The front panel "gain" control is for the speech clipping gain. If you turn it up too high, depending on the setting of the "real" audio gain control which is located behind the key jack, the modulator will squeal. This is barring any other electrical or component issues.
Pete, wa2cwa http://www.manualman.com > > --- 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
