[R-390] Single Sideband reception with the R-390/R-390A

[DJED1 at aol.com]

Thanks for the comments on SSB adapters, Dan.  I'm really happy with  my 
outboard SSB adapter for all the reasons cited (I did add the crystal BFO,  per 
AI2Q).  As Les indicated, you haven't solved the problem unless you've  solved 
the fast attack AVC part of  it- a product detector is not  enough.  My 
outboard SSB adapter does that, and it is integrated with  the receiver so all 
controls and the carrier meter still work as intended.   It always aggravates me to 
read Jan Skirrow's description of his outboard box,  which copied my design, 
then says how mine never worked.  But he left out  the AVC circuit, and so 
needs to ride the RF gain to keep from overloading the  detector.  $150 and no 
real improvement over how the stock radio  operates!  
I've continued to play with the concept. I've breadboarded a circuit for  
synchronous detection, and will add that to the box if I ever finish my wife's  
"to-do list" for this winter.  
Incidentally, I built another version with a downconversion and 100 Kc  
filter for sideband selection, kinda like the CV-591.  It worked well, and  doesn't 
require offsetting the BFO to change sidebands (BFO is fixed at 100  Kc).  
However, the radio must be set at the 4 KC bandwidth, and so  signals bleed 
through into the IF and meter circuit. I didn't like it as much as  the original, 
so reinstalled the original box.  I think the audio is better  than my R4C, 
although the AVC is not as tight as the Drake.
Ed WB2LHI