[R-390] Product detector

[Larry H]

Alex, nice unit.  Major advantages of your unit is no R-390A mods, you provide AGC to the R-390A,  and you use the R-390A audio.  I like that you are feeding the audio out of your SSB unit back into the R-390A  noise limiter input on contact 15.  There is one issue though.  In order for the R-390A noise limiter to work correctly, it requires a negative bias in relation to the received signal strength.  In AM mode this is provided by the diode load signal.  But it should work fine with the N/L turned off.  If you wanted to use the n/l, you could add an agc derived bias to the audio out.
Regards, Larry