I was programming the ProgRock2 for the local oscillator frequencies for reception of local aviation channels. I don't recall them specifically right now, but they were in the aviation band 118 and 137 MHz. The noise was on the operating frequencies not the LO frequencies and seemed to be coming out of the microcontroller itself (not harmonically-related to the outputs). All the interesting frequencies (example 123.45 MHz) that I tried had some interference - but of course my most desired local airport frequencies seemed to be the worst (thanks Murphy).

I tried putting it in a shielded box and bypassing the power wire, but the interfering signals still got out of the box on the output line (along with the desired LO signal). I added a low-pass filter but without a tight-fitting shield on that it still radiated lots of interference. At that point I remembered I could just turn on a scanner and I gave up.

Self-interference can be a significant problem for receivers since the desired signals are so weak. Another irritating example is how the Czech Telsa RF-10 radios PLL sometimes interferes with reception on 51.0 MHz - the one frequency I want to use them on!

Steve WD8DAS

[email protected]

http://www.wd8das.net/

http://af4k-crystals.com/

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On Monday, March 25, 2024 at 03:14:23 PM HST, <[email protected]> wrote:

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