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'[EE] Build a spectrum analyzer'
2011\06\28@110033 by Herbert Graf

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So, in my huge amounts of free time I've been thinking that the one area
of electronics I don't really have much experience is radio.

I've been experimenting and having some fun, but I've convinced myself
that something that might turn out to be a really fun and educational
adventure is building a spectrum analyzer.

There's not of google links out there to half finished or ancient
projects.
I'm not looking at creating laboratory grade equipment, just something
that'll help me see that the circuits I'm building are actually doing.

So, any suggestions?

I'm not to concerned about the interface or display, that's the kind of
stuff I've done before so I'd probably just take the easy way out and
use a PC initially.

My main area of concern is the actual RF stuff.

I'd like the analyzer to at least cover up to about 1GHz (the 2.4GHz
band would be nice (and very useful in the future) but I feel I might be
overreaching there).

Alot of projects use the tuners in VCRs for the RF front end. Any
recommendations on something that might work well?

Ideally if I could get a tuner to do most of the dirty work (something
like feed it a voltage to select which frequency to tune, and output an
RSSI signal to indicate signal strength) that would be a great way to
start.
Any suggestions? Anybody do something similar?

Thanks for your ideas!

TTYL

2011\06\28@110711 by Ariel Rocholl

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Hi Herbert,

That is more or less what I did for RF Explorer, see
http://www.rf-explorer.com . Current versions are limited to narrow ISM
bands, but wider band models are coming in a few weeks, including a 2.4Ghz
and 240-960Mhz.

The circuit is published on the "hacker's corner" wiki. You may get some
ideas out of it.

Hope this helps,

-- Ariel Rocholl
http://www.rf-explorer.com


On Tue, Jun 28, 2011 at 5:00 PM, Herbert Graf <spam_OUThkgrafTakeThisOuTspamgmail.com> wrote:

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>

2011\06\28@111655 by Herbert Graf

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On Tue, 2011-06-28 at 17:07 +0200, Ariel Rocholl wrote:
> Hi Herbert,
>
> That is more or less what I did for RF Explorer, see
> http://www.rf-explorer.com . Current versions are limited to narrow ISM
> bands, but wider band models are coming in a few weeks, including a 2.4Ghz
> and 240-960Mhz.
>
> The circuit is published on the "hacker's corner" wiki. You may get some
> ideas out of it.

Hello Ariel,

neat, thanks!

I've looked at other units that are kinda similar to that. Thing is, I
don't really want to build something restricted to one band, I'd like
something that covers a wide range.

TTYL

2011\06\28@113302 by Ariel Rocholl

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Hi Herbert,

Absolutely, the wider the span, the more fun you get experimenting.

A 1Ghz bandwidth is doable with a tuned circuit in the middle of the band,
and some software tricks to calibrate the results and overcome the lack of
linearity. For wider than 1Ghz bandwidth the tuned circuitry becomes very
complex for a reasonable linearity and cost, and you would find easier to
split the wider band in chunks and downconvert higher part of the spectrum
into lower band, and thus reuse the same tuned circuitry. This is what most
full size SA do, have 2 or 3 IF stages to limit the bandwidth you need to
process after some point.

Cheers,
Ariel

On Tue, Jun 28, 2011 at 5:16 PM, Herbert Graf <.....hkgrafKILLspamspam@spam@gmail.com> wrote:

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>

2011\06\28@114439 by Sean Breheny

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One fairly common way to make a cheap spectrum analyzer for <1GHz is
to use a surplus TV tuner module, the kind which used to be on
computer analog TV input cards. These can be set up to take RF in,
give a single IF frequency out (often 45MHz or 10.7 MHz), and take a
tuning voltage input. These would allow you to tune from about 40MHz
to 1GHz. They also often have built-in AGC with a signal strength out
pin. You then can amplify the output, apply a much narrower filter,
and feed it to a log-amp detector IC. Then, the combination of the AGC
level out plus the output of the log amp would be your signal strength
in the BW of the narrow filter.

I bought a few of these tuner modules on eBay for only a dollar or two
each just a few months ago. They came with documentation, too.

Sean


On Tue, Jun 28, 2011 at 11:00 AM, Herbert Graf <hkgrafspamKILLspamgmail.com> wrote:
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>

2011\06\28@114857 by Herbert Graf

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On Tue, 2011-06-28 at 11:44 -0400, Sean Breheny wrote:
> One fairly common way to make a cheap spectrum analyzer for <1GHz is
> to use a surplus TV tuner module, the kind which used to be on
> computer analog TV input cards. These can be set up to take RF in,
> give a single IF frequency out (often 45MHz or 10.7 MHz), and take a
> tuning voltage input. These would allow you to tune from about 40MHz
> to 1GHz. They also often have built-in AGC with a signal strength out
> pin. You then can amplify the output, apply a much narrower filter,
> and feed it to a log-amp detector IC. Then, the combination of the AGC
> level out plus the output of the log amp would be your signal strength
> in the BW of the narrow filter.
>
> I bought a few of these tuner modules on eBay for only a dollar or two
> each just a few months ago. They came with documentation, too.

Thats exactly the kind of thing I'd like to find! Any pointers? Willing
to sell the ones you've got? :)

How would I go about searching for something like that? The
documentation would of course be key, don't want to try and figure
pinouts of modules on my own?

Thanks, TTYL

2011\06\28@121435 by Derward Myrick

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Hebert,

There is a spectrum analyzer group that has just done a 1 Ghz
unit that uaed a laptop fpr display.
This is the group .....spectrumanalyzerKILLspamspam.....yahoogroups.com <EraseMEspectrumanalyzerspam_OUTspamTakeThisOuTyahoogroups.com>
This is a very good SA not a piece of junk.

look at this URL  http://www.scottyspectrumanalyzer.com/

Derward Myrick   KD5WWI






{Original Message removed}

2011\06\28@123558 by jim

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Check the Radio Amateur's Handbook.  There is a little of everything in
there.  And most of the projects
and equipment in there was designed and built by amateur radio
operators.  And if you know anything about
amateur radio operators, they want to get the most bang from their
buck.  Which means they use more
ingenuity than money, and design needed equipment to do a job well, but
not necessarily fancy.  And they
do it on the cheap.  Cheap meaning inexpensive, not low quality.

Regards (73),
Jim (KA9QHR)

> ---{Original Message removed}

2011\06\28@143834 by Sean Breheny

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Hi Herbert,

Try searching for "tuner" under the business&industrial category on
eBay. I just did that and found several, although the only one which
had a datasheet link was a digital-output tuner for DBS. However, most
likely some of the others have datasheets which can be found online.

I will take a look to see if I can find the ones I got and I may sell
them if I can find them.

Sean


On Tue, Jun 28, 2011 at 11:49 AM, Herbert Graf <hkgrafspamspam_OUTgmail.com> wrote:
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>

2011\06\28@161834 by Bob Chadwick

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Go have a look here. Somewhat dated; I don't see anything that indicates
recent updates, but a lot of good data and links. http://www.nitehawk.com/rasmit/sa50.html

Bob Chadwick
PICList Lurker



Herbert Graf-5 wrote:
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> -

2011\06\28@172619 by Derward Myrick

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Herbert, look at this http://www.science-workshop.com/

This one goes 2150 mhz.

Derward Myrick




{Original Message removed}

2011\06\28@183253 by David Bley

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Well I looked at my Google Bookmarks and found this:  http://scottyspectrumanalyzer.com/

While not a spectrum analyzer, a component of a VNA is a comb generator, found here:
http://www.thegleam.com/ke5fx/cg.htm

Instead of searching for spectrum analyzers, you may find more help looking for VNA's.  There are several of those projects on the 'net, although they don't make it to 1GHz.
http://sdr-kits.net/DG8SAQ/VNWA/baier_VNWA10_QEX.pd

2011\06\28@215421 by Dwayne Reid

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At 09:00 AM 6/28/2011, Herbert Graf wrote:
>So, in my huge amounts of free time I've been thinking that the one area
>of electronics I don't really have much experience is radio.

I played with the science workshop spectrum analyzer <http://www.science-workshop.com/> many years ago and wasn't all that happy with it.  I don't remember the details but one major problem was inability to calibrate the frequency accurately.  It was useful to get a general idea of what the spectrum looked like but that was about it.  The last time I used it was probably 10 years ago.

I've been using an old HP 8559 for the past many years but late last year, I finally bought something better: its called a Signal Hound <http://www.signalhound.com> .  I also purchased its companion tracking generator when they became available early this year.  Both go up to 4.2GHz..

If you do purchase one of the Signal Hound units used, make sure that you get the "B" version.  The earliest units (non "B") spew significant amounts of the first LO out the input connector which can (DID!) cause significant problems.

I also recently purchased a VNA (vector network analyzer) from <http://www.SDR-kits.com> .  This is a NICE little box that does one and two port measurements.  It will function as a rudimentary spectrum analyzer but there are limitations that are at least well documented.  Its good up to 1.3GHz.

Both of the units I mentioned are fully assembled, not kits and not parts collections that can be gathered up.  Sorry about that.  But they both work well.

dwayne

-- Dwayne Reid   <@spam@dwaynerKILLspamspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\06\29@013018 by Sean Breheny

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part 1 2331 bytes content-type:text/plain; charset="iso-8859-1" (decoded quoted-printable)

OK, I looked at what I have and it is less impressive than what I
remember. Frequency range is only about 400 to 900 MHz. I have
attempted to attach a GIF image which I was sent by the eBay seller
when I bought them (qty 2). I also have a schematic but please ask me
offlist if you want it as it is a little bit bigger file and I do not
think that I should try to send it on-list.

Also, I came across this archived discussion on this topic of spectrum
analyzers from TV tuners:

http://www.nitehawk.com/rasmit/sa_notes1.html

The modules I have were made by Mitsumi, they have only one label on
them which seems to say TIF4-A41. Also appears to have a date code of
8447 (47th week of 1984 I'd guess). These are probably not the best
bet for this project as there are more modern ones available, some
even with I2C-controlled digital tuning.

I would be willing to sell them if you are still interested.

Sean


On Tue, Jun 28, 2011 at 11:49 AM, Herbert Graf <KILLspamhkgrafKILLspamspamgmail.com> wrote:
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2011\06\29@040017 by Peter Loron

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I've got a pile of Sharp tuners (or at least they look like tuners). I don't have any data on them. Link to an image is below. If you're interested make me an offer.

http://standingwave.org/webdav/xe6095.JPG

-Pete


On Jun 28, 2011, at 10:29 PM, Sean Breheny wrote:

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