Re: Tracing receive signal for low signal

Dave Space
 

I had that pre-amp earlier in the receive line between K3 and K1 and what I noticed that amp vs the new pre-amp I put in at volume high  is the pre-amp between K3 and K1 just sounded like it amplified the noise as much as the signal making the noise as loud as the signal.  Where the amp at vol high seems to have done a better job picking up the signal and less noise (at least if I don't have the gain too high).
I think maybe because the low pass filter rejected a bunch of noise so the amplification stages amplified less of the noise (at least that's the best way I could describe it from a noise quality I can hear).  Thus why I was thinking it might be better to amplify after the low pass filters (it probably lost some signal there also anyway).

What I'm thinking is two transistor stages common emitter then emitter follower to get the low output impedance for following Q12 (so common emitter + emitter follower )and Q32 (common emitter + emitter follower)

The only other way I can think of to track down the board differences is buy a second uBitx board that hopefully works (though I'd be hosed if it didn't) and just analyze component by component all the way through until I find something with a meaningful difference.

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