I've been meaning to try this for a long time. Years ago Tony Fishpool and Graham Firth wrote about using a noise generator and a spectrum analyzer to sweep the bandpass of a filter. The idea here is to send very broadband noise into a filter, and then use a spectrum analyzer to see which frequencies make it through.
I thought about building a noise generator like the one in Tony and Graham's book, but then it occurred to me that probably had one sitting on my bench. Sure enough, a look at the manual for my cheap FeelTech function generator revealed that PRESETS 3 and 8 are noise generators. I quickly pulled out a 9 MHz filter that Dean KK4DAS had given me, put the noise into one end and the TinySA on the other end. Bob was quickly my uncle. See above.
More recently Tony G4WIF built a comb generator as a noise source:
Thanks to Tony, Graham, and Dean. And to the folks who developed the TinySA.
Bill, this is the RF equivalent of connecting a white noise source to an audio graphic equaliser and pushing up one channel.
ReplyDeleteMy SDRPlay RSP1A has a spectrum analyser software, which supports an external tracking generator, however, no details. I tried a broadband RF noise source and as you report and show, I found it very effective. I don't know I'll bother to try to get a tracking generator now, at least not for HF.
PS See EMRFD Fig 7.72 for a broadband RF noise source you can build in an hour.
-- VK3HN