[R-390] R-390 SSB Product Detector mods?? Not A

[DJED1 at aol.com]

Peter and list
I'd certainly recommend the AI2Q unit if you're up to building it.   Alex 
based it on my design using a capacitor-tuned BFO.  I've been using  mine for 
several years and have done a couple of modifications.  I'm  happiest with the 
last, which uses a R-392 BFO coil as the oscillator.  I  checked the stability 
and it's just as good as the original R-390A  oscillator.
I modified my circuit to use Alex's crystal BFO several years ago, but I  
like the tunable better.  It depends on your preference- the crystal is  easier 
to use-just flip the switch.  However, my  crystal  frequencies are a bit off 
for the correct edge of the 2 Kc filter so I lose the  lows on one sideband, 
and are obviously not at the edge of the 4 Kc  filter.  With the tunable BFO, 
you can set it exactly to the edge of the  filter.  
I had two objectives when I designed the SSB adapter, to make it work  
without and mods to the radio, and to provide both a product detector and a fast  
attack AVC.  It works great and will handle very strong signals.  The  AVC is 
not quite as flat as my R-4C, but the original AVC on the R-390A is not  very 
flat either.  
Unfortunately, this is not available except as a build-it-yourself.   
However, I can provide help if you have problems.
Ed  W2EMN  (formerly WB2LHI)



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