Re: An all tubes FM tuner with permeability tuning device.
It looks like you are enjoying the adventure!
50 Hz modulation is likely pick-up from the heater circuit, if your HT is filtered well. Is there any wiring common to both the heater circuit and the oscillator ground connections.
Or, 50Hz field from heater current can modulate the permeability of your cores a little, but enough to inject FM hum.
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
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