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Old 6th Oct 2019, 7:38 am   #3
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,800
Default Re: Ferrite rod antenna and RF amp for Valve radios

Try a 'stopper' in series with the connection to the transistor base. With the emitter fully decoupled like that, its input impedance can go negative resistance at HF. This can cause oscillation with no obvious feedback path.

Otherwise try the circuit in a screened box.... feedback could be coming from radiation from the subsequent radio as well.

David
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