I started out playing with a SDR dongle back four or five years ago when you had to order them through eBay, from Hong Kong. That first one had serious frequency stability issues… it would drift 30 ppm if you breathed on it, or held it in your hand.
A lot has happened in the intervening years, and I just picked up one of these from Amazon…
The major improvement with this one is a temperature compensated crystal oscillator. I have yet to see it drift even 1/2 ppm.
All these cute little SDR’s have to be installed with a rather convoluted set of drivers… on my Win7 box, there is a zip file with a batch file to run. Took me several tries to disable firewall and antivirus settings to allow it to pull off the web what was needed.
The best on-line resource, and a very good quick start guide, is available here:
There is a constant stream of articles on the site by people who are using them for everything but the kitchen sink. One of the favorite things is to set up an ADSB receiver on 1080 MHz and receive aircraft navigational squawks. Real-time mapped representations of local air traffic.
(only one example of MANY applications.)
The versatility can be extended down into the short wave and medium wave bands with the addition of an upconverter/mixer. I use this one:
One of the serious shortcomings of these little dongles is a wide-open front end. Here in the SF East Bay, I get images of KCBS 740 AM all up and down the short wave spectrum. I’m building a band-stop elliptical filter to get away from those strong signals…
(BTW the author of that article is Carol Milazzo, amateur radio call sign KP4MD who lives in Citrus Heights, is a medical doctor, and designs her own home-brew ham gear in her spare time. Quite a lady!!)
For those who want to do weak signal work in close proximity to a broadcast FM Station, a similar dilemma happens on the upper frequency range. Here is a nifty little band-stop filter out of Greece, available on eBay for less than $20, that should prove useful. It’s on my wish list….
So there is a LOT of fun to be had for not very much investment.
The limitations with these dongle are pretty severe… only 8 bit A/D conversion for instance. Other SDR receivers quickly escalate in price and sophistication. Here is a comparison of several of the slightly more expensive options.
Personally, after reading this lengthy and detailed article, I think there is an AIRSPY in my future…
I’m thinking that one of these dongle setups could be quite a catalyst for interest for a young person.
Follow the link to QRZ below if you want to check out my bio.
Glen Rickerd NO6W