Turn down TX Monitor volume. Sent from my iPhone ...nr4c. bill
> On Feb 5, 2020, at 5:23 AM, Richard Corfield <[email protected]> > wrote: > > I had issues with RF feedback on the MH3 during the UKAC SSB 2m contest > last night. It seemed intermittent. Result was terrible noise in Monitor > output (my headphones) and to the other station, so it affects the audio > input. With experiments at the time and this morning: > > > - Occurs when RF power is increased above 0 and when Mic Gain is > increased. I could operate with Mic Gain set low, obviously at reduced > power out. (Indicative of a feedback loop) > - Occurs with a dummy load. (Also when I moved the antenna away last > night). So is the loop internal or is it so sensitive the small leak from a > dummy load is enough? > - Does not occur if I feed a stage Mic In through a field mixer (kit I > have to hand). The field mixer claims an output impedance of 150R and is > running at mic level to match the MH3 allowing same gain setup in the KX3. > Mic Bias is turned off in this case. > - Does not occur on HF into the dummy load. > - Manifests as buzzing on 2m FM > - May result in phantom button presses on the KX3 Mic (I didn't think I > knocked the dial) > > As an aside - one station last night was loud enough to activate the "RX" > indicator which I take to be input overload. S meter was well over S9 but > not at the top. I didn't see anyone else at the site, unless they were > hiding the the woodland carpark but I saw no light there or on the summit > behind me. I hit ATT, should have swung the beam to try to null them. But I > guess the ATT and even maybe the input protection is after the 2m module's > input? > > My thought is I need to inspect the wiring in the mic. Or could there be > anything else I need to check? > > Thanks > - Richard > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
