John, Not sure about the Apache, but I do have a Viking II here and the manual tells you to reverse the modulator plate connections if you hear a squeal from the modulation circuit.
Sorry if I am off topic too far. 73's Roger KC8OPP --- On Mon, 2/2/09, John King <[email protected]> wrote: > From: John King <[email protected]> > Subject: [AMRadio] Ultrasonic feedback > To: [email protected] > Date: Monday, February 2, 2009, 9:56 PM > 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 > > > > > > > ______________________________________________________________ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: > http://www.mail-archive.com/[email protected]/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: [email protected] > To unsubscribe, send an email to > [email protected] with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: > http://www.qsl.net/donate.html ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
