substantial...I think), but dont quote me as I
havent done one myself before.....and I'm tired n hungry :-)


Cheers


JJ

{Original Message removed}


'[OT]: weather station on a wifi network'
2004\04\24@160233 by rad0
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Does anyone make a weather station that you can access
via a wifi network?

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2004\04\24@204513 by M. Adam Davis

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Not yet... :-)

Unfortunately, Wi-Fi is pretty power hungry, so you'd have to have more
than the usual small solar panel/rechargable battery setup.

-Adam

rad0 wrote:

{Quote hidden}

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'[OT]: weather station on a wifi network. AVRs'
2004\04\26@174801 by Robert Rolf

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You could always get one of the 433Mhz or 915Mhz wireless stations and
connect the base station to a PC that does Wi-Fi. You can also get
better range with a 915Mhz system.

Now there's a project for that overpowered AVR Circuit Cellar contest.

Can someone familiar with AVR's point me at one that 'self programs'
like the PIC 16F8xx series, using the serial line?
e.g. 3 wire async interface not 6 wire like the AVR kit (or 5 that PIC ICSP)
uses.

Robert

"M. Adam Davis" wrote:
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2004\04\26@185121 by Richard.Prosser

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What about  the AtMega series - can program via bootloader -  is that what
you're after?
RP

project for that overpowered AVR Circuit Cellar contest.

Can someone familiar with AVR's point me at one that 'self programs'
like the PIC 16F8xx series, using the serial line?
e.g. 3 wire async interface not 6 wire like the AVR kit (or 5 that PIC
ICSP)
uses.

Robert

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2004\04\27@093704 by Mike Hord

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>Can someone familiar with AVR's point me at one that 'self programs'
>like the PIC 16F8xx series, using the serial line?
>e.g. 3 wire async interface not 6 wire like the AVR kit (or 5 that PIC
>ICSP)
>uses.
>
>Robert

Check out this:
http://www.atmel.com/dyn/products/param_table.asp?family_id=607&OrderBy=part_no&Direction=ASC

Note that the URL needs to be un-word-wrapped.  It's Atmel's
parametric product search for the AVR, and the second-to-last
column (towards the right side of the screen) is "Self-Program
Memory".

Handy little chart.

Mike H.

_________________________________________________________________
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'[OT:] Public WiFi access (was Microship project)'
2004\05\24@194915 by Howard Winter
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Lawrence,

Subject changed...

On Mon, 24 May 2004 17:11:17 -0500, .....llilespam_OUTspamSALTONUSA.COM wrote:

> Wifi services:
>
> So there is Tmobile, and some others, and sometimes they are free, and
> sometimes you have to add extra fees to use them unless you are already
> signed up, sometimes you can get to the one you are signed up with and
> sometimes not.  Beginning to sound babel-ish to me....

Yup!  Early days of a new "industry" so it hasn't settled down yet.  A supermarket near me has a coffee shop
with an "Internet Cafe" function - you can use their machines for about GB£3 an hour, and when it opened they
had WiFi access for nothing - but that honeymoon is over now and they charge the same for using your own
laptop on WiFi as for using their machines.

> And these fees  are in addition to your ISP?

They are completely unrelated to your ISP - you may not even have an ISP!  You are paying for a connection to
the Internet, rather like paying to use a public phone - it's not related to your home phone.

Cheers,

Howard Winter
St.Albans, England

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'[OT:] WIFI Waveguide antenna'
2004\08\02@005115 by Robert B.
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Has anybody had experiences with homebrew wifi antennas?  I built one this
evening similar to the "cantenna" described in various places on the web,
and it works OK, but not up to the level I was hoping for.

The cantenna is located in a room separate from the desktop PC which gets no
wifi signal at its manufacturer-supplied omni-antenna.  The laptop (built-in
wifi) picks up a strong signal where the cantenna is located, but the
desktop hooked to the cantenna in the same location picks up a very weak
signal (~-85db snr).  I used about 15 feet of standard coaxial cable as the
antenna line.. anybody know how to figure the theoretical signal loss
through it?  I'm not sure but I doubt coax was designed for 2ghz+
frequencies.  Does anybody know for certain?

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2004\08\02@005738 by David VanHorn

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At 11:50 PM 8/1/2004, Robert B. wrote:

>Has anybody had experiences with homebrew wifi antennas?  I built one this
>evening similar to the "cantenna" described in various places on the web,
>and it works OK, but not up to the level I was hoping for.
>
>The cantenna is located in a room separate from the desktop PC which gets no
>wifi signal at its manufacturer-supplied omni-antenna.  The laptop (built-in
>wifi) picks up a strong signal where the cantenna is located, but the
>desktop hooked to the cantenna in the same location picks up a very weak
>signal (~-85db snr).  I used about 15 feet of standard coaxial cable as the
>antenna line.. anybody know how to figure the theoretical signal loss
>through it?  I'm not sure but I doubt coax was designed for 2ghz+
>frequencies.  Does anybody know for certain?

Most of the antennas I've seen have used cans that are too small a diameter.
"Waveguide below cutoff".  Also, most small coax is pretty lossy at 2.5 GHz.
I've used RG-174 at 1.5 GHz for GPS, but not more than about 10', and with an amplified antenna.

Look at ham designs for antennas in the 2.3 GHz band and just scale it smaller a bit.

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2004\08\02@011555 by Robert B.

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Wouldn't too small a diameter create a wave guide *above* cutoff?  Or am I
missing something..  My can is about 3.5" wide, making the theoretical
cutoff right around 2500MHz.  Do you think a smaller can might work better?

{Original Message removed}

2004\08\02@013011 by Ian Stewart

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Check out this site
http://www.usbwifi.orcon.net.nz/

Ian
----- Original Message -----
From: "Robert B." <RemoveMEpiclistspamspamBeGoneNERDULATOR.NET>
To: <spamBeGonePICLIST@spam@spamspam_OUTMITVMA.MIT.EDU>
Sent: Monday, August 02, 2004 4:50 PM
Subject: [OT:] WIFI Waveguide antenna


> Has anybody had experiences with homebrew wifi antennas?  I built
one this
> evening similar to the "cantenna" described in various places on the
web,
> and it works OK, but not up to the level I was hoping for.
>
> The cantenna is located in a room separate from the desktop PC which
gets no
> wifi signal at its manufacturer-supplied omni-antenna.  The laptop
(built-in
> wifi) picks up a strong signal where the cantenna is located, but
the
> desktop hooked to the cantenna in the same location picks up a very
weak
> signal (~-85db snr).  I used about 15 feet of standard coaxial cable
as the
> antenna line.. anybody know how to figure the theoretical signal
loss
> through it?  I'm not sure but I doubt coax was designed for 2ghz+
> frequencies.  Does anybody know for certain?
>
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>

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2004\08\02@013014 by Robert Ussery

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>-----Original Message-----
>From: pic microcontroller discussion list [RemoveMEPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU]
>On Behalf Of Robert B.


>Has anybody had experiences with homebrew wifi antennas?  I built one this
>evening similar to the "cantenna" described in various places on the web,
>and it works OK, but not up to the level I was hoping for.
>
>The cantenna is located in a room separate from the desktop PC which gets
>no
>wifi signal at its manufacturer-supplied omni-antenna.  The laptop (built-
>in
>wifi) picks up a strong signal where the cantenna is located, but the
>desktop hooked to the cantenna in the same location picks up a very weak
>signal (~-85db snr).  I used about 15 feet of standard coaxial cable as the
>antenna line.. anybody know how to figure the theoretical signal loss
>through it?  I'm not sure but I doubt coax was designed for 2ghz+
>frequencies.  Does anybody know for certain?

I built one recently using a USB dongle and some Asian cookware, as
described on:

http://www.usbwifi.orcon.net.nz/

I used a free (after rebate) USB dongle from ecost.com, and a $10 18" wok
lid from "The Cupboard" (a local cookware shop - possibly a chain). I don't
have any hard performance numbers on it yet, but it can operate at much
lower SNR's than my $80 Proxim wireless card, and seems very directional.
Off the top of my head, I'd guestimate that I'm getting about 15-20db gain.
If I get around to it, I'll post a page on my website (I have pics, but no
page yet), and post it to the list.


TTYL!

- Robert

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2004\08\02@014503 by Russell McMahon

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> The cantenna is located in a room separate from the desktop PC which gets
no
> wifi signal at its manufacturer-supplied omni-antenna.  The laptop
(built-in
> wifi) picks up a strong signal where the cantenna is located, but the
> desktop hooked to the cantenna in the same location picks up a very weak
> signal (~-85db snr).  I used about 15 feet of standard coaxial cable as
the
> antenna line..

The coax will be killing you. Coax rated for 2.4 GHZ is horrendously dear.
If you weren't offended by the price wou paid for it, it's not the right
stuff :-). Try a VERY (inconventiently) SHORT length first to get things
sorted and then go from there.

Pringle can's, which are often recommended, are too small in diameter. If
your can is visibly larger dia than a Pringle can you are probably OK.
Actual diameter is not critical as long as it is large enough.

This may be useful
YMMV

       http://www.saunalahti.fi/elepal/antenna2.html

Site which claims to have a workable cantenna
(Be worried that they also mention Pringle's cans :-) )

       http://www.turnpoint.net/wireless/index.html

Commercial Cantenna for $US13.
Picture will give you ideas on what works

       http://www.cantenna.com/



       RM

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2004\08\02@014710 by Richard Prosser

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I can't remember the exact figures but RG174 has a loss of something like
10.5db/100ft at 400MHz and 40dB/100ft at 2GHz. This works out to about
44db/100ft at 2.4GHz So 15 ft will be about  6.6db, assuming matched
operation and good connectors.

Loss increases linearly in db by length and withn the square root of
frequency - roughly although diaelectric losses catch up and increase
linearly above some point dependent on material. Screening losses also go
up linearly with frequency and depend on screen design.

Hence the RG174 loss at 2.4GHz is higher than the value calculated from the
400MHz value.

In a poorly matched condition you could get any result - but it will be
worse.

I think.

RP







At 11:50 PM 8/1/2004, Robert B. wrote:

>Has anybody had experiences with homebrew wifi antennas?  I built one this
>evening similar to the "cantenna" described in various places on the web,
>and it works OK, but not up to the level I was hoping for.
>
>The cantenna is located in a room separate from the desktop PC which gets
no
>wifi signal at its manufacturer-supplied omni-antenna.  The laptop
(built-in
>wifi) picks up a strong signal where the cantenna is located, but the
>desktop hooked to the cantenna in the same location picks up a very weak
>signal (~-85db snr).  I used about 15 feet of standard coaxial cable as
the
>antenna line.. anybody know how to figure the theoretical signal loss
>through it?  I'm not sure but I doubt coax was designed for 2ghz+
>frequencies.  Does anybody know for certain?

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2004\08\02@015123 by David VanHorn

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At 12:15 AM 8/2/2004, Robert B. wrote:

>Wouldn't too small a diameter create a wave guide *above* cutoff?  Or am I
>missing something..  My can is about 3.5" wide, making the theoretical
>cutoff right around 2500MHz.  Do you think a smaller can might work better?

Yes, late night.. :)

You might benefit from pushing it out a bit more.


You can also mount your wi-fi thingy in the focus of a dish. Even those cheap primestar dishes will work, though their focus can be a bit non-obvuous at first.

That way you suffer no feedline losses at all, and AFAIK aren't technically in violation of part 15, as you haven't mechanically altered the antenna.

You can use powered repeaters to extend USB a fair bit, or use "USB-Anywhere" boxes to remote it.

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2004\08\02@015746 by Robert Ussery

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Here's the promised page:
http://users.frii.com/lmalpais/wokwifi/wifi.html

enjoy! Lots of good antenna pics. I still have to test the antenna, but
preliminary results with NetStumbler indicate significant gain improvements
over the raw dongle, and even over high-quality wireless cards.

TTYL!

- Robert

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2004\08\02@015747 by Marc Nicholas

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Or use Ethernet<-->Wifi bridges :-)

I recently purchased a commercial waveguide ("Super Cantenna") and can
vouch that bigger than a Pringles can is definitely where it's at. I'd
also say if you can fab something like this yourself (or appropriate
something), then save your money :-)


 -marc

On Mon, 2 Aug 2004, David VanHorn wrote:

{Quote hidden}

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2004\08\02@082451 by John J. McDonough

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----- Original Message -----
From: "Richard Prosser" <.....Richard.ProsserRemoveMEspamPOWERWARE.COM>
Subject: Re: [OT:] WIFI Waveguide antenna


> In a poorly matched condition you could get any result - but it will be
> worse.

It seems unlikely that this antenna will be a good match, and the mismatched
result will always be worse, sometimes astonishingly so.  Its pretty easy
for a mismatch to multiply the loss by an order of magnitude or two.  I'm
assuming by "standard coaxial cable" the OP meant RG-59/U, which, while it
isn't as bad as 174, is still pretty awful.  Take awful and multiply it by
10 or 100 and you quickly get to horrible.

--McD

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2004\08\02@083326 by Howard Winter

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Robert,

On Mon, 2 Aug 2004 00:50:16 -0400, Robert B. wrote:

> I used about 15 feet of standard coaxial cable as the
> antenna line.. anybody know how to figure the theoretical signal loss
> through it?

Not unless you tell us what it is!  There's no such thing as "standard" coax - standard for what?  TV?
Satellite?  Ethernet?  Amateur radio?  You want something that has 50ohm impedance, which rules out TV and
Satellite (75 ohm).

Have a look here:  http://www.ocarc.ca/coax.htm  for a calculator to show cable loss.

These are for 15' of various types at 2.4GHz, assuming you have good 50 ohm matching:

RG 174  9.035dB (about 88% attenuation)
RG 58C  6.34dB  (about 77% attenuation)
RG 58   3.87dB  (about 65% attenuation)
RG213   2.173dB (about 40% attenuation)

Which means that whatever you put into one end of an RG174 cable, only an eighth of it would come out of the
other end, which is a Bad Thing!

Now RG213 is big and unwieldy, and isn't justified from these figures, so if I was doing this I'd go for RG58.

Cheers,


Howard Winter
St.Albans, England

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2004\08\02@093305 by David VanHorn

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At 07:34 AM 8/2/2004, Howard Winter wrote:

>Robert,
>
>On Mon, 2 Aug 2004 00:50:16 -0400, Robert B. wrote:
>
>> I used about 15 feet of standard coaxial cable as the
>> antenna line.. anybody know how to figure the theoretical signal loss
>> through it?
>
>Not unless you tell us what it is!  There's no such thing as "standard" coax - standard for what?  TV?
>Satellite?  Ethernet?  Amateur radio?  You want something that has 50ohm impedance, which rules out TV and
>Satellite (75 ohm).

Actually, 75 ohm cable is less lossy up high (in general) and might be a better choice.
Some antennas match better to 75 than to 50, and at the card end, a 1.5-1 VSWR isn't a big deal.  Far more important that the antenna be resonant.  Tough to know up here without specialized equipment.

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2004\08\02@102044 by John Ferrell

face picon face
> That way you suffer no feedline losses at all, and AFAIK aren't
technically in violation of part 15, as you haven't mechanically altered the
antenna.
>
I think it has more to do with effective radiated power (ERP). I doubt an
experimenter would be challenged on the subject but a commercial product
would.

It has been a long time ago but I did a lot of experimenting at 1296 mhz.

Some things I learned:
If the transmitter is located at the radiator there are NO feedline losses.
If the antenna is resonant, the RF will get to it.
If the antenna is inside, prototyping is cheap & easy.
 Kitchen grade aluminum and cardboard work well for even finished products.
Hold things together with hot melt glue, tape, staples.
Bigger usually works better than smaller.
The further you get from quarter or half wave radiators the tougher the
problem becomes.
Dr. John Kraus was the last guy to do anything really new with antennas.

Be aware of interferrenc from other 2.5G signals. I have an X10 TV link, a
microwave oven, a cordless phone and a WIFI connection at my house.

John Ferrell
http://DixieNC.US

{Original Message removed}

2004\08\02@104821 by Russell McMahon

face
flavicon
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> > That way you suffer no feedline losses at all, and AFAIK aren't
> technically in violation of part 15, as you haven't mechanically altered
the
> antenna.

> I think it has more to do with effective radiated power (ERP). I doubt an
> experimenter would be challenged on the subject but a commercial product
> would.

Definitely ERP in any enlightened administration.
FCC qualify as enlightened ;-)

ERP can be horrendously high for amateur playing. I have heard people talk
about putting amplifiers in front of WiFi cards already rated at 100 mW+
This plus a half decent dish will cause major havoc while not gaining vastly
more than is possible with care and legal gear.

A well designed larger but not huge (around 30") dish will give 18 dB plus
gain and legal limit ERP (figures don't rise to top of brain at moment)(+15
dBm?).
Add equal dish at other end and an OK receiver and short decent coax and
good elevation and you are looking at over 20 mile links. Some report WELL
over. Few people need or can manage what goes with a 20 mile plus link.

Good elevation near ends of link is vital for range due to Fresnel zones.
Falling ground until well clear is highly desirable. Those repeaters aren't
on hilltops by mistake.


       RM

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2004\08\02@111312 by Robert B.

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Sorry, I just pulled a scrap out of the basement.  I'm pretty sure it's RG58
though, and either way it looks like it seriously attenuates my signal :(

To get my desktop out of the dead spot takes at least 15' of some sort of
cable, and I haven't been able to locate anything that doesn't kill the
signal.  I guess it does technically *work* now (I'm typing this email with
the cantenna taped to the door-frame) so maybe I'll just mount it
permanently and suffer through the slow 4Mbs network connection.
{Original Message removed}

2004\08\02@111727 by Robert B.

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These are all good things to know!  I don't have any other 2.4ghz signals
besides the wifi and an occasional microwave.  The microwave was dropped at
one point, so spews out lots of extra radiation in that band when its
operated.  My neighbor's 2.4ghz phone system sometimes mysteriously craps
out whenever I cook a hotdog ;-)

Now that I mention it, I wonder if his phone could be an interference
source.  Too bad my scope only works up to 100MHz :(


{Original Message removed}

2004\08\02@112142 by Robert B.

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Maybe I'll have to give this idea a shot.  By moving the signal receiver to
the dish the signal probably gets a whole lot better at distances from the
host PC.  The USB cable could be up to 16ft, just enough to get the antenna
into the signal area.  And I suppose there wouldn't be anywhere near the
loss problems with a longish USB cable.  Too bad I wasted money on this darn
PCI adapter!


{Original Message removed}

2004\08\02@112350 by Robert B.

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face
I built mine out of an old tomatoe juice can just under 4" diameter and
about 10" tall, then installed the probe as per the web-calculators
available.  It sounds like I'm probably sniffing at the wrong hydrant, and
should try locating one of those USB dongles at the focal point of a dish,
then run the USB cable back to my PC.


{Original Message removed}

2004\08\02@112559 by Alan B. Pearce

face picon face
>The microwave was dropped at one point, so spews out lots
>of extra radiation in that band when its operated.  My
>neighbor's 2.4ghz phone system sometimes mysteriously craps
>out whenever I cook a hotdog ;-)

Sheesh mate. Replace it real quick. hate to think what you are doing to
yourself with this thing. !!!!!!!!

>Now that I mention it, I wonder if his phone could be an
>interference source.

And what is your network doing to his phone ???? :)))))

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2004\08\02@114047 by hael Rigby-Jones

picon face
>-----Original Message-----
>From: pic microcontroller discussion list
>[spamBeGonePICLIST@spam@spamMITVMA.MIT.EDU] On Behalf Of Robert B.
>Sent: 02 August 2004 16:22
>To: RemoveMEPICLISTEraseMEspamKILLspamMITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>Maybe I'll have to give this idea a shot.  By moving the
>signal receiver to the dish the signal probably gets a whole
>lot better at distances from the host PC.  The USB cable could
>be up to 16ft, just enough to get the antenna into the signal
>area.  And I suppose there wouldn't be anywhere near the loss
>problems with a longish USB cable.  Too bad I wasted money on
>this darn PCI adapter!

Definitely the way to go.  The USB adapters are also dirt cheap, I just
bought an 802.11G dongle (need USB2 to get full bandwidth) for just over £20
($36) in "rip-off Britain" so I suspect the 11mbit/s dongles are virtualy
pennies in the US.

Mike

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2004\08\02@114916 by Alan B. Pearce

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>Definitely the way to go.  The USB adapters are also dirt
>cheap, I just bought an 802.11G dongle (need USB2 to get
>full bandwidth) for just over £20 ($36) in "rip-off Britain"
>so I suspect the 11mbit/s dongles are virtualy
>pennies in the US.

Where did you get that Michael? I have had a look on ebay and they go for
close to twice that for the .11g ones, but about that for .11b. Reason I am
interested is that it seems like a nice way to add wifi to my Linux firewall
that I want to set up, which will have a spare USB plug on it.

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2004\08\02@114918 by David VanHorn

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>
>ERP can be horrendously high for amateur playing. I have heard people talk
>about putting amplifiers in front of WiFi cards already rated at 100 mW+
>This plus a half decent dish will cause major havoc while not gaining vastly
>more than is possible with care and legal gear.

I'm only licensed for 1500W up here.. :)

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2004\08\02@115124 by David VanHorn

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At 10:16 AM 8/2/2004, Robert B. wrote:

>These are all good things to know!  I don't have any other 2.4ghz signals
>besides the wifi and an occasional microwave.  The microwave was dropped at
>one point, so spews out lots of extra radiation in that band when its
>operated.  My neighbor's 2.4ghz phone system sometimes mysteriously craps
>out whenever I cook a hotdog ;-)

I would seriously think about getting that checked.

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2004\08\02@120158 by Robert B.

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I checked around it with a fluorescent tube, and it appears to be a highly
directional leak towards my neighbor's house.  I know its crude, but its the
best I could do.  So I just go in the other room (away from the leak)
whenever something has to nuke for any length of time.  It's really not a
very good microwave, so I probably should just replace it, but I really
didn't think it was all that dangerous.  It sounds like maybe I'm wrong...


{Original Message removed}

2004\08\02@120406 by hael Rigby-Jones

picon face
>-----Original Message-----
>From: pic microcontroller discussion list
>[RemoveMEPICLISTKILLspamspamTakeThisOuTMITVMA.MIT.EDU] On Behalf Of Alan B. Pearce
>Sent: 02 August 2004 16:50
>To: spamBeGonePICLISTspam@spam@MITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>>Definitely the way to go.  The USB adapters are also dirt
>cheap, I just
>>bought an 802.11G dongle (need USB2 to get full bandwidth) for just
>>over £20 ($36) in "rip-off Britain" so I suspect the 11mbit/s dongles
>>are virtualy pennies in the US.
>
>Where did you get that Michael? I have had a look on ebay and
>they go for close to twice that for the .11g ones, but about
>that for .11b. Reason I am interested is that it seems like a
>nice way to add wifi to my Linux firewall that I want to set
>up, which will have a spare USB plug on it.

http://www.ebuyer.co.uk (quickfind code 63002) is the actual device I
bought. However, I have just checked and the product I bought seems to have
gone up to £27.99.  Not unusual for Ebuyer however, they do seem to have a
very "flexible" pricing policy.  Worth keeping an eye on it though as I've
known prices to go down shortly after they've been increased.

There is an alternative device for £22.99 (quickfind code 60710) that is a
little bit larger and has an external antenna which may well be better if
you aren't intending on putting it in front of a dish.
Note that they are described as being of "Ebuyer" brand, but in relality
they simply sell whichever product they can get the cheapest, which may or
may not be in retail packaging.  The one I bought was made by Origo
http://www.origo2000.com/show-prds.php?ID_NUM=80

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2004\08\02@120614 by hael Rigby-Jones

picon face
>-----Original Message-----
>From: pic microcontroller discussion list
>[PICLISTspamspamMITVMA.MIT.EDU] On Behalf Of Robert B.
>Sent: 02 August 2004 17:01
>To: spam_OUTPICLISTspam_OUTspamspam_OUTMITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>I checked around it with a fluorescent tube, and it appears to
>be a highly directional leak towards my neighbor's house.  I
>know its crude, but its the best I could do.  So I just go in
>the other room (away from the leak) whenever something has to
>nuke for any length of time.  It's really not a very good
>microwave, so I probably should just replace it, but I really
>didn't think it was all that dangerous.  It sounds like maybe
>I'm wrong...

With the cost of a new microwave oven as low as they are, I don't think I'd
be taking the risk to be honest.  Your neighbour might not be very
understanding if he knew you were slowly cooking him as well :o)

Mike

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2004\08\02@121234 by David VanHorn

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>
>With the cost of a new microwave oven as low as they are, I don't think I'd
>be taking the risk to be honest.  Your neighbour might not be very
>understanding if he knew you were slowly cooking him as well :o)

TOSS IT.

If you're lighting up a tube, you're emitting WAY too much!

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\02@131732 by Robert B.

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face
The way I understand it, any escaped microwaves would only heat me up.  I
don't ever feel warmer when the microwave is running, therefore I am not
very concerned.  The oven's rating is 800W, 2450MHz.  Even if all that
radiation escaped in a concentrated beam, it would still be far below many
commercial microwave transmitters.  I've heard stories of tech's sitting
near the microwave transmitter beams to keep warm in the winter, so I'm
still having trouble believing a little microwave radiation leakage could
actually do any damage.

I'm certainly no expert, and if you have a source indicating that it is
actually dangerous I'd love to read it.  I'm sure there are some HAMs on
this list (apparently you, Dave?) who know all about microwave radiation and
might have a link or two so I could learn about it too.

So far in my research I've discovered that the FDA advocates less than
2mW/cm2 leakage for new ovens.  This is apparently to avoid interfering with
communications devices rather than protect the biological species using the
microwave.

At any rate, I probably shouldn't let my friend do this anymore:
http://nerdulator.net/misc/ian.JPG



{Original Message removed}

2004\08\02@133843 by David VanHorn

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At 12:17 PM 8/2/2004, Robert B. wrote:

>The way I understand it, any escaped microwaves would only heat me up.  I
>don't ever feel warmer when the microwave is running, therefore I am not
>very concerned.  The oven's rating is 800W, 2450MHz.  Even if all that
>radiation escaped in a concentrated beam, it would still be far below many
>commercial microwave transmitters.  I've heard stories of tech's sitting
>near the microwave transmitter beams to keep warm in the winter, so I'm
>still having trouble believing a little microwave radiation leakage could
>actually do any damage.

RF safety is not so easy.
You can develop cataracts in your eyes from this sort of thing, but not immediately.
DONT screw around with it.

I'm licenced for 1500W (which to me is silly and obscene at this frequency) but you wouldn't find me anywhere near the antenna when operating.  Even at 1W I would not want to be anywhere close to the antenna.

I'm not a hysterical reactionary, but I do believe in the inverse square law. :)

http://www.telecomlab.gr/2002/oct/rhodes/pap3rs/N%20108%20(p775%20-%20p780).pdf

The antennas on my car, are on the other side of a nice metal roof. Very little energy gets inside.  I don't use an HT much, and when I do, I keep the antenna away from my head.

>At any rate, I probably shouldn't let my friend do this anymore:
>http://nerdulator.net/misc/ian.JPG

Me, I would cut off the AC cord, take it out to the trash, and bash in the door with a brick.

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2004\08\02@140834 by Denny Esterline

picon face
> At any rate, I probably shouldn't let my friend do this anymore:
> http://nerdulator.net/misc/ian.JPG
>

Depends on how much you like him... :o)

-Denny

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2004\08\02@141250 by Lawrence Lile

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Don't bash in the door - get inside the thing and take the magnet out of
it.  Believe me it is worth it, takes a screwdriver and about 2 minutes.
There are two SERIOUS magnets inside an 800 watt microwave - the kind of
magnets that will pinch a blood blister on your fingers if you get a
pinky between two of them.  That is what I use for refrigerator magnets
- you can put a framed picture of Mom on the fridge and it won't fall
off! Heat up a screwdriver and stick it on this magnet and when it cools
off it is a magnetic screwdriver.
Also, the microwave oven is totally and completely disabled if you take
out the magnet  <grin>
-- Lawrence Lile, P.E.
Electrical and Electronic Solutions
Project Solutions Companies
http://www.projsolco.com


> {Original Message removed}

2004\08\02@141705 by David VanHorn

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At 01:09 PM 8/2/2004, Lawrence Lile wrote:

>Don't bash in the door - get inside the thing and take the magnet out of
>it.  Believe me it is worth it, takes a screwdriver and about 2 minutes.
>There are two SERIOUS magnets inside an 800 watt microwave - the kind of
>magnets that will pinch a blood blister on your fingers if you get a
>pinky between two of them.

What shape?

> That is what I use for refrigerator magnets
>- you can put a framed picture of Mom on the fridge and it won't fall
>off! Heat up a screwdriver and stick it on this magnet and when it cools
>off it is a magnetic screwdriver.

Yes, I suppose so. Still for the average guy, the potentially charged filter cap is a significant hazard. The disassembly could be a little bit interesting.


>Also, the microwave oven is totally and completely disabled if you take
>out the magnet  <grin>

Kinda lets the mag out of the magnetron.. :)


I do have an article reprint on making an AM TV transmitter by adding a modulator to a microwave oven. Theoretically workable, but I don't know anyone who has done it.

Even my buddy WA1MKE (known around here as "microwave dave") hasn't taken that plunge yet.

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2004\08\02@143337 by M. Adam Davis

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David VanHorn wrote:

>At 01:09 PM 8/2/2004, Lawrence Lile wrote:
>
>
>>magnets that will pinch a blood blister on your fingers if you get a
>>pinky between two of them.
>>
>>
>
>What shape?
>
>
Probably a puffy ovoid shape, but it depends on how much skin gets
between the magnets... :-)

-Adam

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2004\08\02@151113 by Lawrence Lile

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> What shape?
>
Doughnut shaped, about 8cm diameter and 3cm thick



> Yes, I suppose so. Still for the average guy, the potentially charged
> filter cap is a significant hazard. The disassembly could be a little
bit
> interesting.

Oh Yeah, make sure you find that cap and stick a screwdriver across it.
It is supposed to have a discharge resistor across it, but sometimes
they fail...

>
>
> >Also, the microwave oven is totally and completely disabled if you
take
> >out the magnet  <grin>
>
> Kinda lets the mag out of the magnetron.. :)
>
Yeah, sorta like a airplane without the air, or a rocket ship without
the rocket, or a pistol without the ... (hey this is a family list
here..)

>
>
> Even my buddy WA1MKE (known around here as "microwave dave") hasn't
taken
> that plunge yet.
>
I thought Microwave Dave was doing 10-20 after that last mod.  
--Lawrence Lile

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2004\08\02@155228 by Roland

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face
At 02:06 PM 02/08/2004 -0500, you wrote:
>> What shape?
>>
>
>Doughnut shaped, about 8cm diameter and 3cm thick
>
>
>
>> Yes, I suppose so. Still for the average guy, the potentially charged
>> filter cap is a significant hazard. The disassembly could be a little
>bit
>> interesting.

Years ago I put a magneron in the bandsaw to get a good look inside.
interesting. I'm sure you could get KW's out of it by applying the correct
DC to it. (+cooling)

Anyway, I really don't like the idea of handling powerful DC magnets.
Another one of those 'unknown long term effects' like RF and the rest.

Back to the 'countdowm..' topic, a magnetic field is necessary for life on
earth, and so we are susceptable to magnetic fields in general. Something
the scientists don't adress is that an artificial field is needed for deep
space travel. Also then, scanning planets for magnetic fields is a first
test for possible life.

Regards
Roland Jollivet

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2004\08\02@165120 by Lawrence Lile

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> Back to the 'countdowm..' topic, a magnetic field is necessary for
life on
> earth, and so we are susceptable to magnetic fields in general.
Something
> the scientists don't adress is that an artificial field is needed for
deep
> space travel. Also then, scanning planets for magnetic fields is a
first
> test for possible life.
>

I'd have to agree that a magnetic field around the planet is necessary
for a good radiation shield.  I am not so sure why a field is necessary
to sustain an astronaut, provided he is inside a suitable can of some
kind, or an alien slime mold, provided he is built like a cockroach and
doesn't mind a few gamma rays for breakfast.  
>
> Anyway, I really don't like the idea of handling powerful DC magnets.
> Another one of those 'unknown long term effects' like RF and the rest.
>

So far those "unknown long term effects" have produced nil as far as
repeatable, statistically signifigant effects from magnetic or electric
fields commonly encountered.  
On the other hand, the public has been panicking about this for years,
since the 80's when one study found a slight statistical correlation
between proximity to substations and some kind of cancer.  Nevermind the
study was on a small population, positive results were never replicated,
and was repeated many times over with negative results, the public is
still frothing at the mouth about it.  It resurfaced when somebody sued
because they had a cell phone and happened also to get brain cancer, a
coincidence, and the public has grabbed onto that anecdote and used it
as proof, jury and judge.  
Scientists can pack rats into cages with all kinds of magnetic fields
for years and find no ill effects vs controls, and these studies have
been done over and over again because the public keeps demanding it.
They "know" that emf causes disease and don't believe any other result.

> Regards
> Roland Jollivet

On the other hand...  maybe you are right!  <GRIN> <moves away from
monitor, buys handsfree ten foot pole for his cell phone>
--Lawrence

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2004\08\02@165706 by John J. McDonough

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----- Original Message -----
From: "Lawrence Lile" <@spam@llileSTOPspamspam@spam@PROJSOLCO.COM>
Subject: Re: [OT:] Microwave ovens was WIFI Waveguide antenna


> Oh Yeah, make sure you find that cap and stick a screwdriver across it.
> It is supposed to have a discharge resistor across it, but sometimes
> they fail...

And don't use your favorite screwdriver!

--McD

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2004\08\02@180012 by Robert Rolf

picon face
What always amuses me about the 'panicked public' is that
the body's intrinsic operating voltages (across nerve
membranes) are on the order of 50kV/meter. ORDERS of magnitude
above what you would get from typical external EM fields.
Muscles also produce 100's of millivolts, again over tiny
scales, so you have low kV/meter all the time (remember that
your heart is beating all the time and you do have to breath).

External EM fields are down in the noise compared to what
body cells are exposed to on a continuous basis.
And the body electrolytes are highly conductive, highly
attenuating higher RF frequencies with depth.

And if the 'radiation' is non-ionizing, the worst that can
happen is that you get warmed up a bit, which is not a problem
since your blood carries away the heat. The only body part
that is not protected by this cooling process is the lens and
cornea of the eye. Cook those (42C+) and you DO have a problem,
but nothing fatal.

I work in Neuroscience, and have reviewed the literature because
of the RF excited implanted stimulators we use for rehab. FES.

There are also TNS (Transcranial Neural Stimulators) which create
kilo Tesla fields to directly stimulate deep brain regions.
None of the 10's of thousands of patients exposed to these
fields has ever been reported as having come down with brain
cancer or related diseases, and given the sample space and EM
strength, this SHOULD have happened if there were a causal
relationship.

And lets not forget the statistics of TENS OF MILLIONS of
cellular phone users, and their NOT having brain cancers
at anything above random rates.

Robert
The sky is falling... NOT!

Lawrence Lile wrote:

{Quote hidden}

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2004\08\02@180632 by David VanHorn

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At 02:06 PM 8/2/2004, Lawrence Lile wrote:

>> What shape?
>>
>
>Doughnut shaped, about 8cm diameter and 3cm thick

Hmm. Might be fun to scrap out some old units.
Not rare earth, NIB, right?

>Oh Yeah, make sure you find that cap and stick a screwdriver across it.
>It is supposed to have a discharge resistor across it, but sometimes
>they fail...

I always assume they have failed.

>>
>>
>> Even my buddy WA1MKE (known around here as "microwave dave") hasn't
>taken
>> that plunge yet.
>>
>
>I thought Microwave Dave was doing 10-20 after that last mod.

?? Dave's an instructor at the academy, at Ball State Univ.

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2004\08\02@181221 by Bob Blick

face picon face
> What always amuses me about the 'panicked public' is that
> the body's intrinsic operating voltages (across nerve
> membranes) are on the order of 50kV/meter. ORDERS of magnitude
> above what you would get from typical external EM fields.
> Muscles also produce 100's of millivolts, again over tiny
> scales, so you have low kV/meter all the time (remember that
> your heart is beating all the time and you do have to breath).

That argument is totally unconvincing to me. I could counter that by
saying a television set has 25 kV, yet it is able to receive very small RF
(and IR) signals.

There are plenty of studies that say there's no link between smoking and
cancer - it depends who funds the study.

Let the public panic - maybe they'll get some exercise :)

Cheerful regards,

Bob

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2004\08\02@200140 by William Chops Westfield

face picon face
On Aug 2, 2004, at 10:17 AM, Robert B. wrote:

> The way I understand it, any escaped microwaves would only heat me up.

Ah, you haven't read either Brunner's "The Sheep Look up", or Varley's
"Press Enter", then.  Nice horrific scenes involving microwaves that'll
change the way you look at ovens, regardless of their level of
technical accuracy...

Shudder
BillW

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2004\08\02@211403 by Russell McMahon

face
flavicon
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> What always amuses me about the 'panicked public' is that
> the body's intrinsic operating voltages (across nerve
> membranes) are on the order of 50kV/meter. ORDERS of magnitude
> above what you would get from typical external EM fields.
> Muscles also produce 100's of millivolts, again over tiny
> scales, so you have low kV/meter all the time (remember that
> your heart is beating all the time and you do have to breath).

etc
All good stuff.
But prudent avoidance is still prudent IMHO.
Don't have to destroy one's life over such things.
But much of post disaster assessment is working out how what couldn't
possibly have happened happened, and how it could have been foreseen, and
how not to let it happen again. Even though it will.

So far the US is two Shuttles down, can see with blinding clarity in
hindsight what was going wrong, but walked into both disasters blithely.


       Russell McMahon

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2004\08\02@211403 by Russell McMahon

face
flavicon
face
What part of "cooked food" don't you understand ? :-)

> The way I understand it, any escaped microwaves would only heat me up.  I
> don't ever feel warmer when the microwave is running, therefore I am not
> very concerned.

They'd wlecome you with open arms as a worker at any asbestos factory :-)

The debate re the effects of non-ionising radiation is a century or so long.
Correlation of cancer levels with various related occupations can be shown.
Standards vary between countries BUT your microwave will happily exceed them
all :-). Quit apart from the possible obscure phsyilogical effects which may
or may not exist, a good dose of microwaves can cause cataracts - localised
burning. I suspect you would like to avoid this happening in your eyes and
brain at least. Brain hasn't got too much water in the outer cladding but
there are lots of nice resonant molecules just under that hard shell. Eyes
are nicely full of water from surface in. The 2400 GHz band is an ISM band
AND is used for microwave heating precisely because water has an absorbtion
line there.

> The oven's rating is 800W, 2450MHz.  Even if all that
> radiation escaped in a concentrated beam, it would still be far below many
> commercial microwave transmitters.

Below many, yes. Above many in watts/m^2, yes. How concentrated the beam is
from the nice slot radiator you may have made by dropping it is unknown. A
slot radiator is an entirely useful form of antenna. How good your one is is
of course unknown. Don't make its day by finding out.

> I've heard stories of tech's sitting
> near the microwave transmitter beams to keep warm in the winter,

Many "Darwin Award" stories are untrue.
Many true Darwin Award stories are unbelievably unbelievable.
It's hard to imagine anyone doing the really really stupid things that
people really do.

> so I'm
> still having trouble believing a little microwave radiation leakage could
> actually do any damage.

YMWPV.

> I'm certainly no expert, and if you have a source indicating that it is
> actually dangerous I'd love to read it.  I'm sure there are some HAMs on
> this list (apparently you, Dave?) who know all about microwave radiation
and
> might have a link or two so I could learn about it too.

The web is utterly full of RF radiation hazrad warnings. The closest one to
you will probably be printed on a lable on your microwave. Every new
microwave I came with came with a warning that said - "Don't Do IT !!" or
similar.

What part of cooked food don't you understand ? :-)

> So far in my research I've discovered that the FDA advocates less than
> 2mW/cm2 leakage for new ovens.  This is apparently to avoid interfering
with
> communications devices rather than protect the biological species using
the
> microwave.

One of the international levels for human exposure is 10 mW/cm^2.
How good is your slot radiator?

Take 100 cc (3 ounces) of water in  aplastic bag.
Hang bag on a string across known leakage area.
Run over for several minutes.
Test water temperature.
Regardless of result, throw over away.



       Russell McMahon

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2004\08\02@214556 by Robert Ussery

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face
>-----Original Message-----
>From: pic microcontroller discussion list [EraseMEPICLISTSTOPspamspamRemoveMEMITVMA.MIT.EDU]
>On Behalf Of Russell McMahon

>YMWPV.

Wow! That's an obscure one... I googled for it, and only came up with 10
results, none of which had a definition of it. I checked all the usual lingo
dictionaries, and none of them had it...

What's it mean? More importantly, perhaps, where'd you pick it up?

I can get "You may want p-something v-something", but I can't figure it out.

TTYL!

- Robert

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2004\08\02@215352 by Robert B.

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I read it as "your mileage will probably vary", but on second thought its
probably "your mother would probably vomit".


----- Original Message -----
From: "Robert Ussery" <TakeThisOuTuavscienceRemoveMEspam@spam@FRII.COM>
To: <EraseMEPICLISTRemoveMEspamMITVMA.MIT.EDU>
Sent: Monday, August 02, 2004 9:42 PM
Subject: Re: [OT:] Microwave ovens was WIFI Waveguide antenna


> >{Original Message removed}

2004\08\02@215808 by Robert Rolf

picon face
Russell McMahon wrote:

> What part of "cooked food" don't you understand ? :-)

It's only 'cooked' if you denature the proteins. That requires
temperatures over 42C.

>>The way I understand it, any escaped microwaves would only heat me up.  I
>>don't ever feel warmer when the microwave is running, therefore I am not
>>very concerned.

> They'd wlecome you with open arms as a worker at any asbestos factory :-)

And kilowatts of RF energy is used in diathermy treatments in hospital
physiotheraphy wards. (deep heating of injured tissues increase blood
flow and healing).

> all :-). Quit apart from the possible obscure phsyilogical effects which may
> or may not exist, a good dose of microwaves can cause cataracts - localised
> burning.

Yep. And since the cornea's and lens have no nerves, you'd never
know you were cooking until you blinked and your eyelids felt the
surface heat.

{Quote hidden}

Don't forget to have a 'control' bag of water to account
for room temperature heating. i.e. same bag, same start temp,
same place, same time, but WITHOUT powering the over.

http://www.gallawa.com/microtech/output.html

Over the years manufacturers have used several different methods to rate
the output wattage of microwave ovens. First, there was the  traditional
 method. Then, in 1989-90 came the  JIS  (Japanese Industrial
Standard). Using the JIS method, ovens rated at 700 watts using the
traditional  method became 750-watt ovens. In 1990-91 the industry
changed to the international  IEC-705  standard. This pushed the wattage
ratings even higher. For example, models rated at 700  traditional
watts were instantly turned into 800-watt ovens using the IEC-705 formula.

   1.   Procedure:   Pour exactly 1000 mL (1 Liter) of cool tap water
into the container. Using the thermometer, stir the water, then measure
and record the temperature. For accurate results the water should be
about 60 degrees F (20 degrees C).
   2. Place the container on the center of the oven cooking shelf (do
not leave the thermometer in the container and remove any metal racks),
and heat the water (at full power) for 63 seconds. Use the second hand
of a watch, not the oven timer. [OLD OLD ovens]
   3. After the heating time is completed, immediately remove the
container, stir the water, re-measure and record the temperature of the
heated water.
   4. Subtract the starting water temperature (step 2) from the ending
water temperature (step 3) to obtain the temperature rise.
   5.
      To determine the output power in watts, multiply the total
temperature rise by a factor of:
          38.75 , if you're using a Fahrenheit thermometer;
          70 , if you're using a centigrade thermometer.

{some other sites say multiply by 35 for delta in F.
Someone want to derive the equations from first principles?}

Robert

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2004\08\02@220223 by Robert Ussery

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>-----Original Message-----
>From: pic microcontroller discussion list [PICLISTspam_OUTspam@spam@MITVMA.MIT.EDU]
>On Behalf Of Robert B.


>I read it as "your mileage will probably vary", but on second thought its
>probably "your mother would probably vomit".

Gotcha... Given the original context, I'm sure you're right.

Your mother probably would vomit if she could see how you live, eating only
microwave cooked food, tanning with a broken microwave oven, etc.*
<grin>

Darn it, Russell, you're talking over my head, again.

But then again, YMWPV.

- Robert






* for those on this list with no sense of humor, this is sarcasm. Just
CYA-ing (or would that be CMA-ing?)

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2004\08\02@222143 by Robert B.

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FWIW I'm planning on ditching the death-ray, just because theres no sense in
taking any easily avoidable risk.  But...  I'm still not convinced there's
much danger to be had in my particular unit.  I tried the water-bag test,
and it didn't feel any warmer than when the test started.  Waving one of
those tiny little fluorescent camping-lantern tubes around the edge it was
dropped on reveals a small area in which the tube is lit ever-so-dimly,
unobservable except in the dark, and even then you have to look closely.  No
heat is sensed (with my hand) around any portion of the microwave while its
running, and it still cooks food as fast as it ever did.  Moreover, I don't
ever run it empty, so the majority of the death-ray is absorbed by the food
I'm about to eat.

After a century or so of debate, I'm of the opinion that firm facts and
studies would have clearly demonstrated any long-term harmful effects of
non-ionizing radiation.  Aside from cooking your corneas (which happens
fairly quickly), I haven't seen anything more than a statistical blip in any
of the related medical studies.  Everybody "warns" against it, but nobody
has any significant evidence that it actually does long term harm.  IMHO its
a non-problem.  Sort of like people freaking out about a bit of
ionizing-radiation every now and then.

The warning labels all read like death-ray radiation warning labels should,
but thats certainly more for liability than anything else.  I hardly take
warning labels to be an objective source of scientific fact, though they
should of course (at the very least) be carefully considered before ignoring
them ;)

Moreover, all the "harmful effects" I've encountered in any study I've read
from non-ionizing radiation were more or less instantaneous.  IE if your
corneas are gonna be cooked you'll find out real quick, as opposed to
cumulatively over weeks, months or years.

But yes, I'll cave to safety and get rid of it.  But when I dispose of it,
its gonna be a fantastic explosion for sure.  None of this just smashing it
with a brick stuff.

{Original Message removed}

2004\08\02@224046 by Russell McMahon

face
flavicon
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> >YMWPV.

YMMV       = Your mileage may vary
YMWPV    = Your mileage will probably vary :-)



       RM        = Russell McMahon

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2004\08\03@015418 by Roland

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>I work in Neuroscience, and have reviewed the literature because
>of the RF excited implanted stimulators we use for rehab. FES.
>
>There are also TNS (Transcranial Neural Stimulators) which create
>kilo Tesla fields to directly stimulate deep brain regions.
>None of the 10's of thousands of patients exposed to these
>fields has ever been reported as having come down with brain
>cancer or related diseases, and given the sample space and EM
>strength, this SHOULD have happened if there were a causal
>relationship.

mmm, science again. This is tantamount to using a cattle probe to stimulate
your PC. Also falls in with the concept of frontal lobotomies as a 'cure'.

The human body is fantastically resilient to external influence, because of
it's self-healing properties, but it is also very sensitive. You won't
catch me near a MRI machine, let alone a doctor.
OK, doctors are useful, but it's mostly professional butchery.

Regards
Roland Jollivet

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'[OT:] WIFI Waveguide antenna'
2004\08\03@033738 by Alan B. Pearce

face picon face
Thanks for the pointer to ebuyer, Michael. Will have to investigate them
when I'm closer to needing one.

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\03@034152 by Alan B. Pearce

face picon face
>Heat up a screwdriver and stick it on this magnet
>and when it cools off it is a magnetic screwdriver.

You don't need to heat it, just wipe it across the pole faces a couple of
times.

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'[OT:] Microwave oven leakage (was: Re: [OT:] WIFI '
2004\08\03@041809 by Nate Duehr

face
flavicon
face
Robert B. wrote:

> I checked around it with a fluorescent tube, and it appears to be a highly
> directional leak towards my neighbor's house.  I know its crude, but its the
> best I could do.  So I just go in the other room (away from the leak)
> whenever something has to nuke for any length of time.  It's really not a
> very good microwave, so I probably should just replace it, but I really
> didn't think it was all that dangerous.  It sounds like maybe I'm wrong...

Well the inverse-square rule may be (literally) saving your skin.  Or at
least your eyes.  (Microwave energy is known to cause the formation of
cataracts.)

If it's cooking hotdogs and it's leaking out, it's also cooking you if
you're within a few meters of the oven when it's operating.

Perhaps it's time to get a newer oven with no leaks and to have a play
with the old one:

http://www.everist.org/special/mw_oven/

Disclaimer: Not responsible for you blowing yourself up if you try any
of this crazy stuff!  ;-)

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\03@043508 by Nate Duehr

face
flavicon
face
Robert Rolf wrote:
>    3. After the heating time is completed, immediately remove the
> container, stir the water, re-measure and record the temperature of the
> heated water.

In 63 seconds this should not happen, but be forewarned that in older
ovens without carousels, water in a container sitting very still can
become superheated in a microwave oven.  Upon disruption by some object
(thermometer in this case) the superheated (above boiling point but not
boiling) water can and will explode out of the container as it all
instantaneously boils over, flashing to steam and covering the
unsuspecting "scientist" with boiling water.

Carousels and ovens that naturally vibrate quite a bit are, of course,
less prone to this type of accident.  Ovens that leave the food very
still in a single location that heat a container of liquid very evenly
are more likely to do this.

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2004\08\03@060020 by Russell McMahon

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> water in a container sitting very still can
> become superheated in a microwave oven.  Upon disruption by some object
> (thermometer in this case) the superheated (above boiling point but not
> boiling) water can and will explode out of the container as it all
> instantaneously boils over, flashing to steam and covering the
> unsuspecting "scientist" with boiling water.

This is even more liable to occur if you boil the water, leave it in the
microwave oven to cool somewhat and then boil  again. The first heating
removes much of the dissolved air which otherwise acts as nucleation points
for localised boiling. Water and steam may both exist at 'boiling point" -
typically 100 C. Steam takes more energy BUT you can add energy to the water
without a unit mass having enough energy to convert to steam.

If none changes then all will stay the same (obviously enough) - for a
while. If a little changes it may disturb the  surrounding water enough to
cause it to take up any extra energy available and make the phase change.
While undisturbed the heated water starts to transition between solid state
and gaseous state but has no localised points at which this may occur
preferentially. Finally something disturbs it enough to trigger a chain
reaction. This provocation can be essentially spontaneous or may be caused
by stirring or carrying. I believe that a major part of the liquid can
decide to leave rapidly.

The fact that the microwave energy is applied much more evenly to the vessel
also "helps". With normal bottom up thermal heating the water is circulated
by convection currents and this disturbance helps to destroy the low
disturbance environment needed.

I have actually tried to induce this effect several times without success -
was spur of the moment effort and not consistently approached.

HOWEVER - I saw it happen to someone else about 2 weeks ago in a motorcamp
kitchen. The lady was about to make coffee when most of her cup of
microwaved water literally exploded out of the cup.



       RM

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2004\08\03@143106 by Gaston Gagnon

face
flavicon
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Nate Duehr wrote:
<...>
> In 63 seconds this should not happen, but be forewarned that in older
> ovens without carousels, water in a container sitting very still can
> become superheated in a microwave oven.  Upon disruption by some object
> (thermometer in this case) the superheated (above boiling point but not
> boiling) water can and will explode out of the container as it all
> instantaneously boils over, flashing to steam and covering the
> unsuspecting "scientist" with boiling water.

Look at the videos. Very impressive ... scary
http://apache.airnet.com.au/~fastinfo/microwave/videos/watervideos.html

Gaston Gagnon

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2004\08\03@233711 by Rich

picon face
It is my understanding that the two hydrogen atoms in the H20 water molecule
are at an angle of approximately 105 degrees (because the hydrogen atoms
must share at a resonance that results in such an angle.  The 2450 MHz
introduces energy into the H20 molecule because the molecule can accept the
energy due to is structure, and causes the two hydrogen atoms to be
displaced (kind of rocks them back and forth,so to speak).  It is this
regular periodic displacement which resonates that causes the water to boil
(i.e., by friction).  Ideally, the 2450 MHz will only heat the water
molecule because the water molecule can absorb the energy, whereas plastic
molecules, and may others, cannot.  Please let me know if this explanation
is unsatisfactory, or not technical enough.



{Original Message removed}

2004\08\04@011048 by Russell McMahon

face
flavicon
face
> molecules, and may others, cannot.  Please let me know if this explanation
> is unsatisfactory, or not technical enough.

Worth noting that all sorts of other non water containing materials are
variably absorbative (?) of RF at that frequency. Some plastic (very
possibly due to Hydrogen bonds also) are quite affected while others not at
all.

The classic way to get absorption is to provide a shorted turn of some sort
with some resistive loss to dissipate the energy. I've seen the top of a
glass coffee pot melted when it was microwaved (at my unwitting
recommendation :-)  ) - because there was a metal ring of about 4": ID
inside the plastic handle - who would have thought ? ;-). I was not flavour
of the week.

Plates with gold decoration around the edges also form a shorted turn and
put on an enthusiastic & impressive display of energy dissipation until the
gold gets tired and leaves.

Controlled absorption is used in eg browning plates. A standard uWave oven
may also be used to melt metal if a suitably dissipative container is used
to hold the metal.

       http://home.c2i.net/metaphor/mvpage.html

       http://home.c2i.net/metaphor/



       RM

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2004\08\04@015445 by Jinx

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> gold gets tired and leaves.

Oh, haha. Gold leaf

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2004\08\05@002813 by Rich

picon face
Any screwdriver made with ferrous material can become a magnetic screwdriver
by simply rubbing the shaft back and forth against a strong enough permanent
magnet. The magnetic field re-orders the position of the magnetic dipoles in
the ferrous material in such a way that they line up in the same direction.


{Original Message removed}

2004\08\05@003227 by Rich

picon face
You must carefully construct a research design that posits your hypothesis
and tests the null hypothesis.  Use a temperature measurement device.  There
are non-contact optical pyrometers that are quite accurate.  ALL RF IS
DANGEROUS, but it is most dangerous when one gets careless or comfortable.


{Original Message removed}

2004\08\05@003642 by Rich

picon face
Also, a special parabolic antenna design can focus the uWave at a specific
(x,y,z) point.  The energy can also be made to concentrate at that point.
These techniques are also used in optics.  You can get seriously hurt by
attempting experiments you are not ready for.


{Original Message removed}

2004\08\05@063242 by Howard Winter

face
flavicon
picon face
On Mon, 2 Aug 2004 13:17:55 -0400, Robert B. wrote:

> The way I understand it, any escaped microwaves would only heat me up.

Try holding a 5W 12V bulb between your fingers while it's running for a few minutes and see how comfortable
"only heating up" feels!

> I don't ever feel warmer when the microwave is running, therefore I am not
> very concerned.

When I got my first mobile phone (a Nokia that later was known as one of the most powerful RF radiators) I
found that if I used it against my right hear, I got a pain in my right eye.  It didn't feel warm, it hurt!
Consequently I held it to my left ear (for some reason that felt OK) but I also used it as little and for as
short a time as possible.  I have no idea if it did me any harm, but reducing the risk seemed like a good
idea!  In hindsight perhaps I should have changed the phone for one that didn't hurt earlier than I did, but
you know what they say about hindsight!

To quote the National Radiological Protection Board (the UK's watchdog on this sort of thing): "the difference
between exposure to infra-red frequencies (radiant heat) and microwaves is that the former produces surface
heating while the latter is absorbed within the body tissue thus raising its bulk temperature. Thermal damage
has been shown to occur at radiation intensities of 100 mW/cm 2 and above."  This is from:
http://www.hse.gov.uk/lau/lacs/60-3.htm

The last time I heard the legal "safe limit" in the UK was 10mW/cm2, although I believe proposed European
regulations are to reduce this, and may have already done so.

> The oven's rating is 800W, 2450MHz.  Even if all that
> radiation escaped in a concentrated beam, it would still be far below many
> commercial microwave transmitters.

I think you're wrong.  When the firm I used to work for needed a microwave communications link, it was limited
to 10mW.

> I've heard stories of tech's sitting
> near the microwave transmitter beams to keep warm in the winter, so I'm
> still having trouble believing a little microwave radiation leakage could
> actually do any damage.

Have you heard ot the Darwin Awards?  Just because people do things it doesn't mean it's safe!  :-)  When I
was a kid there were machines in shoe shops where you could put your feet into slots in the bottom, and look
down into the top and see your feet inside your shoes - they were always-running X-ray machines.  My mother
told me to stay away from them because they "weren't good for you" - so I did, and I'm rather glad that my
mother's intuition was ahead of scientific thinking at the time!

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@063242 by Howard Winter

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Lawrence,

On Mon, 2 Aug 2004 13:09:20 -0500, Lawrence Lile wrote:

> Don't bash in the door - get inside the thing and take
the magnet out of it.

How big *is* this microwave?  :-)))

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@065355 by Howard Winter

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Robert,

On Mon, 2 Aug 2004 15:52:29 -0600, Robert Rolf wrote:

> What always amuses me about the 'panicked public' is that
> the body's intrinsic operating voltages (across nerve
> membranes) are on the order of 50kV/meter. ORDERS of magnitude
> above what you would get from typical external EM fields.
> Muscles also produce 100's of millivolts, again over tiny
> scales, so you have low kV/meter all the time (remember that
> your heart is beating all the time and you do have to breath).

And yet 35mA is regarded as the safe limit for an electric shock...

> External EM fields are down in the noise compared to what
> body cells are exposed to on a continuous basis.
> And the body electrolytes are highly conductive, highly
> attenuating higher RF frequencies with depth.

"Attenuating" must mean "absorbing", unless you know another way to get rid of energy?

> And if the 'radiation' is non-ionizing, the worst that can
> happen is that you get warmed up a bit, which is not a problem
> since your blood carries away the heat.

On a major scale, yes, but if the energy concentration is high enough om a small area you may get local
boiling which would destroy cells.

>The only body part
> that is not protected by this cooling process is the lens and
> cornea of the eye. Cook those (42C+) and you DO have a problem,
> but nothing fatal.

I don't regard going blind as something I'd like to happen, even if it's "non fatal"!

> I work in Neuroscience, and have reviewed the literature because
> of the RF excited implanted stimulators we use for rehab. FES.
>
> There are also TNS (Transcranial Neural Stimulators) which create
> kilo Tesla fields to directly stimulate deep brain regions.

I was never much good at magnetism, which I believe falls off rapidly with distance anyway (I don't think you
can "transmit" magnetic energy - I'm more concerned about the RF "electric" side of it.

> None of the 10's of thousands of patients exposed to these
> fields has ever been reported as having come down with brain
> cancer or related diseases, and given the sample space and EM
> strength, this SHOULD have happened if there were a causal
> relationship.

There has been a study in Poland which correlates microwave exposure of military personnel with cancers - see:
http://www.feb.se/EMFguru/Current-Messages/emf-cancer.html

> And lets not forget the statistics of TENS OF MILLIONS of
> cellular phone users, and their NOT having brain cancers
> at anything above random rates.

Worldwide it's hundreds of millions, but mobile phones haven't been around very long, and cancer takes time to
happen - nobody (not even the anti-RF evangelists) says that using a mobile phone today will kill you
tomorrow.  Both my parents smoked from their teens - my father survived to age 67 before it killed him, my
mother to 51.  I'm 50, and *really* glad that smoking never seemed like a good idea to me!  During WWII Brits
(at least) were encouranged to smoke by the government, who thought that it would produce a calmer population,
more able to cope with the stresses of wartime...

Cheers,

Howard Winter
St.Albans, England

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2004\08\05@071922 by Howard Winter

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Robert,

On Mon, 2 Aug 2004 19:51:02 -0600, Robert Rolf wrote:

> Over the years manufacturers have used several
different methods to rate
> the output wattage of microwave ovens.
>...<

Thanks for the rating-procedure - I only had a
thermometer with whole-degree C reading, and it showed
an 8C rise, giving 560W plus or minus 70W.  It's an old
microwave and I don't know what its rating was sold as,
but I know the real figure now!

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@073418 by Howard Winter

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Nate,

On Tue, 3 Aug 2004 02:34:39 -0600, Nate Duehr wrote:

> In 63 seconds this should not happen, but be forewarned that in older
> ovens without carousels, water in a container sitting very still can
> become superheated in a microwave oven.  Upon disruption by some object
> (thermometer in this case) the superheated (above boiling point but not
> boiling) water can and will explode out of the container as it all
> instantaneously boils over, flashing to steam and covering the
> unsuspecting "scientist" with boiling water.

This can happen (and has) with reheating cups of coffee and the like, but in this case we're talking about a
litre of water, and the maths show that to heat it from 20C to 100C in the 63secs you'd need 5600W and as far
as I know there are no kitchen microwaves that powerful!  (Assuming 100% efficiency that would need a 50A
supply in the US, a 24A supply in Europe, and I believe that's pretty unusual for domestic sockets :-)

Cheers,

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2004\08\05@073624 by Howard Winter

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Russell,

On Tue, 3 Aug 2004 21:47:39 +1200, Russell McMahon
wrote:

> While undisturbed the heated water starts to
transition between solid state
> and gaseous state

I don't think you meant "solid"  ;-)

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@075741 by Russell McMahon

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> > While undisturbed the heated water starts to
> transition between solid state
> > and gaseous state
>
> I don't think you meant "solid"  ;-)


True.
Such an arrangement would be sublime :-)
(Now with a little adjustment of the pressure ... )


       RM

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2004\08\05@082932 by Lawrence Lile

flavicon
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>Just because people do things it
> doesn't mean it's safe!  :-)  When I
> was a kid there were machines in shoe shops where you could put your
feet
> into slots in the bottom, and look
> down into the top and see your feet inside your shoes - they were
always-
> running X-ray machines.  My mother
> told me to stay away from them because they "weren't good for you" -
so I
> did, and I'm rather glad that my
> mother's intuition was ahead of scientific thinking at the time!
>

Stunts like this are probably why my father had leukemia at 35.  He was
in medical school right after WWII, when "radiation" and "Hazard" were
never used in the same sentence. Had a lot of access to X ray equipment.


-- Lawrence Lile, P.E.
Electrical and Electronic Solutions
Project Solutions Companies
http://www.projsolco.com

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2004\08\05@083346 by Lawrence Lile

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I have tried to make mag screwdrivers with the rubbing trick, however
heating them and letting them cool while stuck to a strong magnet seems
to make a better and longer lasting magnet out of them.  I am sure there
are plenty of other ways.



-- Lawrence Lile, P.E.
Electrical and Electronic Solutions
Project Solutions Companies
http://www.projsolco.com

> {Original Message removed}

'[OT:] WIFI Waveguide antenna'
2004\08\05@084422 by Howard Winter

face
flavicon
picon face
David,

On Mon, 2 Aug 2004 08:34:22 -0500, David VanHorn wrote:

> At 07:34 AM 8/2/2004, Howard Winter wrote:
>
>...<
> You want something that has 50ohm impedance, which rules out TV and Satellite (75 ohm).
>
> Actually, 75 ohm cable is less lossy up high (in general) and might be a better choice.
> Some antennas match better to 75 than to 50, and at the card end, a 1.5-1 VSWR isn't a big deal.  Far more
important that the antenna be resonant.  Tough to know up here without specialized equipment.

I think the problems of mismatch may go far beyond the SWR, and the reduction of loss may not matter because
WiFi is a fast duplex system.  It could be that when transmitting stops the ringing caused by the mismatch at
both ends may still be strong enough that when the card switches to receiving it's deafened and doesn't hear
the reply.  This is a guess based on no knowledge of the hang-time parameters of WiFi!

A number of years ago the office I worked in had a 10-base-T network (50-ohm coax daisy-chained, I think) and
I got a call from a secretary saying that if I didn't get there soon and fix it, she'd throw her computer out
of the window!  Performance had degraded to the point where it took 2 minutes to open a file (in WordPerfect
for example).  I connected up a Time Domain Reflectometer and found that there were reflections that shouldn't
have been there.  Traced along the cable and found that someone had added their machine to the network, using
a piece of 75-ohm cable (about 3m long) and this was causing enough reflections to bring the whole network to
its knees!  And this was with everything just wired together, not listening for an incoming signal from the
"aether"  :-)  I've had a healthy respect for impedance matching ever since.

Cheers,


Howard Winter
St.Albans, England

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\05@084632 by Howard Winter

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Lawrence,

On Thu, 5 Aug 2004 07:28:41 -0500, Lawrence Lile wrote:

> I have tried to make mag screwdrivers with the rubbing trick, however
> heating them and letting them cool while stuck to a strong magnet seems
> to make a better and longer lasting magnet out of them.

But it's a good idea if you can thermally insulate it from the magnet - heating a magnet is a really good way
to weaken or destroy it (I've just realised I remember that from an exam question at school about 35 years ago
:-)

Cheers,


Howard Winter
St.Albans, England

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'[OT:] WIFI Waveguide antenna'
2004\08\05@085044 by Howard Winter

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Robert,

On Mon, 2 Aug 2004 11:12:27 -0400, Robert B. wrote:

> Sorry, I just pulled a scrap out of the basement.  I'm pretty sure it's RG58
> though, and either way it looks like it seriously attenuates my signal :(

Ah - is it a damp basement by any chance?  Were the connectors already fitted or did you fit them yourself?
If there's water in the cable it *will* really attenuate!

Cheers,


Howard Winter
St.Albans, England

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\05@085250 by Robert B.

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How much are you heating them?  Hopefully not enough to destroy the temper,
which is done surprisingly easily.  Temperatures as low as 150C are enough
to affect the grain structure of steels.

{Original Message removed}

'[OT:] WIFI Waveguide antenna'
2004\08\05@085912 by Howard Winter

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Mike,

On Mon, 2 Aug 2004 16:42:52 +0100, Michael Rigby-Jones
wrote:

>  I just bought an 802.11G dongle (need USB2 to get
full bandwidth) for just over £20

Can I ask what make this is and where you got it,
please?

Cheers,


Howard Winter
St.Albans, England

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2004\08\05@090121 by Robert B.

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The cable is bone dry, and there were no connectors fitted so I put them on
myself.  I'll openly admit it's a hacked together job from materials I had
on hand at the time to see if the cantenna would pick up a signal.  The
signal is surprisingly good considering all the problems people have pointed
out with it.  Now that final exams are over I'll be working to properly
match everything, and maybe build one of those USB-dongle dishes just for
comparison.

On a side note, I was testing the ol' deathray microwave to see if it did
interfere with the network, and yeah it brings it down real quick.  My
neighbor's wifi signal (different neighbor than the 2.4ghz phone) is
attenuated significantly as well, but that might be just on my end.  I'll
have to ask him if he's noticed any abnormalities in his network services
around dinner time. ;-)

{Original Message removed}

2004\08\05@090535 by hael Rigby-Jones

picon face
>-----Original Message-----
>From: pic microcontroller discussion list
>[PICLISTSTOPspamspamKILLspamMITVMA.MIT.EDU] On Behalf Of Howard Winter
>Sent: 05 August 2004 13:59
>To: @spam@PICLIST.....spamspamMITVMA.MIT.EDU
>Subject: Re: [OT:] WIFI Waveguide antenna
>
>
>Mike,
>
>On Mon, 2 Aug 2004 16:42:52 +0100, Michael Rigby-Jones
>wrote:
>
>>  I just bought an 802.11G dongle (need USB2 to get
>full bandwidth) for just over £20
>
>Can I ask what make this is and where you got it,
>please?
>

Posted this before for Alan:


http://www.ebuyer.co.uk (quickfind code 63002) is the actual device I
bought. However, I have just checked and the product I bought seems to have
gone up to £27.99.  Not unusual for Ebuyer however, they do seem to have a
very "flexible" pricing policy.  Worth keeping an eye on it though as I've
known prices to go down shortly after they've been increased.

There is an alternative device for £22.99 (quickfind code 60710) that is a
little bit larger and has an external antenna which may well be better if
you aren't intending on putting it in front of a dish.
Note that they are described as being of "Ebuyer" brand, but in relality
they simply sell whichever product they can get the cheapest, which may or
may not be in retail packaging.  The one I bought was made by Origo
http://www.origo2000.com/show-prds.php?ID_NUM=80

Regards

Mike

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'[OT:] WIFI Warning'
2004\08\05@092954 by Bob Axtell

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With all this talk of (and activity about) WIFI: have you noticed a
conspicuous silence from the Feds about it? No complaints about
encryption, or interference with airplane radios, etc, or any other
smoke and fog one normally expects to hear from Big Brother?

It's because they welcome WIFI with open arms; they've cracked its
encryption big time, and its as secure as a trainwreck. A Fed's dream:
all that data, readable w/o a court order, all ya gotta do is just pluck
it out of the air.

Watch out guys. Assume that everything you design is readable. Just a
friendly warning.

--Bob

Robert B. wrote:

{Quote hidden}

> {Original Message removed}

'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\05@094822 by M. Adam Davis

flavicon
face
Howard Winter wrote:

>And yet 35mA is regarded as the safe limit for an electric shock...
>
>
>
>
Everytime I see this, " XXmA is the limit", I think back to all the
different opinions.  The lowest I've seen is 10mA, but generally the
only reason these shocks are not safe is because they /might/ disrupt
the pace of the heartbest.  Thus they all pretty much have to be through
the heart (hand to hand, hand to foot, head to anything, etc).

Of course this has little to do with the voltage applied - you can have
kV of potential across your body and only uA of current, and under 100V
with over 100mA of current.  You could have 1A going from your thumb to
your forefinger without killing yourself, or foot to foot, though I
imagine it would be pretty painful just before you blacked out. :-)

Not only is the current a 'soft' variable, but timing is also critical,
and voltage waveform has a big effect.  It has to be applied at the
right time to cause the heart to fibrillate (it's very rare, I
understand, for the heart to stop beating completely - usually it just
beats ineffectively, which has the same end result).  AC is sometimes
not as bad as DC because it tries to travel along the outside of the
conductor, and little current may go through the heart.

Doesn't mean I like to touch the electric horse fence, though.  Worst
way to see if one is working - disconnect both terminals, place one hand
on one terminal and one hand on the other.  Feels like a 20 pound sledge
hammer right in the chest - had to sit down for 30 minutes after that
stupidity, and can only hope it didn't cause any sort of permanent
damage that will come back to haunt me.

-Adam

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2004\08\05@102314 by Howard Winter

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On Thu, 5 Aug 2004 09:48:05 -0400, M. Adam Davis wrote:

> Howard Winter wrote:
>
> >And yet 35mA is regarded as the safe limit for an electric shock...
> >
> Everytime I see this, " XXmA is the limit", I think back to all the
> different opinions.

Yes, but you have to have a figure to design an RCCD (safety device to break the circuit when some of the
current gets away) and 35mA / 35mS is easy to remember!  :-)

My point was that quoting electric field density is misleading since that is only one measurement of the many
possiblilities.  There's much more heat-energy in a bath of warm water than in a red-hot nail, but I know
which one I'd rather touch!

> The lowest I've seen is 10mA, but generally the
> only reason these shocks are not safe is because they /might/ disrupt
> the pace of the heartbest.

They can also cause physical damage, internal burns, cell disruption, and disruption of nerves' ability to
function.

> Thus they all pretty much have to be through
> the heart (hand to hand, hand to foot, head to anything, etc).

It's not easy to decide where the current will travel before you get the shock (presumably you'd decide not to
get it at all, otherwise) although the old "keep one hand in your pocket" rule for working on high voltage
gear is a Good Thing.  But the designer of safety equipment has to assume the worst.

> Of course this has little to do with the voltage applied - you can have
> kV of potential across your body and only uA of current,

Hurts like hell though!  A shock from a spark plug really does make you jump, but doesn't do damage unless it
causes you to pull your hand away into something hot or rotating.  Many years ago I knew someone who "didn't
feel" the shock from a spark plug - I have no idea how this can happen - and he would have one finger on the
plug-cap, and a finger on the other hand producing sparks to the bodywork, without even flinching.  If people
asked if it hurt, he would get hold of their hand and repeat the procedure... I never fell for *that* one!

> and under 100V
> with over 100mA of current.  You could have 1A going from your thumb to
> your forefinger without killing yourself, or foot to foot, though I
> imagine it would be pretty painful just before you blacked out. :-)

Quite!  That's why you should stand with your feet together if you're outside during a thunderstorm - or run
like mad to get inside!  :-)  But the differential voltage across the ground has been known to kill cattle,
since their front and back legs are a long away apart and their heart tends to be on the way between.

I once heard the saying:  "It's the volts that jolts, it's the mill's that kills".  The grammar is rubbish but
it's technically correct, and memorable!

>...<
>
> Doesn't mean I like to touch the electric horse fence, though.  Worst
> way to see if one is working - disconnect both terminals, place one hand
> on one terminal and one hand on the other.  Feels like a 20 pound sledge
> hammer right in the chest - had to sit down for 30 minutes after that
> stupidity, and can only hope it didn't cause any sort of permanent
> damage that will come back to haunt me.

The advice in cases like this is to go to a doctor/hospital and get checked out.  People have been known to
survive a shock at the time, only to die a day or two later due to creeping failure of the heart muscle,
started by the shock.  I know it's easy to say that sitting here, but it's worth remembering in future, and
yes, I've had a mains shock (240V 50Hz here) that left me feeling dazed and "abent-minded" for some time
afterwards, and I didn't see anyone about it either.  But I will next time!

Cheers,


Howard Winter
St.Albans, England

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'[OT:] WIFI Warning'
2004\08\05@115005 by Nate Duehr

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Bob Axtell wrote:

> With all this talk of (and activity about) WIFI: have you noticed a
> conspicuous silence from the Feds about it? No complaints about
> encryption, or interference with airplane radios, etc, or any other
> smoke and fog one normally expects to hear from Big Brother?
>
> It's because they welcome WIFI with open arms; they've cracked its
> encryption big time, and its as secure as a trainwreck. A Fed's dream:
> all that data, readable w/o a court order, all ya gotta do is just pluck
> it out of the air.
>
> Watch out guys. Assume that everything you design is readable. Just a
> friendly warning.

There are a number of open-source packages that will unencrypt standard
WEP on a standard laptop.  Nothing surprising there, if you're paying
attention to what's going on.

There are proper ways to secure WiFi and other wireless connections.
Using the built in encryption is not one of them.

--
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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\05@115414 by Robert Rolf

picon face
Rich wrote:
> You must carefully construct a research design that posits your hypothesis
> and tests the null hypothesis.  Use a temperature measurement device.  There
> are non-contact optical pyrometers that are quite accurate.  ALL RF IS
> DANGEROUS, but it is most dangerous when one gets careless or comfortable.

So you don't use cell phones or Wi-Fi or Bluetooth or cordless
phones or ANY form of RF receiver?? What about microwave ovens?

How can you say "ALL RF IS DANGEROUS" when we live in a sea
of low power RF, yet we're still alive?
I can also kill you with pure distilled water.

Hyperbole will get your arguments quickly dismissed.
Perhaps you meant
'High Power' RF CAN BE dangerous if not treated with respect.

R

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2004\08\05@141229 by John Ferrell

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> Doesn't mean I like to touch the electric horse fence, though.  Worst
> way to see if one is working - disconnect both terminals, place one hand
> on one terminal and one hand on the other.  Feels like a 20 pound sledge
> hammer right in the chest - had to sit down for 30 minutes after that
> stupidity, and can only hope it didn't cause any sort of permanent
> damage that will come back to haunt me.

Not a good idea to Pee on one either!

John Ferrell
http://DixieNC.US

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'[OT:] WIFI Warning'
2004\08\05@142021 by M. Adam Davis

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Nate Duehr wrote:

>
> There are a number of open-source packages that will unencrypt standard
> WEP on a standard laptop.  Nothing surprising there, if you're paying
> attention to what's going on.
>
Yes, but if the key is chosen well then the attacker needs to capture
several million packets in order to discover the key.  This can take
days or weeks on a low data rate network, meaning the attacker or their
equipment has to be nearby - close enough to record both sides of the
conversation (ie, not just pointing a directional antenna at the AP).

WEP is reasonably secure, but it can be broken by someone with $50 of
equipment, a laptop, and some time.  Your next door neighbor is more of
a threat to you than the FBI, NSA, or other TLA.

> There are proper ways to secure WiFi and other wireless connections.
> Using the built in encryption is not one of them.

Just like code protecting a uController, you need to be aware of the
ease of breaking the code, and the cost of securing it.  It isn't worth
it to most people to do more than the simple WEP to keep out most of the
casual crackers.

Besides, the Gov't is much lower tech for most investigations.  They'll
have an easier time tossing your house, taking anything electronic, and
sending it off for analysis then setting up a tap (wireless, ethernet,
cable, phone, etc) and listening for days/weeks/months.  They'll only
put that effort into it if the target is particularily worthwhile.

Of course, I could be wrong.  Or perhaps I'm a government plant, trained
at leading everyone into a false sense of security while /the entire
piclist mebership is being tapped!!!/  (insert evil laughter)  Yes, even
you in Australia and Bulgaria.  All your base are belong to us*.

-Adam

*Actually, the US gov't was interested in taking over the world, but
they can't compete with the likes of McDonalds so they've pretty much
given up.

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2004\08\05@144722 by Dwayne Reid

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At 09:50 AM 8/5/2004, Nate Duehr wrote:

>There are proper ways to secure WiFi and other wireless connections.
>Using the built in encryption is not one of them.

Hi there, Nate.

Can you suggest a starting point for me to learn about WiFi security?

I'm thinking seriously about getting a WiFi rig for use at home before
trying to deploy a system for here at work.  Security is one of my main
concerns and I'm not comfortable with installing a wireless network at work
until I have learned enough to secure it.

dwayne

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Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
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2004\08\05@150137 by Bob Axtell

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M. Adam Davis wrote:

> Besides, the Gov't is much lower tech for most investigations.  They'll
> have an easier time tossing your house, taking anything electronic, and
> sending it off for analysis then setting up a tap (wireless, ethernet,
> cable, phone, etc) and listening for days/weeks/months.  They'll only
> put that effort into it if the target is particularily worthwhile.
>
> *Actually, the US gov't was interested in taking over the world, but
> they can't compete with the likes of McDonalds so they've pretty much
> given up.

Being an American, I'm constantly amazed at what comes out of Washington
these days. I'm convinced that there ARE people in the Fed bureaucracy
that would love to take over the world... but one they grabbed it, could
they actually be able to RUN it any better than they run it here? YOU
decide!

--Bob, whose email will be probably be delayed by Homeland security again...



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2004\08\05@151214 by David VanHorn

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>
>Being an American, I'm constantly amazed at what comes out of Washington
>these days. I'm convinced that there ARE people in the Fed bureaucracy
>that would love to take over the world... but one they grabbed it, could
>they actually be able to RUN it any better than they run it here? YOU
>decide!

IIRC, the IRS wasn't able to turn a profit at the Mustang ranch...

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2004\08\05@151215 by David VanHorn

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At 01:46 PM 8/5/2004, Dwayne Reid wrote:

>At 09:50 AM 8/5/2004, Nate Duehr wrote:
>
>>There are proper ways to secure WiFi and other wireless connections.
>>Using the built in encryption is not one of them.
>
>Hi there, Nate.
>
>Can you suggest a starting point for me to learn about WiFi security?

There's not a lot to it.
Turn encryption on, change keys as often as practical.

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2004\08\05@153122 by Matt Pobursky

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On Thu, 5 Aug 2004 14:12:12 -0500, David VanHorn wrote:
> IIRC, the IRS wasn't able to turn a profit at the Mustang ranch...

Which is amazing, since the IRS is already in the same business... ;-)

Matt Pobursky
Maximum Performance Systems

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2004\08\05@153741 by Nate Duehr

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M. Adam Davis wrote:

[snippedy snip snip]

> WEP is reasonably secure, but it can be broken by someone with $50 of
> equipment, a laptop, and some time.  Your next door neighbor is more of
> a threat to you than the FBI, NSA, or other TLA.


Yes, I understand this - I was attempting to thwart the implied threat
in the original warning that *only* the NSA could break wireless
encryption.  Any teenager can do it with pre-written software these
days.  That's all I was saying.

[snip happens]

> Of course, I could be wrong.  Or perhaps I'm a government plant, trained
> at leading everyone into a false sense of security while /the entire
> piclist mebership is being tapped!!!/  (insert evil laughter)  Yes, even
> you in Australia and Bulgaria.  All your base are belong to us*.

LOL!

> -Adam
>
> *Actually, the US gov't was interested in taking over the world, but
> they can't compete with the likes of McDonalds so they've pretty much
> given up.

I thought that was $tarbuck$.  Birthplace of bulk god-awful coffee for
$4 a cup.  (And the staff has the verve to put out a TIP jar!  NICE!)

A recent wardriving session (if you can even call it that... I put the
laptop with a standard 802.11g card in the PCMCIA slot and drove home...
no detours, no external antennas... not even trying) found 21 open
access points with zero encryption between my work and home.  Who cares
if WEP is crackable if no one even turns it on?

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2004\08\05@155027 by Nate Duehr

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Dwayne Reid wrote:

> Hi there, Nate.
>
> Can you suggest a starting point for me to learn about WiFi security?
>
> I'm thinking seriously about getting a WiFi rig for use at home before
> trying to deploy a system for here at work.  Security is one of my main
> concerns and I'm not comfortable with installing a wireless network at
> work
> until I have learned enough to secure it.

Hmmm... the usual network security sites...

http://www.sans.org
http://www.securityfocus.com

Probably the best places to start.  SANS probably has some whitepapers
written by their students that cover the topic deeply.  (As well as just
about every other network/computer security topic under the sun.  In
order to gain an advanced SANS certification, students are required to
publish a practical security document as part of the certification.
They're all posted on the website, and free to read if you register with
them.)

A Google search turned up:
http://www.wi-fi.org/OpenSection/secure.asp?TID=2

Which looks useful for definitions.  A bit too much like "marketing" or
sales information though.

Most corporate wireless installations I've seen (two large ones) were
done with the wireless network being "untrusted" and the users having to
connect to a hardware VPN router using a VPN client from their machines
before they were really "part of the internal network".  Just like if
they had connected from home to the work network.

At the very least:  Use WPA (newer version of WEP with rotating keys,
and other fun) and turning off "Beaconing" on your Access Point is
probably "relatively" secure for a home network.   Keep up with your AP
vendor's latest firmware releases if they have any.  Those two will
generally keep anyone casually sniffing for wireless networks away.

Other techniques that work well in home networks but aren't as easy to
implement in corporate ones is the use of natural RF shielding... an
example... if you live in a house -- put the AP in the basement!  Keeps
the RF generally on your property and makes it a lot harder to sniff it
from anywhere other than your front and back lawn.  ;-)

I'll look around for a better all-encompassing primer on WiFi
security... so far I can't think of one that would cover everything or a
FAQ that would.

--
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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\05@160313 by Robert Rolf

picon face
John Ferrell wrote:

>>Doesn't mean I like to touch the electric horse fence, though.  Worst
>>way to see if one is working - disconnect both terminals, place one hand
>>on one terminal and one hand on the other.  Feels like a 20 pound sledge
>>hammer right in the chest - had to sit down for 30 minutes after that
>>stupidity, and can only hope it didn't cause any sort of permanent
>>damage that will come back to haunt me.
>
>
> Not a good idea to Pee on one either!

"Mythbusters" (a TV show on Discovery Channel Can)
proved that you need not worry about this.
Your pee stream always breaks up into droplets by
time it could hit the fence (or third rail).

You basically need a garden hose to get enough volume to
have a continuous stream.

R

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2004\08\05@180010 by Lawrence Lile

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face
That is not what my friend said when I watched him try it (he was 8 and
stupid, I was 6 and stupid but not that stupid).  Maybe he was closer to
the ground, but it gave him quite a wallop.
> > Not a good idea to Pee on one either!
>
> "Mythbusters" (a TV show on Discovery Channel Can)
> proved that you need not worry about this.
> Your pee stream always breaks up into droplets by
> time it could hit the fence (or third rail).
>
> You basically need a garden hose to get enough volume to
> have a continuous stream.
>
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2004\08\05@182742 by David VanHorn

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At 04:56 PM 8/5/2004, Lawrence Lile wrote:

>That is not what my friend said when I watched him try it (he was 8 and
>stupid, I was 6 and stupid but not that stupid).  Maybe he was closer to
>the ground, but it gave him quite a wallop.

What a brilliant example of the pitfalls of simulation vs prototyping. :)

(bonus points for getting HIM to try it :)

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2004\08\05@230429 by Rich

picon face
----- Original Message -----
From: "Robert Rolf" <.....Robert.Rolf.....spamRemoveMEUALBERTA.CA>
To: <spam_OUTPICLISTTakeThisOuTspamEraseMEMITVMA.MIT.EDU>
Sent: Thursday, August 05, 2004 11:43 AM
Subject: Re: [OT:] Microwave ovens was WIFI Waveguide antenna


> Rich wrote:
> > You must carefully construct a research design that posits your
hypothesis
> > and tests the null hypothesis.  Use a temperature measurement device.
There
> > are non-contact optical pyrometers that are quite accurate.  ALL RF IS
> > DANGEROUS, but it is most dangerous when one gets careless or
comfortable.
>
> So you don't use cell phones or Wi-Fi or Bluetooth or cordless
> phones or ANY form of RF receiver?? What about microwave ovens?
>
> How can you say "ALL RF IS DANGEROUS" when we live in a sea
> of low power RF, yet we're still alive?

Rich answered:

I agree that the wording is too general.  But all RF exposure is potentially
dangerous and some is absolutely dangerous.  I know of a fellow that used to
tune antennas for radio stations.  He would call the control room and have
them kill the power before he left the tower.  One time the power was left
on and as he jumped from the concrete base to the ground a RF arc burned him
to death, presumably before he hit ground.  I, myself, have had several
painful RF burns from working on low power transmitters.  They are quite
painful and seem to burn from the inside out.  (Of course I did not prove
that, but it felt like it.)  My point was really that one must exercise
great caution when working with RF, just as when working with high voltage.
I once saw a dude short out some capacitors while I hollered "NO Don't DO
THAT" to him.  The capacitors exploded and the dude was hurt pretty bad and
of courrse the screw driver was melted.   I have learned to respect the
dangers involved in science.  Madam Curie was unfortunately unaware of the
hazards of radiation, the inventor of morphine died from addiction and the
stories abound.

I know the axiom the the negation of a universal quantifier is an
existential qualifier, so if I was generalizing hastily, I accept that
criticism.  But I am comfortable with the phrase all RF is "potentially"
dangerous.

While we do know that radiation intensity decreases as a square function
with respect to distance, we have not yet established a golden standard for
an individual of a given mass, although there are some recommendations.

> I can also kill you with pure distilled water.

Rich replied:
Anyone can die from drinking an excessive amount of water.  So, what does
that prove about radiation?
>
> Hyperbole will get your arguments quickly dismissed.
> Perhaps you meant


> 'High Power' RF CAN BE dangerous if not treated with respect.

Replied again:
If I may say so, LOW POWER RF CAN BE DANGEROUS if not treated with respect
or proper management.  Furthermore, the RF frequency is a definite factor,
besides power.

Rich also says:
Thank you for the discussion.  I find such discussions informative and
generally speaking, useful.
>
> R
>
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2004\08\05@235739 by Russell McMahon

face
flavicon
face
> > How can you say "ALL RF IS DANGEROUS" when we live in a sea
> > of low power RF, yet we're still alive?

> I agree that the wording is too general.  But all RF exposure is
potentially
> dangerous and some is absolutely dangerous.

Prudent avoidance.
Practice prudent avoidance.
Chorus:    Prudent ......

Use solder, petrol, diesel (if you must), RF, DC, AC, PICs ;-), alcohol,
food, ....

Be aware that all are dangerous to an unknown and variable extent.
Enjoy life, have fun, don't be paranoid, do be aware that real dangers exist
all over, ventilate work places, stay away from diesels (produce amongst the
most cancerous particles known to man), keep the mains powered alarm clock
well away from your head when sleeping,  do do an EM sweep of your house
once every few years, don't live under hv power lines or within a few
lots/sections thereof. look both ways when crossing, do not spindle staple
fold or mutilate, drink alcohol sparingly, keep one hand in pocket, the
brighter the plant colour the better it is for you (usually)(don't eat too
much), don't sleep too much or too little (however long that may be), too
fat will kill you quicker, too thin will too, avoid very high or very low
anything diets, you need some saturated fats to keep your ldl:hdl ratio
good, practice moderation in everything - but do so with moderation, don't
stare into operating microwave ovens, avoid badly burned food, avoid contact
with high temperature combustion products (motor oil etc), be aware that 12
VDC has killed by electric shock in extreme conditions, don't sniff PICs
(except in BGA or similar leadless packages),  consider not living in
congested / smoggy cities (but remember what happened at Lockerbie), fill in
the intentions book in every hut, emergency satellite locator beacons are
cheap to hire, excess alcohol and boating is a fatal mix, if you have a $10
head then buy a $10 helmet, death is nature's way of telling you to slow
down, eat broccoli, enjoy life, have fun, don't be paranoid, ...

:-)

This could be quite a fun list when complete.



       RM

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2004\08\06@043300 by Alan B. Pearce

face picon face
>> Not a good idea to Pee on one either!
>
>"Mythbusters" (a TV show on Discovery Channel Can)
>proved that you need not worry about this.
>Your pee stream always breaks up into droplets by
>time it could hit the fence (or third rail).

Try telling that to a past colleague of mine. he reckoned that although it
didn't actually get welded shut, it sure felt like that is what happened,
such was the pain :))))))))))

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2004\08\06@044335 by hael Rigby-Jones

picon face
>-----Original Message-----
>From: pic microcontroller discussion list
>[EraseMEPICLISTspamBeGonespamKILLspamMITVMA.MIT.EDU] On Behalf Of Russell McMahon
>Sent: 06 August 2004 04:56
>To: RemoveMEPICLISTspamBeGonespamspamMITVMA.MIT.EDU
>Subject: Re: [OT:] Microwave ovens was WIFI Waveguide antenna
>
> eat broccoli, enjoy life

Those two are mutualy exclusive for me! :o)

Mike

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2004\08\06@051940 by Russell McMahon

face
flavicon
face
> > eat broccoli, enjoy life

> Those two are mutually exclusive for me! :o)

I'm not a great Broccoli fan. But it is thought that it is one of the most
useful vegetables available due to various arcane components. I eat a little
in Chinese food occasionally and find with time that it becomes almost
bearable :-)

While on the topic - beware the processed vitamins route. Some of these have
their place no doubt BUT it appears that at least some which are
unquestionably effective when taken in their natural form, actually produce
adverse results when extracted and taken as a "supplement". One such is Beta
Carotene. So I'm afraid it's going to have to be carrots with your Broccoli
:-) !!!

Tomato cooked or raw has gotta be good for you fwiw.

Brighter the colour, better the result as a VERY rough rule of thumb.

Green tea can't hurt (I hope :-) ).

Ginkgo Biloba I'm not yet convinced about :-(





       R "by no means a health food freak" M

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'[OT:] WIFI Warning'
2004\08\06@055954 by Howard Winter

face
flavicon
picon face
Dave,

On Thu, 5 Aug 2004 14:12:56 -0500, David VanHorn wrote:

> >Can you suggest a starting point for me to learn
about WiFi security?
>
> There's not a lot to it.
> Turn encryption on, change keys as often as practical.

There's also: Choose as high a number of bits for the
encryption key that you can.  As I understand it, it's a
geometric progression - 128 bits isn't twice as hard as
64, it's 64 times as hard.

Some, generally older, hardware will only do the lower
numbers of bits (I think it started at 40 then went up
to 64) - I personally wouldn't use any less than 128
bits.

Cheers,


Howard Winter
St.Albans, England

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2004\08\06@060215 by Howard Winter

face
flavicon
picon face
Nate,

On Thu, 5 Aug 2004 13:37:08 -0600, Nate Duehr wrote:

> A recent wardriving session (if you can even call it
that... I put the
> laptop with a standard 802.11g card in the PCMCIA slot
and drove home...
> no detours, no external antennas... not even trying)
found 21 open
> access points with zero encryption between my work and
home.  Who cares
> if WEP is crackable if no one even turns it on?

As a matter of interest, what software did you use?  The
stuff I've seen wouldn't record this for you over a
session, just show you it "live".  I presume you weren't
operating it yourself while driving!  :-)

Cheers,

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2004\08\06@061653 by Russell McMahon

face
flavicon
face
> > >Can you suggest a starting point for me to learn
> about WiFi security?
> >
> > There's not a lot to it.
> > Turn encryption on, change keys as often as practical.
>
> There's also: Choose as high a number of bits for the
> encryption key that you can.  As I understand it, it's a
> geometric progression - 128 bits isn't twice as hard as
> 64, it's 64 times as hard.


Probably ~~ 2^64 times as hard.

64 bits can be cracked in hours using eg ?Net Stumbler.
Last time I read up on this (over a year ago) 128 bits was theoretically
crackable but in practice was believed to be essentially secure to all but
perhaps the experts with a serious grudge and very serious computing power.
Has this changed since then?



       RM

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\06@070538 by Howard Winter

face
flavicon
picon face
Robert,

Electric fences...

On Thu, 5 Aug 2004 13:53:05 -0600, Robert Rolf wrote:

> > Not a good idea to Pee on one either!
>
> "Mythbusters" (a TV show on Discovery Channel Can) proved that you need not worry about this.
> Your pee stream always breaks up into droplets by time it could hit the fence (or third rail).

Well I for one wouldn't trust my life (or... anything!) to this.  If the fence-wire is high/close enough I'm
sure the stream will still be intact.  Third rail *from a station platform* is probably safe, but if you're
standing beside the track, with the permanent way rising above you so the top of the conductor rail is quite a
bit above your feet, I certainly wouldn't try it!  Nor would I try it from a bridge onto an overhead wire
(third rail supplies here are 750V, overhead wires are at 25kV and kids occasionally get themselves killed by
dangling things over bridges on string).

> You basically need a garden hose to get enough volume to have a continuous stream.

Oh, you mean you hav...  <redfaced>  ;-)

I may try measuring unbroken-stream at some convenient point, and reporting back.

Cheers,

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2004\08\06@072653 by Howard Winter

face
flavicon
picon face
Rich,

On Thu, 5 Aug 2004 23:04:26 -0400, Rich wrote:

> While we do know that radiation intensity decreases as a square function with respect to distance

I've been thinking about this (always dangerous!) and it's based on isotropic radiation, isn't it?  The
emission spreads outwards in an expending sphere-shape, so the density reduces as the area of the sphere
increases, which is proportional to square-of-radius (QED).

BUT!  What if the radiator isn't isotrpoic, but has "gain" in a particular direction?  Surely the whole point
of a gain antenna is to increase the energy in the wanted direction at the expense of the other directions, so
there would be more energy at a given distance in the "gain" direction than inverse-square would indicate.
Maybe *much* more!

The extreme of this would be a collimated "beam" such as you'd get from a properly configured dish reflector.
Surely in this case the fall-off of intensity would be purely the "loss" aspect of the medium it's passing
through, which would be linear with distance, and may not be significant?  In this case the inverse-square law
would be misleading to the point of being dangerous - if the loss in air isn't significant, standing in or
passing through the "beam" you would encounter almost all of the energy being transmitted, with little regard
to distance.

Or have I just had too much coffee this morning?  :-)

Cheers,


Howard Winter
St.Albans, England

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2004\08\06@074349 by Howard Winter

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Russell,

On Fri, 6 Aug 2004 15:55:41 +1200, Russell McMahon wrote:

>...<
> Prudent avoidance.
> Practice prudent avoidance.

I've always tried to avoid Prudence - she's a nasty, vicious girl!  :-)

>...<

> the brighter the plant colour the better it is for you (usually)

Never heard this one - what about Foxglove (Digitalis) - that's pretty bright and not good except as a
medicine...

> practice moderation in everything - but do so with moderation

I think some people take moderation to extremes... :-)


> avoid badly burned food

Also avoid undercooked food!

> don't sniff PICs (except in BGA or similar leadless packages)

You're doing a Douglas Adams on us here, aren't you?  :-)

> consider not living in congested / smoggy cities (but remember what happened at Lockerbie)

Very sad that - living in a nice quiet village miles from anywhere, and someone drops a 747 on your house.
Rather supports the tenet: "Live for today", doesn't it?

> fill in the intentions book in every hut

This must be a Kiwi-thing - I think I know what it means but perhaps a short explanation, please?

> emergency satellite locator beacons are cheap to hire

Not in the UK they're not!  Emergency equipment always looks expensive for what you get, unfortunately, so
people still fly across the Channel in light aircraft with no liferaft, just lifejackets, whose main task in
this situation is to make it easier to find the body :-(

> excess alcohol and boating is a fatal mix

*Any* alcohol and flying is (if I can say this) even more so!  If you find you are incapable of sailing for
any reason you can just sit there and wait.  That option is not available if you're the pilot of an aircraft!

> This could be quite a fun list when complete.

Indeed, and you may be able to get it made into a poster, sell millions, and become a Very Rich Man.  Which is
probably bad for you...  ;-)

Cheers,


Howard Winter
St.Albans, England

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2004\08\06@074557 by Howard Winter

face
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Russell,

On Fri, 6 Aug 2004 21:18:50 +1200, Russell McMahon wrote:

> Ginkgo Biloba I'm not yet convinced about :-(

I'd always assumed this was some little herb-like plant, until I was on a bus-tour of Washington DC and they
pointed them out, planted along the streets (of Georgetown, I think) - they're stonking great trees!  :-)

Cheers,

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2004\08\06@080012 by John Ferrell

face picon face
A loong time ago I was measuring the output frequency of a 25 Watt
Navigation beacon transmitter (about 300khz) with a hand held counter at the
antenna when it arced over to the meter and then my hand . The arc entered
between my thumb & finger leaving a small cauterized hole It felt like a
needle had been inserted there and all the way up my arm. It took forever to
heal the entry wound. It smelled like burning flesh.

I have never been curious again about how bad a shock might be. I just don't
do it.

John Ferrell
http://DixieNC.US

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To: <TakeThisOuTPICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Thursday, August 05, 2004 11:04 PM
Subject: Re: [OT:] Microwave ovens was WIFI Waveguide antenna

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2004\08\06@080636 by Russell McMahon

face
flavicon
face
> > While we do know that radiation intensity decreases as a square function
with respect to distance

> BUT!  What if the radiator isn't isotrpoic, but has "gain" in a particular
direction?  Surely the whole point
> of a gain antenna is to increase the energy in the wanted direction at the
expense of the other directions, so
> there would be more energy at a given distance in the "gain" direction
than inverse-square would indicate.
> Maybe *much* more!

If the radiator takes a spherical distribution and concentrates it into a
spherical segment with surface area an Nth of a sphere at a given radius
then you still get inverse square law but with a constant factor of N
stronger at a given distance. Classical gain antenna.

If you can manage to collimate the wavefront so that it is as parallel as
possible then you get something closer to what you are suggesting and
non-inverse-square dissipation.

One example of a strangely behaved waves are "Solitons" which have a decay
characteristic that causes them to reinforce themselves as they travel.
Early known examples occurred in English barge canals where occasional large
isolated waves were observed to travel at about fast horse back speed for
many miles with minimal loss of shape or amplitude. Doesn't break the laws
of physics - just explores them.

It seems intuitive (even if not correct :-) ) that waves / particles exhibit
Soliton behaviour.
Haven't Googled on solitons for some years but I'm sure there will be heaps
thereon.

Googles ...

182,000 hits.

Here they are attempting to recreate the original 1834 observation

       http://www.ma.hw.ac.uk/solitons/press.html

What say i stop there before another hour is blown :-)



       RM

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2004\08\06@081711 by Russell McMahon

face
flavicon
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> consider not living in congested / smoggy cities (but remember what
happened at Lockerbie)

Very sad that - living in a nice quiet village miles from anywhere, and
someone drops a 747 on your house.
Rather supports the tenet: "Live for today", doesn't it?


I visited Lockerbie especially on our round-the-world trip. There are no
signs or notices. There is a large memorial at the town entrance but 99+% of
people who see it would not recognise it as such. That is intentional. They
go out of their way to make the cemetery inobvious to tourists. I can
understand and appreciate that. We were too awed to ask anyone for
directions. We found the cemetery in due course, out beyond the town. A most
awe inspiring and moving and saddening and uplifting experience. Maybe 10 or
so people there when I visited. I took my usual photos of the memorial
gardens etc BUT I was very very circumspect with the camera and felt more
like an intruder there than almost anywhere else I went.

> > fill in the intentions book in every hut
>
> This must be a Kiwi-thing - I think I know what it means but perhaps a
short explanation, please?

"Back country" huts have books where you record where you are intending to
go, how long you intend to be, where you plan to exit. Makes it easier to
find your body, as you say.

> > emergency satellite locator beacons are cheap to hire

> Not in the UK they're not!  Emergency equipment always looks expensive for
what you get, unfortunately, so
> people still fly across the Channel in light aircraft with no liferaft,
just lifejackets, whose main task in
> this situation is to make it easier to find the body :-(

Dirt cheap to hire in NZ. Just a few minths ago we had an Englishman doing a
substantial South island solo traverse. Said that locator beacons weighed
too much. had a fall. Was found dead about a month after reported overdue.
In his sleeping bag. had fallen and had sustained a broken something or
other. Obviously had been too damaged to proceed. Would quite possibly have
lived if he's had a locator beacon. Sad.



       RM

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2004\08\06@082747 by Jinx

face picon face
> > emergency satellite locator beacons are cheap to hire
>
> > Not in the UK they're not!

Most common phrase in friends e-mail during UK winter -

"another bunch of wallies lost on Snowdon"

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2004\08\06@083126 by Alan B. Pearce

face picon face
>One example of a strangely behaved waves are "Solitons"
>which have a decay characteristic that causes them to
>reinforce themselves as they travel. Early known examples
>occurred in English barge canals where occasional large
>isolated waves were observed to travel at about fast
>horse back speed for many miles with minimal loss of shape
>or amplitude. Doesn't break the laws of physics -
>just explores them.

Oh, you mean like the tidal surge up the Severn River. People can ride a
surfboard for several miles upriver on it.

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2004\08\06@084204 by Jinx

face picon face
> Green tea can't hurt (I hope :-) ).

I faxed this to someone just the other day

http://smh.com.au/articles/2004/07/27/1090693968292.html?oneclick=true

Plenty of praise for green tea on the web

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'[OT:] WIFI Warning'
2004\08\06@100153 by Herbert Graf

flavicon
face
On Fri, 2004-08-06 at 06:16, Russell McMahon wrote:
> > > >Can you suggest a starting point for me to learn
> > about WiFi security?
> > >
> > > There's not a lot to it.
> > > Turn encryption on, change keys as often as practical.
> >
> > There's also: Choose as high a number of bits for the
> > encryption key that you can.  As I understand it, it's a
> > geometric progression - 128 bits isn't twice as hard as
> > 64, it's 64 times as hard.
>
>
> Probably ~~ 2^64 times as hard.
>
> 64 bits can be cracked in hours using eg ?Net Stumbler.
> Last time I read up on this (over a year ago) 128 bits was theoretically
> crackable but in practice was believed to be essentially secure to all but
> perhaps the experts with a serious grudge and very serious computing power.
> Has this changed since then?

Yes. While you are correct with a brute force attack against 128 bit
encryption a brute force attack is rarely used to break into things.

With WiFi there is a design flaw in the way encryption is done,
basically there are certain combinations of packets that are easier to
crack then others, so to break into a WEP based WiFi connection you just
have to sit there sniffing packets until you see enough of the
"interesting" ones, once you have enough you start a brute force type
attack on that small subset, which doesn't take very long at all. Most
of your time is spent waiting for the interesting packets.

This is often how encryption is broken BTW, even Enigma was broken in a
kinda similar way (they had an idea of what was being sent and could
chug away combinations until the result made sense).

Moral of the story? WEP is good for keeping someone out for a short
while, but anybody with time can break it with little effort.

The new encryption standard for WiFi (WPA) fixes these flaws (along with
other flaws) and is far more secure. TTYL

TTYL

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\06@101851 by Russell McMahon

face
flavicon
face
> Most common phrase in friends e-mail during UK winter -
>
> "another bunch of wallies lost on Snowdon"

How could you get lost on Snowdon?
From what I could see you walked up to get up and down to get down.
Maybe I missed something :-)
(I was only looking from the high point on the road.)


       RM

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2004\08\06@104108 by David VanHorn

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>
>BUT!  What if the radiator isn't isotrpoic, but has "gain" in a particular direction?

Inverse square still holds, because the area painted will still be proportional to the square of the radius.

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2004\08\06@125527 by Robert Rolf

picon face
Howard Winter wrote:
{Quote hidden}

The show was actually quite hilarious as they tried many different
ways to get their life sized dummy to pee correctly. Used a balloon
filled with saline emptying through a small hose. Windshield washer
pump and reservoir, etc. In each case the stream broke into
drops about 18" out so they finally had the dummy kneeling over the
simulated 3rd rail draining straight down to get the conductive
circuit.

dsc.discovery.com/fansites/mythbusters/mythbusters.html
http://dsc.discovery.com/fansites/mythbusters/episode/episode.html

Episode 3: Barrel of Bricks, Pissing on the Third Rail, Eel Skin Wallet

Is it really that dangerous to answer the call of nature on the
electrified third rail of a train track? Can an eel skin wallet erase
all the magnetic information on your credit cards if the skin came from
an electric eel? How about the story of the unluckiest construction
worker on earth? A pulley system breaks down while he is lifting a
barrel filled with 500 pounds of bricks. Will the barrel come straight
down on the guy doing the pulling, or will he walk away without a
scratch? Jamie and Adam take a crack at these classic legends.

Now if you are peeing on the fence from 6" away, at waist height,
you may well get a memorable experience.

Now if I could only electrify the big rock at our property line
that the local dogs have to 'mark', without getting caught <G>.

Robert

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2004\08\06@125943 by David VanHorn

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> Can an eel skin wallet erase all the magnetic information on your credit cards if the skin came from an electric eel?

Not exactly.

Eel skin wallets did cause a major upheval in the credit card industry.
Of course the problem was not the Eel skin itself, but the MAGNETIC closures they used.

Just call me an expert witness on this one.

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'[OT:] WIFI Warning'
2004\08\06@131153 by Nate Duehr

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On Aug 6, 2004, at 4:01 AM, Howard Winter wrote:
> As a matter of interest, what software did you use?  The
> stuff I've seen wouldn't record this for you over a
> session, just show you it "live".  I presume you weren't
> operating it yourself while driving!  :-)

Definitely not operating while driving (other than an occasional
glance).  Know better than to do that -- too many years of mobile
DF'ing and knowing what happens to people who don't bring along a
helper when doing that.  (They end up in the ditch on a dirt road
somewhere.)

Was using NetStumbler.  http://www.netstumbler.com/downloads/

Audible alerts when in/out of range of an AP, will hook up to a GPS if
desired and track locations where different AP's heard, has it's own
proprietary log file output or you can export to a number of other
formats... etc.

It's been around a long time.  Does have limitations on what cards it
will work with, read the Release Notes.

Their MiniStumbler for PocketPC devices is pretty nifty too.  Good
security tool for network admins to go hunting for unauthorized WiFi
AP's inside their buildings/on their networks.

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2004\08\06@132458 by David VanHorn

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At 12:09 PM 8/6/2004, Nate Duehr wrote:

>On Aug 6, 2004, at 4:01 AM, Howard Winter wrote:
>>As a matter of interest, what software did you use?  The
>>stuff I've seen wouldn't record this for you over a
>>session, just show you it "live".  I presume you weren't
>>operating it yourself while driving!  :-)
>
>Definitely not operating while driving (other than an occasional
>glance).  Know better than to do that -- too many years of mobile
>DF'ing and knowing what happens to people who don't bring along a
>helper when doing that.  (They end up in the ditch on a dirt road
>somewhere.)
>
>Was using NetStumbler.  http://www.netstumbler.com/downloads/


I found a couple screenfuls of unsecured APs here in Muncie, the technological armpit of farm country.  I can only imagine what it must be like in tech-friendly areas.

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2004\08\06@184922 by Howard Winter

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On Fri, 6 Aug 2004 12:24:23 -0500, David VanHorn wrote:

> At 12:09 PM 8/6/2004, Nate Duehr wrote:
>
>...<
> >Was using NetStumbler.
http://www.netstumbler.com/downloads/
>
> I found a couple screenfuls of unsecured APs here in
Muncie, the technological armpit of farm country.  I can
only imagine what it must be like in tech-friendly
areas.

Well I just downloaded it and went for a quick drive of
a couple of miles around what is basically a village,
and got 13 hits, only 3 of which were using encryption,
and 8 of which were using the default SSID for their
Access Point (Linksys, Netgear, belkin54g, etc) so the
odds are they haven't changed the admin password either!
:-)

Interesting choice of channels, too - only six different
between them, with 6 and 11 being particularly popular.

Thanks for the pointer, Nate!

Cheers,

Howard Winter
St.Albans, England

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2004\08\06@185455 by David VanHorn

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>
>Well I just downloaded it and went for a quick drive of
>a couple of miles around what is basically a village,
>and got 13 hits, only 3 of which were using encryption,
>and 8 of which were using the default SSID for their
>Access Point (Linksys, Netgear, belkin54g, etc) so the
>odds are they haven't changed the admin password either!
>:-)

Makes you wonder why anyone pays for wireless internet, doesn't it?

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\06@185703 by Russell McMahon

face
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> >BUT!  What if the radiator isn't isotrpoic, but has "gain" in a
particular direction?
>
> Inverse square still holds, because the area painted will still be
proportional to the square of the radius.

This assumes (As I noted) that the radiation is effectively just confined to
a spherical subset and is effectively a point source at point of origin. If
the radiator is a non point source that collimates the wave IMO you get non
inverse-square results. Examples might be phased array type systems.

B, IMBW :-)  (as Carl Sagan was fond of saying).



           Russell McMahon

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2004\08\06@190530 by David VanHorn

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At 05:56 PM 8/6/2004, Russell McMahon wrote:

>> >BUT!  What if the radiator isn't isotrpoic, but has "gain" in a
>particular direction?
>>
>> Inverse square still holds, because the area painted will still be
>proportional to the square of the radius.
>
>This assumes (As I noted) that the radiation is effectively just confined to
>a spherical subset and is effectively a point source at point of origin. If
>the radiator is a non point source that collimates the wave IMO you get non
>inverse-square results. Examples might be phased array type systems.

Not too likely in the case of the dropped microwave oven.

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2004\08\06@203328 by Russell McMahon

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> Not too likely in the case of the dropped microwave oven.

Agree.
The person who suggested this was making a more general case AFAIR.

       RM

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2004\08\06@205233 by Rich

picon face
True: The inverse square relation still holds.

----- Original Message -----
From: "David VanHorn" <KILLspamdvanhornspamTakeThisOuTCEDAR.NET>
To: <TakeThisOuTPICLISTspamspam_OUTMITVMA.MIT.EDU>
Sent: Friday, August 06, 2004 7:06 PM
Subject: Re: [OT:] Microwave ovens was WIFI Waveguide antenna


> At 05:56 PM 8/6/2004, Russell McMahon wrote:
>
> >> >BUT!  What if the radiator isn't isotrpoic, but has "gain" in a
> >particular direction?
> >>
> >> Inverse square still holds, because the area painted will still be
> >proportional to the square of the radius.
> >
> >This assumes (As I noted) that the radiation is effectively just confined
to
> >a spherical subset and is effectively a point source at point of origin.
If
> >the radiator is a non point source that collimates the wave IMO you get
non
> >inverse-square results. Examples might be phased array type systems.
>
> Not too likely in the case of the dropped microwave oven.
>
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'[OT:] WIFI Warning'
2004\08\06@212554 by Josh Koffman

face picon face
There are a couple reasons for that. First, most people have no idea
what the channel setting means, so they don't touch it. Second, the
way things are laid out in the band is kind of screwy. There are only
3 non overlapping channels I believe, so some of the products I've
seen will only let you select one of the three.

Josh
--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
       -Douglas Adams

On Fri, 6 Aug 2004 23:49:17 +0100, Howard Winter <RemoveMEhdrwspamspamSTOPspamh2org.demon.co.uk> wrote:
> Interesting choice of channels, too - only six different
> between them, with 6 and 11 being particularly popular.

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2004\08\07@104446 by Gerhard Fiedler

picon face
>> Can you suggest a starting point for me to learn about WiFi security?
>>
>> I'm thinking seriously about getting a WiFi rig for use at home before
>> trying to deploy a system for here at work.  Security is one of my main
>> concerns and I'm not comfortable with installing a wireless network at
>> work
>> until I have learned enough to secure it.

> At the very least:  Use WPA (newer version of WEP with rotating keys,
> and other fun) and turning off "Beaconing" on your Access Point is
> probably "relatively" secure for a home network.   Keep up with your AP
> vendor's latest firmware releases if they have any.  Those two will
> generally keep anyone casually sniffing for wireless networks away.
>
> Other techniques that work well ...

I've seen some AP/router combinations that allow restricting connections to
a selection of MACs. I'm not sure whether this applies also to pure APs.

Gerhard

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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\07@111841 by Peter L. Peres

picon face
>Also, a special parabolic antenna design can focus the uWave at a
>specific (x,y,z) point.  The energy can also be made to concentrate at
>that point. These techniques are also used in optics.  You can get
>seriously hurt by attempting experiments you are not ready for.

And you do not need a microwave oven for that, the sun is plenty enough.

Peter

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'[OT:] WIFI Warning'
2004\08\07@183642 by William Chops Westfield

face picon face
On Aug 7, 2004, at 7:44 AM, Gerhard Fiedler wrote:

> I've seen some AP/router combinations that allow restricting
> connections to
> a selection of MACs. I'm not sure whether this applies also to pure
> APs.
>
Oooh.  Like MAC addresses are SO secure!

BillW

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2004\08\07@185754 by M. Adam Davis

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Dwayne Reid wrote:

> Can you suggest a starting point for me to learn about WiFi security?
>
Treat your wireless link as if the data that goes across it goes across
the wide open internet.  Securing it is as simple as securing the
internet connection coming into your building, and all your wireless
clients are on the other end of the internet.  A robust VPN solution is
about as good as it gets.

However, consider the cost/performance ratio.  I use a simple 128bit WEP
key for my private home network.  It's not something I'm going to spend
too much time protecting since there are so many other targets out
there.  A hacker will go to an open connection long before they'll
settle down and attack me, unless they are specifically targetting me,
which I don't believe is a very likely thing.  Futher, I've placed my
access point in the basement, so it basically goes up into the house,
and doesn't get good signal outside of the home (aluminum siding).

My ADSL modem is the router and AP, so securing it is harder since I
cannot change the operation of the router, or seperate the AP from the
router and from the internet connection.  Otherwise I might consider
another layer of protection (VPN with a rate limited tunnel for public
internet access).  But it's another piece of equipment to secure, and an
option I'm not going to take right now since it would require disabling
my current AP and adding a seperate one.

But that's the best advice I can give on securing a wireless connection
- pretend that your data passes directly through your worst enemy's
computer between the AP and the client.

-Adam

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2004\08\09@051645 by Nate Duehr

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Gerhard Fiedler wrote:

> I've seen some AP/router combinations that allow restricting connections to
> a selection of MACs. I'm not sure whether this applies also to pure APs.

True, but if you've either been reading unencrypted packets between a
node and the AP or you've cracked their WEP, you can then easily spoof
their MAC address, and gain full access to their network.  It's not
difficult to change MAC addresses these days, most cards will let you
override their manufacturer's default MAC in software.

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2004\08\09@071915 by Anthony Toft

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> True, but if you've either been reading unencrypted packets between a
> node and the AP or you've cracked their WEP, you can then easily spoof

Seconding this statement...

Regardless of WEP encryption, the MAC address is clear text. MAC address
limiting _IS NOT_ a form of security, it is not even a reasonable
identification method.

The two facets of security, "access restriction" and "data privacy" are
not adequately addressed by WEP, as is evidenced by the amount of
software freely available to crack it.

The only way to truly secure wireless is to step up to IPSec and use
public/private key encryption (for at least part of the packet, the rest
is symmetrical) with a VLAN router having strict rules not to forward
pure wireless traffic. Even then you are only stopping access from an
unknown on wireless to your services (including internet services) you
will not stop 2 unknown people from talking to each other using your AP.
So you are still vulnerable to (varying levels of) DOS attacks

We have been dealing with this at work as we are trying to connect an
insecure Wireless network to the corporate LAN.

Anthony
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'[OT:] Microwave ovens was WIFI Waveguide antenna'
2004\08\11@075149 by Jinx

face picon face
> be forewarned that in older ovens without carousels, water in
> a container sitting very still can become superheated in a
> microwave oven.  Upon disruption by some object (thermometer
> in this case) the superheated (above boiling point but not
> boiling) water can and will explode out of the container as it all
> instantaneously boils over, flashing to steam and covering the
> unsuspecting "scientist" with boiling water

Located my video of this today (it's tiny - 65kB)

http://home.clear.net.nz/pages/joecolquitt/hotstuff.html

(I noticed the date I made this was 13/4/01 - getting old too quick)

The man with the beaker said it felt "not uncomfortably hot". Then
he dropped the coffee in - and whoosh

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'[OT:] WIFI Waveguide antenna'
2004\08\12@015616 by Robert B.

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Hello everybody,

I finally got around to building one of the USB-dongle style antennas, and
let me say WOW it blows away my tin-can waveguide antenna.  The s/n ratio is
much better, and dropped packets are almost non-existant.  The windows icon
thingy went from "Very low" to "Very Good", and the netstumbler readings
increased dramatically, from about -85dB to -60dB.

The basic design utilized a $2.95 wire strainer from my local Wally-world,
along with a linksys Wireless-B (I skimped) USB Network adapter (model
WUSB11).  A little hot glue and a tripod completed the rig.  It's no longer
necessary to string the cable into the next room for acceptable reception,
and from what I can tell the reception is improved dramatically over the
previous design.  I'm even picking up a few other networks in the
neighborhood.

The new antenna is somewhat directional, but picks up an acceptable signal
for about 100 degrees of rotation.  This indicates that perhaps the antenna
is not at the reflectual center of the wire strainer, or the strainer is not
truly parabolic (or both..).  But at any rate I can't complain.  The USB
connection installed easily as well.

Picture of the rig here:  http://www.nerdulator.net/files/wifi.jpg


{Original Message removed}

2004\08\12@194621 by John Ferrell

face picon face
You done good!
Just remember, if you see them, they can see you...

John Ferrell
http://DixieNC.US

{Original Message removed}

'[OT:] WIFI Ethics?'
2004\08\12@200907 by Robert B.

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face
That worries me a little.. I hope I'm not breaking any laws up here!  When
the antenna is aimed at my router, another neighborhood signal is also
available.  If for some reason my router were to stop broadcasting, the
other signal would become the strongest one, and Windows would probably try
to log me onto that network!  No doubt that would break more than a few
laws.


{Original Message removed}

2004\08\12@201942 by Jason S

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face
Does windows automatically log you on?  I've only used WiFi on a Mac, but it
prompts you the first time it sees a network and asks if you want to
connect.

I don't think there is any legal issue with accessing an unsecured access
point.  If you're breaking encryption to get in, it's a different story.  As
far as I know, the laws don't cover open points, but I'm not a lawyer :)

Jason

{Original Message removed}

2004\08\12@203433 by Andrew Warren

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Jason S <RemoveMEPICLISTRemoveMEspamRemoveMEmitvma.mit.edu> wrote:

> I don't think there is any legal issue with accessing an unsecured
> access point.  If you're breaking encryption to get in, it's a
> different story.  As far as I know, the laws don't cover open
> points, but I'm not a lawyer :)

   If I leave the front door to my house unlocked and you walk in
   without my permission, you might not be guilty of breaking and
   entering, but you're certainly trespassing.

   -Andrew

=== Andrew Warren -- aiwKILLspamspamspamcypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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2004\08\12@203847 by Robert B.

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But what if your front door intrudes onto my property?

----- Original Message -----
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Sent: Thursday, August 12, 2004 8:38 PM
Subject: Re: [OT:] WIFI Ethics?


{Quote hidden}

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2004\08\12@210001 by Jason S

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From: "Andrew Warren" <STOPspamaiwspam_OUTspamspamBeGoneCYPRESS.COM>
Sent: Thursday, August 12, 2004 5:38 PM

That's exactly the example I kept coming up with.  If the door is closed
even unlocked, it is still breaking and entering.  If the door is open it is
not.  It would probably be trespassing, but without no trespassing signs,
I'm not sure even that would be illegal.  I can use your driveway to turn my
car around without breaking any laws.

If I enter your house through an open front door and leave as soon as you
ask me to, I don't think I've broken any laws.

In any case, the analogy is not perfect.  To trespass, I need to physically
be on your property.  The same is not true to access your wireless router.
If anything, you're trespassing on my property by putting your radio waves
on my property :).

Jason

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2004\08\13@112639 by Win Wiencke

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<Snip>
>  If the door is closed
> even unlocked, it is still breaking and entering.  If the door is open it
is
> not.  It would probably be trespassing, but without no trespassing signs,
> I'm not sure even that would be illegal.

<Snip>
> To trespass, I need to physically
> be on your property.  The same is not true to access your wireless router.
> If anything, you're trespassing on my property by putting your radio waves
> on my property :).

Using the other person's bandwidth is a "taking" of the property of another.
It is theft not trespass.

Win Wiencke
Image Logic Corporation

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2004\08\13@143847 by Gerhard Fiedler

picon face
> In any case, the analogy is not perfect.  To trespass, I need to physically
> be on your property.  The same is not true to access your wireless router.
> If anything, you're trespassing on my property by putting your radio waves
> on my property :).

Ever seen those welcome messages when you log in to a server that basically
say that if you're not authorized you should please leave immediately?

Of course they don't do anything against a hacker :)  But they are probably
the equivalent to a "no trespassing" sign. Without even marking your
territory, you probably can't expect that others know how to honor it.

Gerhard

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2004\08\13@160259 by Jason S

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From: "Win Wiencke" <RemoveMEWinTakeThisOuTspamSLYCURVES.COM>
Sent: Friday, August 13, 2004 8:26 AM

> Using the other person's bandwidth is a "taking" of the property of
another.
> It is theft not trespass.

Where in the legal code is bandwidth defined as property?

To introduce an analogy once again, if you leave the garden hose running on
your driveway and someone comes up at takes a drink from it, have they
stolen water from you?

Jason

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2004\08\13@163656 by Steve Willoughby

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On Fri, 13 Aug 2004, Jason S wrote:
> Where in the legal code is bandwidth defined as property?

Depends on where you live.  Many states in the USA are adopting
computer crime laws which make it a felony to alter a computer
without permission or to interfere with its operation.  Using
bandwidth could be considered a denial of service attack if
you're degrading their performance.  If, on top of that, you
gained access to their own computers or did something inappropriate
on the net using their connection (making it look like they were
the source of the spam/hack/whatever), that would be a much more
likely indictment, but even so... these are largely untested,
unproven legal waters with little in the way of precedent.

I'd err on the side of caution on this one and not use any network
which isn't made explicitly public or licensed for your use.

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2004\08\13@170353 by Jason S

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I knew I'd read about this issue recently.  The Priority Interrupt column in
the July 2004 Circuit Cellar talks about it.  This is the only discussion
group I access where I can expect a decent percentage of the people to have
access to that magazine :).

As you say, it is unproven legal waters.  The law does have a requirment for
you to intend to do whatever was illegal to actually be guilty (whether or
not you knew your actions were illegal, they had to be deliberate actions).
So the original poster who was worried that if his router went down, he'd
automatically connect to the other router without knowing should be safe.

The other issue we're talking about is a lot more diffucult.  I would argue
that using bandwidth is not a denial of service attack if your intention is
not to deny service and you don't try to consume all the person's bandwidth.
Most of the time, most of the bandwidth is going unused anyway.  With
cablemodems your bandwidth is shared among all the people on your subnet.
If a few people download a big file, it will slow everyone else's
connections.  Are they engaged in a denial of service attack?

Spam/hack/whatever is illegal so then you are committing a computer crime,
and if you make it look like the owner is guilty, that's also impersonation.
None of that makes accessing the network itself illegal.  Same issue if you
gain access to his own computers.  Presumably, that would require defeating
protective measures which is illegal.  Accessing an unsecured router doesn't
requre defeating protective measures.

I access free WiFi spots all the time (at the public library, several
restauarants and cafes that offer it, etc).  It seems like leaving access
open should be considered an invitation, even a personal router.

Jason


From: "Steve Willoughby" <steve.....spam@spam@ALCHEMY.COM>
Sent: Friday, August 13, 2004 1:28 PM

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2004\08\13@172048 by 4HAZ

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----- From: "Jason S" <pic@
<snip>
> I access free WiFi spots all the time (at the public library, several
> restauarants and cafes that offer it, etc).  It seems like leaving access
> open should be considered an invitation, even a personal router.
>
> Jason

We are in the process of setting up a large scale broadband network,
with canopy gear for backhaul 40MB/s (2 20MB/s units on a dual dish)
and WiFi access points.
At present the system is wide open for ease of testing, and there is quite a
lot of activity on it, many people are getting a free-ride for now.
We hope they will become our first subscribers when the system is fully
in-place and free from outages (outages are common during the building
stage)

KF4HAZ - Lonnie

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2004\08\13@174542 by Win Wiencke

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> > Using the other person's bandwidth is a "taking" of the property of
> another.
> > It is theft not trespass.
>
> Where in the legal code is bandwidth defined as property?

In a Capitalist system the underlying notion of property law is that things
of value have owners.  Instead of cataloging which things are property and
which are not, the legal code takes great pains to describe what constitutes
ownership.  The legal code also describes how the State will help protect
this right of ownership -- without which the whole Capitalist system would
collapse.

Thus, a transaction (sale or lease) can legally define ownership as well as
property because it simultaneously demonstrates that the goods or service
has a value (becomes property) and documents who the owner is.

One such transaction is purchasing or leasing a car. You give your money in
exchange for ownership rights to the car.  The value of the money
establishes that the car or use of the car has value -- it becomes
"property.".  The receipt for the money establishes that you are the owner
of the car or use of the car.  Should someone take the car, the legal code
describes how the State will assist you in asserting your ownership rights.

Another such transaction is the monthly payment to your ISP for a connection
to the Internet.  Here again the transaction establishes both property and
ownership.

Under English law imprudently forgetting to remove the keys from one's car
does not automatically transfer ownership of the car to whomever hops in and
drives off.  Similarly, using a wireless connection imprudently does not
automatically transfer the use and enjoyment of the bandwith.

Incidentally, the notion of "trespass" has roots in property law.  Under
English law a land owner is intitled to the "fruits of the property" and one
right of ownership is the presumption that only the owner has the right to
determine who may harvest, or hunt on the property.

The person who walks up your driveway to take a drink of water from your
running hose is a trivial example of trespass and theft.  It would not be
trivial if they put the hose down and the water took a different route --
and flooded your basement.

But I rant....

Win Wiencke
Image Logic Corporation

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2004\08\13@181244 by Jason S

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The legal system makes very important distinctions.  For example,
downloading music from a p2p network and burning it to CD is not theft, no
matter how much the RIAA might say it is.  It's illegal (though not in
Canada), but the crime is copyright infringment.  Nothing has been stolen.
Even if you mass produce copies of the song and sell them for profit, it is
not theft.

Great example with the car.  If you leave it parked somewhere, and somebody
uses the bumper as a footrest to tie their shoe, is that a crime?  Now if
that same person picks the lock (being careful to not even scratch the
paint), opens the door, and uses the front seat as a footrest to tie their
shoe, is that a crime?

If someone puts the hose in your basement, their crime is still not taking
the water.

In order for something to have legal protection, you must take measures to
protect it.  The DMCA is one of the most draconian pieces of legislation
ever written (well, before the patriot act anyway), and even it requires
that there be some sort of protection that is circumvented before a crime is
committed.

What if I open a private radio station and broadcast normally but every 5
minutes say "this service is not free, if you are listening without paying
$5/month, you are stealing this signal".  Is it theft or any sort of crime
to listen anyway?

Jason

From: "Win Wiencke" <WinspamspamTakeThisOuTSLYCURVES.COM>
Sent: Friday, August 13, 2004 2:45 PM


> In a Capitalist system the underlying notion of property law is that
things
> of value have owners.  Instead of cataloging which things are property and
> which are not, the legal code takes great pains to describe what
constitutes
> ownership.  The legal code also describes how the State will help protect
> this right of ownership -- without which the whole Capitalist system would
> collapse.
>
> Thus, a transaction (sale or lease) can legally define ownership as well
as
> property because it simultaneously demonstrates that the goods or service
> has a value (becomes property) and documents who the owner is.
>
> One such transaction is purchasing or leasing a car. You give your money
in
> exchange for ownership rights to the car.  The value of the money
> establishes that the car or use of the car has value -- it becomes
> "property.".  The receipt for the money establishes that you are the owner
> of the car or use of the car.  Should someone take the car, the legal code
> describes how the State will assist you in asserting your ownership
rights.
>
> Another such transaction is the monthly payment to your ISP for a
connection
> to the Internet.  Here again the transaction establishes both property and
> ownership.
>
> Under English law imprudently forgetting to remove the keys from one's car
> does not automatically transfer ownership of the car to whomever hops in
and
> drives off.  Similarly, using a wireless connection imprudently does not
> automatically transfer the use and enjoyment of the bandwith.
>
> Incidentally, the notion of "trespass" has roots in property law.  Under
> English law a land owner is intitled to the "fruits of the property" and
one
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2004\08\13@202800 by Win Wiencke

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> The legal system makes very important distinctions.  For example,
> downloading music from a p2p network and burning it to CD is not theft, no
> matter how much the RIAA might say it is.  It's illegal (though not in
> Canada), but the crime is copyright infringment.  Nothing has been stolen.
> Even if you mass produce copies of the song and sell them for profit, it
is
> not theft.

In the US this would be a novel interpretation to say the least.

Check out Article 1, Section 8 of the US Constitution "...securing for
limited times to authors and inventors the exclusive right to their
respective writings and discoveries."  This is an enumerated right of
ownership.  "Exclusive" means that only the  author or inventor may withhold
or give away this right as they see fit -- not me, not you, not the
downloader, not the government, not my Aunt Fanny.

Your reductum ad absurdum logic is artfully wielded and worthy of a skillful
engineer.  Alas, the affairs of people rarely follow logic.

That's why there is the idea of "law" and "equity."  The "law" is the
rules - rigid and unyielding as blind justice's scales.  "Equity" is what's
fair and holy.  Like the King and the Church they evolved from, these two
butt heads quite regularly in the courtroom.

I don't have a right to use your car as a footrest even if it is left
unprotected and in the open.  But you'd look awfully silly taking me to
court when you can demonstrate only that I did not first ask your
permission.  The question of "equity" would kick in and you'd be asked how
you were harmed.  Not having any demonstrable damages doesn't change the law
it just illustrates why people, not adding machines, have to administer the
law.

I don't have the right to take a key and scratch the finish of your car even
if it is left unprotected in the open.  Perhaps I could argue that you had
no sign to the contrary and that the car had so many scratches that my
artistry could only improve it, but as the owner you have the exclusive
right to determine the appearance of your car.  There might be a
considerable wrangle over the extent my liability, but no question about
your legal right as owner.  Equity would clearly take a backseat to law in
this instance.  I would have taken your ownership right to determine the
appearance of your car.

Were I to open your car door and use the seat as a foot rest I am adding an
aggravating factor and evidence that my action is intentional and
deliberate.  You might argue that you have a reasonable expectation that
passers-by will not enter your car for any purpose.  You might argue that
although I caused no damage I took from you a sense of security and
exclusivity.  Any equity argument I might have would be quite suspect.  I
took from you something that you clearly value and which you protected with
your investment in a lock and door.

If you doubt the logic behind the legal underpinnings for that sort of
"taking," just ask any woman how she'd feel if someone entered her boudoir,
opened her drawer, sniffed her lingerie, neatly replaced everything and
left.  Was nothing of value taken?

When I was a student my folk's telephone was a party line.  I would call
home from abroad and click by click the volume would diminish as neighbors
listened in to be first with the latest gossip.  We didn't mind; but if we
did, was nothing of value taken?

Telemarketers and SPAM consume bandwidth.  The effect is to raise the cost
for communications, load on the infrastructure, and squander the electricity
to manage the bandwidth -- not to mention the time recipients are forced to
spend.

You bet something of value is taken when someone steals bandwidth.

After this rant, you deserve the last word <g>

Win Wiencke
Image Logic Corporation

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2004\08\14@062658 by Howard Winter

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Win,

On Fri, 13 Aug 2004 11:26:47 -0400, Win Wiencke wrote:

> Using the other person's bandwidth is a "taking" of the property of another.
> It is theft not trespass.

Well it certainly isn't trespass, and under English Law theft is "removing property from the posession of the
owner, with intent to permanently deprive them of it".  I don't believe "bandwidth" can be described as
property, and unless the owner was trying to use all of the available bandwidth at the moment the intruder was
using it, then I don't believe it can be said to have been removed either, so I don't think theft would be
proved.  The only thing is if the owner's equipment uses more electricity while the intruder is active
(unlikely, I think) in which case the intruder can be said to have stolen the electricity.

It is certainly contrary to the Computer Misuse Act though, which covers attempts at unauthorised access to
someone else's system, among other things.

Cheers,



Howard Winter
St.Albans, England

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2004\08\14@063113 by Howard Winter

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On Fri, 13 Aug 2004 13:08:02 -0700, Jason S wrote:

> To introduce an analogy once again, if you leave the garden hose running on your driveway and someone comes
up at takes a drink from it, have they stolen water from you?

Yes, they have permanently deprived you of posession of your property (and I wouldn't ask for it back! :-) so
even though you may have been wasting it, it is yours to waste, not theirs to take.

It's the same if you have a skip full of rubbish outside your house, and someone helps themselves to some of
it.  It's still yours even though you are throwing it away, and if they take it without your permission, they
are stealing.

(Incidentally, there's an ancient law in England that if someone comes to your door and asks for a drink of
water, you have to give it to them - but they have to ask! :-)

Cheers,



Howard Winter
St.Albans, England

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2004\08\14@064736 by Howard Winter

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Win,

On Fri, 13 Aug 2004 20:26:48 -0400, Win Wiencke wrote:

> > The legal system makes very important distinctions.  For example,
> > downloading music from a p2p network and burning it to CD is not theft, no
> > matter how much the RIAA might say it is.  It's illegal (though not in
> > Canada), but the crime is copyright infringment.  Nothing has been stolen.
> > Even if you mass produce copies of the song and sell them for profit, it
> is
> > not theft.
>
> In the US this would be a novel interpretation to say the least.

But in England, it is absolutely true.  You have not removed someone's property from their posession - they
still have the music themselves - so you have not committed theft.  You cannot steal "potential profits" or
any such thing.  The Federation Against Software Theft have used an emotive name to try to get people on their
side, but it is an absolute misnomer.

When people started "joyriding" other peoples' cars, or driving them home after a late night but with no
intention of keeping them, the Theft Act didn't (doesn't) cover it because they were not permanently depriving
the owner of the car,  so a new law "Taking and driving away" had to be enacted to cover it.  However, if they
finish the night with a "Viking burial" of the car, they are depriving the owner of it, so then they have
stolen it.

Cheers,


Howard Winter
St.Albans, England

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2004\08\14@182444 by William Chops Westfield

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On Aug 13, 2004, at 2:45 PM, Win Wiencke wrote:

>> Using the other person's bandwidth is a "taking" of the property of
>> another.
>>
It's more or less the same issues that arose with allowing "guests"
access to the excess CPU cycles on the old timesharing systems.  If no
one else was using the computer, it was just wasteful not to allow
other use of the cycles.  On the other hand, there are so many
POTENTIAL privacy, liability, and abuse issues that not many companies
or even schools were willing to risk it.  I'm pretty sure I don't want
anyone using my wireless and internet connection to upload hate spam
and download kiddie porn, for instance :-(

I'd expect that this is covered by the same laws that occasionally lead
to crackers being charged with 'connecting to the wrong host' (even if
they didn't even log in.)

BillW

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2004\08\14@194319 by Steve Willoughby

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On Sat, 14 Aug 2004, William Chops Westfield wrote:
> It's more or less the same issues that arose with allowing "guests"
> access to the excess CPU cycles on the old timesharing systems.  If no

Yes, but usually we had a guest account that was set up for the purpose
and some control over who got to use it.  I don't recall a typical
system having an open terminal with no password sitting outside the
building for passers-by to use, which is what hijacking someone's
WiFi AP w/o their authorization is more like.

The bigger issue, IMHO is that it's less a matter of what's fair
or reasonable and more a matter of what you can convince a jury
of at the time.

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2004\08\15@174706 by Gerhard Fiedler

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>> To introduce an analogy once again, if you leave the garden hose running
>> on your driveway and someone comes up at takes a drink from it, have
>> they stolen water from you?

> Yes, they have permanently deprived you of posession of your property
> (and I wouldn't ask for it back! :-) so even though you may have been
> wasting it, it is yours to waste, not theirs to take.

But the OP's case is more analog to the situation where someone lets run
water out of his driveway onto the (public) street, and then I fill a
bucket from that stream and wash my car with it. I don't think that there's
something wrong with that, legally or otherwise... :)

Of course it's their loss, but it's their choice to put out a public
carrier that is connected to their (paid and private) internet connection.
It's in a public band, and available to the public. That's the same as if
you were trying to charge somebody with eavesdropping for listening to CB
radio conversations. There could very well be a private conversation going
on, and me listening in could create some financial loss to the ones
talking (like them talking about a stock deal and me taking advantage of
that knowledge), but just because I'm doing something on "public grounds"
that may cause some financial damage to somebody, I'm not yet guilty of
anything.

Gerhard

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2004\08\15@175743 by Gerhard Fiedler

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> It is certainly contrary to the Computer Misuse Act though, which covers
> attempts at unauthorised access to someone else's system, among other
> things.

"attempts": In the OP's case, there were not really any attempts. The
default configuration of a plain vanilla system connects to an available
hot spot. The user isn't even aware of that, unless he's some kind of tech
person, so it can't really be said that he "attempted" it.

"unauthorized access": With so many public hot spots that provide (implied)
authorized access, it is pretty much impossible for a normal user without
special equipment to determine if a hot spot is authorized or not. In the
outside area of an internet café that provides wifi access, most users
don't have a clue whether they are connecting to the café's router or to an
unsuspecting neighbor's router. Is that their fault?

Gaining access by breaking an even weak encryption or hacking an even weak
password is of course a completely different issue.

Gerhard

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2004\08\15@182858 by Russell McMahon

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> But the OP's case is more analog to the situation where someone lets run
> water out of his driveway onto the (public) street, and then I fill a
> bucket from that stream and wash my car with it. I don't think that
there's
> something wrong with that, legally or otherwise... :)

In that case the water has left the private property, and the act of running
over ground has diminished its value. If you replaced water with eg
chocolate coins in metallic paer wrappings, the analogy may be better. ie
they retain their value while running down the hill and the owner MAY decide
to retrieve them. Still not a perfect analogy.

> Of course it's their loss, but it's their choice to put out a public
> carrier that is connected to their (paid and private) internet connection.
> It's in a public band, and available to the public. That's the same as if
> you were trying to charge somebody with eavesdropping for listening to CB
> radio conversations. ...
>....         but just because I'm doing something on "public grounds"
> that may cause some financial damage to somebody, I'm not yet guilty of
> anything.

In my country you may LISTEN legally, but acting on received information is
illegal.

With WIFI, it's one thing to receive the carrier, but as soon as you send
signals through the associated switching system you are doing something
quite recognisably different.

I see the main point of uncertainty in how hard you need to protect against
TRULY ACCIDENTALLY doing something which someone else, by their
carelessness, makes it possible or probable that you will do by mistake. ie
as someone has suggested, if their router is "offering" bandwidth and your
router signal falls below theirs then you may acquire their system entirely
innocently and accidentally. In both cases the systems are probably running
without any security for this to be able to happen.

If a drunk man in a car driving at night runs over another drunk man lying
on the road, the driver is still liable to be liable if it can be shown that
they were not taking due care.

If a sober person runs over a drunk who was lying in the roadway (as happens
occasionally) the same test as above would be applied but the sober driver
is more liable to be able to show that they had taken due care and it was
not reasonable for them to have detected the person lying on the road.

ie Taking due care in normal circumstances is liable to be a defence against
the unexpected. In the WiFi case, operating with eg 128 bit encryption
turned on and a non-default password is liable to protect you against both
accidental intrusion by others and accidental use by your system of other
routers.

The above is of course NOT a good analogy for most of the cases where
non-owned bandwidth usage occurs as in most such cases people are really
looking for some way to excuse the theft of other people's property :-). (As
another different yet not totally irrelevant example, even Bill Gates, no
matter what one may think of his products or practices,  is entitled to
charge what he wishes for his software).



       RM

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2004\08\15@210148 by Steve Willoughby

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On Sun, 15 Aug 2004, Gerhard Fiedler wrote:
> But the OP's case is more analog to the situation where someone lets run
> water out of his driveway onto the (public) street, and then I fill a
> bucket from that stream and wash my car with it. I don't think that there's
> something wrong with that, legally or otherwise... :)

Not entirely.  In the case of WiFi, if you connect to their AP and
use it to access the internet, you're actively drawing from a resource
in a way that interferes with their use.  You're not taking excess
water they've discarded, but have actually hooked up your own hose to
their house and turned it on, reducing the water pressure they have
available to work with as well.

Now, it gets more interesting if they're using an evil ISP which
limits or meters the amount of traffic they're allowed per month :)

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2004\08\15@232907 by Martin Klingensmith

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Russell McMahon wrote:
>>But the OP's case is more analog to the situation where someone lets run
>>water out of his driveway onto the (public) street, and then I fill a
>>bucket from that stream and wash my car with it. I don't think that
>
> there's
>
>>something wrong with that, legally or otherwise... :)
>
>
> In that case the water has left the private property, and the act of running
> over ground has diminished its value. If you replaced water with eg
> chocolate coins in metallic paer wrappings, the analogy may be better. ie
> they retain their value while running down the hill and the owner MAY decide
> to retrieve them. Still not a perfect analogy.

I have to comment on how funny analogies get when people try to come up
with a clear replica of the situation in question :)


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2004\08\15@233947 by Robert B.

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----- Original Message -----
From: "Martin Klingensmith" <martin@spam@spamKILLspamNNYTECH.NET>
To: <EraseMEPICLISTRemoveMEspam@spam@MITVMA.MIT.EDU>
Sent: Sunday, August 15, 2004 11:29 PM
Subject: Re: [OT:] WIFI Ethics?


{Quote hidden}

running
> > over ground has diminished its value. If you replaced water with eg
> > chocolate coins in metallic paer wrappings, the analogy may be better.
ie
> > they retain their value while running down the hill and the owner MAY
decide
> > to retrieve them. Still not a perfect analogy.
>
> I have to comment on how funny analogies get when people try to come up
> with a clear replica of the situation in question :)
>

I agree.  All evening now I've been having dreams of virtually unlimited
quantities of chocolate coins spewing out of my garden hose and into the
street for my neighbors to eat.  Or better, out of my  neighbor's garden
hose for me to eat!

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2004\08\15@235647 by Jason S

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From: "Steve Willoughby" <RemoveMEstevespamspamEraseMEALCHEMY.COM>
Sent: Sunday, August 15, 2004 5:54 PM

> Not entirely.  In the case of WiFi, if you connect to their AP and
> use it to access the internet, you're actively drawing from a resource
> in a way that interferes with their use.  You're not taking excess
> water they've discarded, but have actually hooked up your own hose to
> their house and turned it on, reducing the water pressure they have
> available to work with as well.

No.  Connecting the hose to their house and turning it on would be like
breaking into their secure network.  Logging onto their unsecure access
point would be more like them running a hose to the street and leaving the
water flowing.

Since the router also sends broadcasts, it's like the home owner putting a
"free water" sign next to the hose too.

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2004\08\16@020840 by Russell McMahon

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> No.  Connecting the hose to their house and turning it on would be like
> breaking into their secure network.  Logging onto their unsecure access
> point would be more like them running a hose to the street and leaving the
> water flowing.
>
> Since the router also sends broadcasts, it's like the home owner putting a
> "free water" sign next to the hose too.

Analogy has swung too far.
IF you access their network you may be using resources, whether you know it
or not, which cost them actual resource units of some sort. The hose to
street analogy costs them nothing MORE than the water which crosses  the
boundary. When you access the network you are sucking on the hose.

I have an  analogy that actually comes close but will post it later if it
still feels worthwhile.

       RM

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2004\08\16@073041 by Howard Winter

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Gerhard,

On Sun, 15 Aug 2004 18:57:02 -0300, Gerhard Fiedler wrote:

> > It is certainly contrary to the Computer Misuse Act though, which covers
> > attempts at unauthorised access to someone else's system, among other
> > things.
>
> "attempts": In the OP's case, there were not really any attempts. The
> default configuration of a plain vanilla system connects to an available
> hot spot. The user isn't even aware of that, unless he's some kind of tech
> person, so it can't really be said that he "attempted" it.

Indeed, I never said he did!  I'm sure the legal definition of attempting something includes the fact that it
is deliberate.  I wasn't really referring right back to the OP's situation, but to the discussion points that
followed.

> "unauthorized access": With so many public hot spots that provide (implied)
> authorized access, it is pretty much impossible for a normal user without
> special equipment to determine if a hot spot is authorized or not.

The situation isn't like that here - all the "public hot spots" that I know of now charge to use them, usually
by buying a ticket and logging on with it.  You can't get in free, let alone accidentally!

> In the outside area of an internet café that provides wifi access, most users
> don't have a clue whether they are connecting to the café's router or to an
> unsuspecting neighbor's router. Is that their fault?

If you accidentally / unknowingly connect via someone's private system, then they have taken no steps to
prevent you from doing so, and I don't believe you have done anything wrong.  If they didn't take steps to
keep you out, they are either ignorant of the situation (the usual reason, I'd guess) or they can't be
bothered and consider the effort to do so not worth it, or they really don't mind people using it.  In all of
these cases, it's not your fault and an accidental connection would not be breaking any laws, IMHO.

> Gaining access by breaking an even weak encryption or hacking an even weak
> password is of course a completely different issue.

Absolutely!  The Computer Misuse Act steps straight in there  :-)    And also, if their router pops up a
window on your system saying: "This is Fred's network - unauthorised access forbidden" and you carry on using
it, then you have knowingly perpetrated an unauthorised access, even if you didn't need to crack anything to
do so.  You know you aren't authorised (Fred hasn't told you that you are) so you are definately committing an
offence.

Cheers,


Howard Winter
St.Albans, England

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2004\08\16@113326 by Steve Willoughby

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On Sun, 15 Aug 2004, Jason S wrote:
> No.  Connecting the hose to their house and turning it on would be like
> breaking into their secure network.  Logging onto their unsecure access
> point would be more like them running a hose to the street and leaving the
> water flowing.
>
> Since the router also sends broadcasts, it's like the home owner putting a
> "free water" sign next to the hose too.

Yes, it's true that they're (presumably unknowingly) advertising
for you to come get the "water", but your usage still more closely
resembles a direct tap into their plumbing than using runoff water.

I was just responding to the implication that using the bandwidth
was like passively using water running off, where your consumption
couldn't affect anything.  Or in other words, that you're just
using a resource they've let spill over and will be gone anyway.
In the WiFi case, that might be true if the owner happened to be
idle at the computer (so they wouldn't notice your use) but your
connecting to their AP can draw more resources away from the owner
according to your demand, much unlike using free water which will
flow by anyway.

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Steve Willoughby     | "It is our choices... that show what we truly
<STOPspamsteve.....spamalchemy.com>  | are, far more than our abilities."
                    |     --Albus Dumbledore, in Harry Potter and the
                    |            Chamber of Secrets, by J. K. Rowling

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