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Old 19th Aug 2019, 6:24 pm   #3
G6Tanuki
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Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,951
Default Re: Spitfire Am Transmitter Hum (Buzz)

I'm thinking that this could be a form of "Modulation Hum" where something-mains-powered-in-the-house has diodes in it and the RF from your TX is passing through them as they're switching, so impressing 50/100Hz hum on the RF which is subsequently re-radiated by the wiring and picked-up by your radio.

In the past I had a 3-way 13A adaptor that had been gutted and the insides replaced with a triangle of 0.05uf capacitors (Live-to-Earth, Neutral-to-Earth, Live to Neutral) that I'd plug in to various outlets to see if the problem reduced - if it did I'd check anything plugged into nearby outlets. Alas in these days of RCDs the increased earth-leakage this caused often resulted in a loud CLICK! from the distribution-panel followed by radio-silence.
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