[R-390] Product detector

[Larry H]

 Jacques,  

Your 1st Q:

 What if we let the AM detector output connected to the limiter control (R120, term 3) at   all times, but we feed the output of the SSB demodulator to R527 ?
A: That would work if the bias out when receiving ssb were high enough, but it's only a 1/4     of what is needed.
Your 2nd Q:
 In your opinion, does the negative voltage produced by the AM demodulator alone can be   sufficient for the limiter when SSB signals will be received ?

A: Unfortunately, no.  The limiter bias needs to be 2x the peak of the audio input.  This       level is important for the limiter to work correctly.  Too low = distortion, to hi =         impaired limiting.

Your 3rd Q:
 What about also changing the R527 value to 62k ?
A: This will just reduce the level of the audio in to the limiter.  This will cause reduced     fidelity out of the limiter due to the signal level being too low for it's design.

Your 4th Q: I remember having read something about to reduce the limiter stage distortion.

A: Yes, the bias on the limiter needs to be increased a little bit (about 1.4v) from the       original design.  I added a 2.4 k res between S108B #7 and the junction of resistors         R532, 533, & 534.  I only did this mod after verifying my limiter components were all       working correctly.  It did work correctly before, except on strong AM stations.  And, I     have seen a slight improvement in sound quality on all signal levels.

Regards, Larry