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PICList Thread
'Cheap 900MHz RF low-speed short-range data solutio'
1999\04\28@131933 by John Payson

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Does anyone here have any experience with using 900MHz RF data devices?
I'm looking for a short range (<20ft) transmit/receiver pair that can
easily be used to send an "activation" signal.  This would be for use in
a consumer product, so FCC approval is essential.  I've seen various 314Mhz
devices [e.g. the Ming thingies] which would be adequate except that they're
not FCC approved and I can't find any specs about what one can transmit at
that frequency.  The 900Mhz band is basically a free-for-all, and at 20' it
shouldn't be too hard for a transmitter to win out over other users of that
band.

BTW, this application won't necessarily be line-of-sight.  If it were, I'd
use infra-red.

1999\04\28@132730 by Harrison Cooper

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Long time ago...in a galaxy...wait...thats a movie.

Long time ago...when the guru Andrew Warren was around, he and I had some
discussions on what needed a license, and what did not.

Basically, anything that is telemetry, like alarms, or an "are you alive"
signal does not need a license.  If it was a RS232 link, it would because
now its data, and data eats up bandwidth, etc.

I have used DVP modules, with good success (external antenna tho).

{Original Message removed}

1999\04\28@150115 by drcman

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part 0 1851 bytes content-type:text/x-vcard; charset=us-ascii; name="vcard.vcf" (decoded 7bit)

Harrison Cooper wrote:

> Long time ago...in a galaxy...wait...thats a movie.
>
> Long time ago...when the guru Andrew Warren was around, he and I had some
> discussions on what needed a license, and what did not.
>
> Basically, anything that is telemetry, like alarms, or an "are you alive"
> signal does not need a license.  If it was a RS232 link, it would because
> now its data, and data eats up bandwidth, etc.
>
> I have used DVP modules, with good success (external antenna tho).
>
> {Original Message removed}

1999\04\28@160149 by Julian Fine

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Hi All,


>Micrel Semiconductor has just released some impressive chip that can do
just as
>you asked with fewest components around. I'm currently going to do the same
>thing when I get to that part of my project.


Try a lot before you buy.
We were stil busy on the micrel 001 433 Mhz when a month later they brought
out the micrel 001a then 3 weeks later the micrel 002 and a bit later the
micrel 002a.
Basically we told them that when they decide which product they will
stabilize on we will buy.
Beware they are a bit noisy.

************* Julian Fine ***********
********** spam_OUTjulianTakeThisOuTspamfine.co.za ********
******* http://www.fine.co.za *******
** http://www.eagle-wireless.co.za **

1999\04\28@162652 by Peter Grey

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At 12:19 PM 28/04/99 -0500, you wrote:
John,

Have a look at
http://www.ozemail.com.au/~martech/ai.htm

Probably a bit of an overkill, (range 200-250 metres line of sight) but has
passed FCC tests, can work with non-line of sight, is at 900MHz, is a
transceiver and is small.

I do not know of any other radios that are approved in this band.


Peter
{Quote hidden}

1999\04\28@163708 by Peter Grey

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At 11:26 AM 28/04/99 -0600, you wrote:

I made some enquiries on this and I am told that all intentional radiators
(any
transmitter) must be tested by the FCC no matter which band is used. There may
be some confusion with the bands as some are allowed for use of "activation"
but no data. This rule applies regardless of power levels or frequency.In the
900MHz band you are allowed to use data or activation.

Peter

{Quote hidden}

>{Original Message removed}

1999\04\28@183309 by Craig Lee

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I know several, but am most concerned with the per unit price and form
factor.

Er, do you know the price on the hopper unit?

Does it have 5V levels for direct interface to a PIC?

Craig

> {Original Message removed}

1999\04\28@190420 by Peter Grey

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At 04:32 PM 28/04/99 -0600, you wrote:
>I know several, but am most concerned with the per unit price and form
>factor.

You have the foot print from the web site. Price is US$89 each in small
quantities. I know it is above most transmitters and receivers but you do
have to integrate these. With this unit all this is done for you. Just
communicate with it via a serial and don't worry about RF.

>Er, do you know the price on the hopper unit?

Sorry, not yet. It should be relaesed around 3-4 weeks.

>Does it have 5V levels for direct interface to a PIC?

Yes, I have used it a number of times in this way.

Good luck

Peter.

>Craig
>
>> {Original Message removed}

1999\04\28@225039 by Craig R. Autio

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-----Original Message-----
From: John Payson <.....supercatKILLspamspam@spam@CIRCAD.COM>


>Does anyone here have any experience with using 900MHz RF data devices?


Why not roll your own transmitter and receiver.  Check out RF Monolithics,
the manufacturers of SAW devices.  They have good application notes and are
very nice people.  When we did our first project, they provided assistance
in the design phase to ensure compliance.  After that, we did everything on
our own.  The cost is extremely low.  A transmitter should be $5 including
case and battery.  The receiver should be similar.  We have done 303.xxx,
418, 902.5, and one other 900 MHz.  The regulations are on the web.... CFR
(Code of Federal Regulation), I believe 49, part 15.  The power levels are
all there and the forbidden bands, labeling requirements, etc.(I don't have
the webpage handy at home).  Data bit rate and "total accumulated ON-time"
affect power levels (averaging factor) so you should plan your protocol.
AFAIK, unless things have changed recently, once you put your "project"
around someone's embedded transmitter, you still have to get your product
certified.  Even though we have used the same receiver (read copied exactly)
in another product, we had to certify each product separately.
Conversations with the FCC sometime ago when we were planning a family of
products with exact same tx/rx stuff, the feds were considering certifying
our company transmitter for use in our own products under one certification
process but it never flew.  That way you could roll your own and use it over
and over in your own products.  FCC certification is not cheap though.

Craig

1999\04\29@100926 by tmariner

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There are a few modules at 900 MHz that meet your qualification for "cheap":

       RFM - AM modulation, separate TX, RX modules and a new transceiver.
       Linx - FM modulation, separate TX, RX modules.
       RFMD - AM, FM, SS separate, transceivers. (May need more hardware layout
expertise.)
       Innovonics - Spread Spectrum separate TX, RX. (Generally no need for FCC
approval because they handle modulation, etc.)
       Roll your own - See Craig Autio's post. (Requires Craig's skills and/or
access to outsourced design talent.)

All products containing intentional radiators need FCC approval if you can
vary the RF stream. The reason one would design in 900 MHz is that there is
more freedom for the type of data transmitted and the power can at times be
more. The lower ISM bands generally require fixed ID information -- If one
wants to send "telemetry" varying data 900 may be for you.

Tom

> {Original Message removed}

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