Thanks to all for your replies and interest. To answer some raised questions:
(1) The K3 works well (no feedback) with an MH-2 microphone connected to the front panel jack. The problem comes about when any other audio source (e.g., another microphone, or W2IHY Eq Plus) is connected to the rear panel mic jack. Unfortunately, I can't easily connect another microphone directly to the rear jack, without routing it first through my station controller. However, I _can_ route the EQ Plus directly into the rear panel jack, bypassing the controller, and see no change in the feedback problem. I've not had the feedback problem with three other rigs I've tested. (2) My test with the dummy load connected directly to the antenna input on the K3 was intended to establish that RF was not getting into the audio by radiation from coax cables in the shack. My best guess is that RF is "leaking" out of the K3's power cable into my 12V distribution panel, and from there into the audio line of connected devices. (3) I'm not 100% sure that the problem is actually caused by RF. It might be caused by audio modulation of the 12V on my power distribution panel resulting from fluctuations of the DC current when the K3 is voice modulated. One way to check that possibility, which I plan to do today, is to see if the problem persists when the K3 is operating in AM and the power supply current is roughly constant. I also plan to look at the audio and 12V lines with a scope. I'll let you all know what I find. However, since I've experienced no other problems using the identical hookup with other rigs, e.g., a Yaesu FT-2000D, I can't help but think the K3 is abnormally sensitive to this kind of problem. 73, Jim W8ZR _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
