Before getting into the problem description, I have done some homework and know that others have had similar problems, so I'm hoping to tap into some experience. The problem is with high gain in the SSB transmit chain on 40 meters versus 10 meters. Folks often perceive these problems as high ALC indications and distortion.
I haven't used my K2/100 much for SSB in the year that I have had it. Our club has a 10 m net, so I started checking into that and found my Heil mic produced light but adequate audio with around 1 ALC bar showing. VOX was effectively useless. A second mic, a homemade electret, had more audio, moved the ALC about 3 bars and operated the VOX. Mistakenly thinking this was all about mic output level, I made a 15 dB preamp for the Heil, and it seemed to work great. All that was on 10 meters. Last weekend, I decided to give it a workout in the SSB SS contest. Using the Heil and preamp, things seemed to be going great on 15 m, but as I moved down to 20 m, the autotuner kicked in a few times unexpectedly. I was watching the ALC and had noticed about 5 or 6 bars, which didn't strike me as a problem. Nobody complained about my audio, but I think the autotuner action was due to some serious distortion. When I moved down to 40 m, the K2 was clearly red-lined. The ALC maxed, and the autotuner tried to retune on every transmission, when the antenna was well matched already. Finally, somebody let me know that my audio was terrible. The poor fellow was doing me a favor, but he was apologetic. I guess some folks are sensitive about their audio and must bite your head off if you comment on it. I started changing things immediately and asking for audio reports as I went. Compression and gain settings in the K2 didn't really matter. The preamp had to come out of line and the boom mic was turned out from my face to get the ALC reading below 5 bars, and finally, somebody said my audio was OK. I think at this point, the K2 was set for the -10 dB mic gain setting. So I had dropped about 25 dB of gain in the electronics and moved the mic away from my face, pointing it in the wrong direction, before I could get down to 5 bars of ALC. The antenna tuner still tried to retune once in a while, if I raised my voice, so that was the end of the test. I switched to my old TS-940 and let it go. >From reading various posts, it is clear that others have had some problems like this. Either under-drive on 10 meters or extra drive on 40 meters has been talked about on the reflector. My case seems extreme. A variable mic output from +15dB down to -30dB might mitigate it, but this seems a bit ridiculous. Besides, there might be something wrong in the K2 that could be fixed. I haven't started troubleshooting and am I'm hoping for some hints to point me in the right direction. Thanks, Rob -- View this message in context: http://n2.nabble.com/K2-SSB-issue-excessive-drive-tp4068449p4068449.html Sent from the [K2] mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
