[AMRadio] Ultrasonic feedback

[John King]

Can anyone direct me to a source of information or a tutorial on Ultrasonic feedback in modulator circuits such as that in the Heathkit Apache.

My Apache modulator squeals when the microphone gain is raised and the modulator tubes draw a lot of current. As long as the microphone gain is kept very LOW the current does not take off and there is no squeal coming from the modulator section. I am going to go through the section with a screwdriver and a nut driver to tighten up the grounds to the chassis and tube socket.

Ultrasonic feedback is a NEW phenomenon to me. Someone mentioned ferrite beads some time back. Thanks for reading. 73, John, K5PGW