I noticed an AC hum in the monitor audio in my headphones while calling with one of the W1AW portables. While wondering if the hum was really in my transmit audio, the W1AW Operator came back to me and reported the hum. I use a Heil Proset K2/K3 via the front panel microphone connector through a Kenwood style (red band) Heil pigtail. After completing the QSO I switched to Test mode and I could still hear the hum when I transmitted. Thinking I had a poor connection, I disconnected and reconnected both ends of the pigtail, but the hum persisted. While doing that I noticed there was no hum if I activated the push to talk with microphone unplugged from the pigtail. That had me baffled for a few moments until I remembered that the Proset K2/K3 requires bias voltage from the K3. At that point I used the "2" button in the "MIC SEL" menu to turn the bias off and on a few times and the hum was disappeared. I haven't researched the details of the bias switching arrangement in the K3 but it appears that mine needed some exercise to clear a bad connection. I thought I would pass this on to the rest of the group in case someone else encounters this issue.
73, Bill - NA5DX ______________________________________________________________ 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]
