Dear Jacek, Maybe rf is getting into the microphone.I had exactly the same problems here!! There is a wonderful article in the latest issue of German´s FUNKAMATEUR. I´m using the Heil MH2 microphone and I had always problems on 40m with rf getting into the microphone. The modification is very easy: Solder a ground strap (I used a "ground strap" for desoldering), to the ground connection of the microphone and connect it to the metal housing of the microphone connector. This solved all my problems. You can find the whole story in the December issue on page 1280.Hope that helps. 73,Chris-OE5CSP
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