Mic levels: FM versus other voice modes

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  • Updated 4 years ago
Running SSDR on a 6500 and listening to the Xmit signal with a Ten Tec RX-350 receiver (no overload to rcv!).  In AM / SSB modes the audio from a Heil PR-40 ->Tube preamp -> Balanced input  sounds very good ("that +20dB mic gain" : OFF).  FM is a different story, hardly any audio / modulation.   Using a Ten Tec-707 mic to the mic input with "that +20 dB Mic preamp": ON the audio quality on all modes is outstanding.  

In summary, FM XMT modulation seems to only work well with the Mic input and not other inputs.
Has anyone else observed this?

Doubtful it's RFI related as testing was at 2 watts and other modes had no problems at 2W to 100 W.  Also the mic input worked fine with FM  @ 100W.

Thanks for any insight...

Note on AM XMT:  Someone posted comments about the XMT AM not sounding good on the 6K series.  Well this particular box sounds like broadcast quality AM!  I heard a 3k series on 80-M and the gentleman had outstanding AM quality.  When using a linear one has to be super careful, but I think we all know that.

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Posted 4 years ago

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