Thanks to all who responded. This morning I got a significant clue: Following up on Tony Fishpool's suggestion, I separated the power supplies: I ran the RF amp, oscillator and mixer base bias off a small 12 V battery, with the mixer collector circuit and the AF amps running of the bench 12V supply. The AF oscillations completely stop under these conditions. So the feedback is probably taking place via the 12 V supply lines. 73
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Carlos’ Illustrated Radio Listening Report and Recording of NHK (July 24,
2025)
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Many thanks to SWLing Post contributor and noted political
cartoonist, Carlos Latuff, who shares the following illustrated radio
listening report of a rece...
5 hours ago
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