That didn't fix it. Found this lunchtime with a real antenna: - Worked OK with case open, testing the idea it was coupling from the 2m module itself. - Worked on other mic (SoundMagic earbuds and mic) - Touching the case with metal made interesting noises on receive. - HF (20m) seemed OK, if I take the response "America only please" as indicative the other station heard me and my signal was good enough for him to tell I was not in America.
- Richard On Wed, 5 Feb 2020 at 22:07, Richard Corfield <[email protected]> wrote: > The metal shield cover on the 2m module was not flat but slightly raised > at the edge. I have pressed this back on and the problem seems cleared. So > I guess it was contacting or coming close to the circuit board on the > control module, perhaps that giving the feedback loop for RF. Question is - > could any damage have done if it had contacted the vias/pads on the board > there? > > - Richard > > On Wed, 5 Feb 2020 at 21:01, Richard Corfield <[email protected]> > wrote: > >> I've done some further tests and proven the problem is with the MH3. So >> I'll have to take that apart and look for the problem. >> The radio is fine with little earbuds/mic plugged in via splitter cable. >> Swap out the mic on the earbuds with the MH3 and leave all the rest the >> same and it goes wrong. >> >> Thanks >> - Richard >> >> On Wed, 5 Feb 2020 at 15:29, Nr4c <[email protected]> wrote: >> >>> 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]
