Testing Radio Gear
Scotty Sprowls (SCOTTY)
on
January 27, 2004
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Amateur radio gear has sure come a long way in the past many years -- so many varieties of gear, readily available from many manufacturers. But what about the Ham who wants to do stuff the "old fashioned way"…build it. Along with building comes testing. How many builders have equipment in their shop to test a transmitter's harmonics, or even the "notch" in a cavity filter? Very few, I'm sure.
I certainly had that problem, and I decided to build an RF Spectrum Analyzer. There are quite a few very nice designs that have been published and are accessible on the Internet. But I wanted to try something a little different. Instead of using an oscilloscope for a display I wanted to use my computer display for a graph. That way, I could save a copy and print it without the need for a "scope" camera. One thing led to another and I was able to let the computer do all the frequency commanding. The RF and Analog circuitry for my analyzer is very similar to others, but the computer does all of the processing. Sure made for a small, compact Spectrum Analyzer.
This was such a fun project, and it turned out so well, I wanted to share it with as many experimenters as possible. I added a link in the Ham Links, Homebrew section for you to get to my personal site for full information on my results. Or go directly there at:
http://users4.ev1.net/~wsprowls/
All are welcome to use the information in any form. Republish, if you like. I will try my best to answer questions and give tips on construction. I am retired, and, although not a radio amateur, I have answered a few questions in the forum on radio repair questions. Enjoy. Scotty.
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Testing Radio Gear
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by K0BG on January 27, 2004
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Not for everyone, but nonetheless a good project for those who like a challenge.
Alan, KØBG
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RE: Testing Radio Gear
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by N7UQA on January 27, 2004
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Now this is cool guys. This is what ham radio is all about. I personally have several pieces of test gear but getting a decent spectrum analyzer is almost impossible. I have two Tektronix 2465's, Motorola com analyzer, HP 5328A and a Fluke 8060A but still lack a 9KHz-1.5GHz spectrum analyzer. Something like this would be a viable option for thoes inclined to build one..
Craig - N7UQA
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Testing Radio Gear
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by WM5Z on January 27, 2004
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Great article! Have you thought about offering a kit? Even though I have a couple of spec-an's here, I would enjoy building something like this. I just don't have time to go looking for the parts. Have you thought of adding a narrower filter, like something on the order of 250 to 500 hertz? Then bessel functions could be observed to calibrate FM equipment.
Steve/WM5Z
wm5z@yahoo.com
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Testing Radio Gear
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by SCOTTY on January 27, 2004
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Thank you (so far) for the nice comments and emails. I am retired, lazy, and not at all wanting to get into the production business. If someone in the kit business is interested in doing this, I would be thrilled to help them out, in any way, to get this Spectrum Analyzer into as many home-brewers' hands as cheaply as possible. This may sound crazy, but I am not interested in making money off this thing. I really enjoy playing in my shop and this project was not only entertaining, but quite a nice addition to my test equipment.
As far as a narrower filter goes, you certainly can go as low as you want. You could use one of the radio Mfg.'s narrow band filters such as the Kenwood YK-88C (500 Hz) or YK-88CN (270 Hz) as the Final Xtal Filter. It is centered at 8.83 MHz and with tweeking of the cavity filter, they would work just fine.
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Testing Radio Gear
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by N4ZOU on January 27, 2004
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WOW and double WOW. I got to build this! The power supply finally died in my 7903 with no hope of repair. It's still on the shelf with several diffrent plug in modules as I think I would miss it after all the years of good service it has performed. Where's that mouser CD? I need to build a replacment!
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RE: Testing Radio Gear
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by KG4VPV on January 27, 2004
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You are my hero. I dont have a lot of money to blow on a spectrum analyzer, but I can definitely use one in the shack. Imagine how many students would love to have something like this!
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Testing Radio Gear
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by W5GNB on January 28, 2004
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Thanks for the terrific article and demonstrating how simple a supposedly difficult project can really be. Now you need to get that HAM license HIHI....
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RE: Testing Radio Gear
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by KC2ELS on January 28, 2004
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The only thing keeping me from trying something like this is that I don't know how to port Liberty Basic to C for Unix.
Any interest in increasing your target community? Let me know.
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Testing Radio Gear
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by SCOTTY on January 28, 2004
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I know there are some users out there who would prefer to run the probgram in something other than Basic. I am already in contact with one amateur who is going to rewrite the code in C++. In a final form, I know a C++ program will run on Unix and probably even Linux. With a little prodding, those who rewrite the code may make their final programs available to all of you who want them. If those programs become part of my website, I promise you they will be free for your use.
I will also say that my website is not finished. I recently added the Spectrum Analyzer Controller for those of you who already have an analyzer that uses a 'scope as a display. I am going to add another spectrum analyzer that utilizes a tv or cable type tuner. The software will remain, essentially, the same. I am am delayed on that right now, as I smoked the only cable tuner I had. I will continue on the protype as soon as I find another tuner.
Best wishes to all, and again, thanks for the comments.
Scotty Sprowls
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Testing Radio Gear
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by N6MON on January 30, 2004
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So, has anyone gotten started on designing PC boards for this? Looks like a great project, but my
breadboarding skills are REAL rusty. A nice set
of boards (that I am SURE FAR circuits would love
to carry!) would be REALLY cool!
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Testing Radio Gear
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by AH6GI on January 30, 2004
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I'm interested.
I can easily handle the software side to this. I have an M.S. Computer Science and am a professional software engineer.
I'd really like to see someone or several someone's turn the design into a kit.
I'll open my list, groups.yahoo.com/group/kitstuff to help with email based discussions and support for this.
de ah6gi/4
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Testing Radio Gear
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by AH6GI on January 30, 2004
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I'm interested.
I can easily handle the software side to this. I have an M.S. Computer Science and am a professional software engineer.
I'd really like to see someone or several someone's turn the design into a kit.
I'll open my list, groups.yahoo.com/group/kitstuff to help with email based discussions and support for this.
de ah6gi/4
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code conversion.
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by AH6GI on January 30, 2004
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Nice looking basic.
the conversion to C or C++ is straight forward except that the UI is tied to the OS.
The UI is the messy part of these kinds of projects.
de ah6gi/4
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Testing Radio Gear
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by K1ADW on January 31, 2004
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The project looks great!
I just wanted to add to the thread about the user interface and OS's. If you write it in something like Perl/Tk, you can create a user interface that can be run under Unix(Linux), Windows, etc. without recompiling. If you have to rewrite it anyway, you might want to shoot for a wide audience.
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RE: Testing Radio Gear
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by K1CJS on January 31, 2004
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Thanks, Scotty. A really great article. If nothing else it reminds us that there still experimenters out there, and that is what a big part of ham radio is about--experimenting! I've got to build this--along with the various other projects I have on the burner, or in my case, the stovetop! ;-))
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2.4 ghz cheap enough
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by N1YRK on February 3, 2004
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I have seen a hardware/software combination on ebay, that uses an 802.11b card and PC to make a 2.4ghz spectrum analyzer. I should find out if I can get the software alone, as I already have several 802.11b cards.
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Testing Radio Gear
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by SCOTTY on February 4, 2004
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I have been in contact with several amateurs who have started work on this Spectrum Analyzer. They are either in the planning stage or have actually begun construction. I thought it would be nice to have a group forum for everyone to exchange ideas and comments. I will still answer personal emails, but if you would like to contribute and look over everyone's shoulder as they proceed, go to this open group page.
http://groups.yahoo.com/group/spectrumanalyzer/
Have a swell day, all.
Scotty Sprowls
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Testing Radio Gear
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by WA2JJH on February 5, 2004
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Nice piece of work. I had once built a spectrum analyser out of a varator TV tuner and sweep generator.
It did not work!
Glad I have my Old WAVETEC-3000B.
Your design is very novel.
I might try this one, if I have the time.
TNX for showing that homebrew is still alive, despite what many say!
73 DE MIKE
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