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Old July 2nd 05, 02:25 AM
 
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Default R2000 SSB "improvement"

A friend is making some PCB boards for my
AD607 synch detector project so I tried
something else.

Today was a REAL slow day at work. Someone
had to be thre "just in case", and as new
man I was bitten. So I took my original R2000
in to try an idea I hade for a while.

The product detector isn't the best design.
It uses a transformer to couple the IF to
the mixer bridge and a set of resistors to
couple the BFO. El stinkero.

I cut the traces and put a minicircuit 1:1,
secondary CT, between T18, removed the BFO
feed resistors and fed the BFO to the center
tap. I replaced the 1N60, (which where far
from matched!) with some old HP hot carrier
diodes (HP2800). The differnce between this
uit and a stock unit was night and day.

Very tedius work. But very worthwhile.

I have both radios complete, I ended up
staying an extra hour to complete this and
a rather plain "improved AM detector".

Before I reported that when I biased the AM
detector diode I experienced some very odd
happenings. I don't know what I did wrong,
but when I re did the experiment, it offered
a slight improvement. The AGC has it's own
detector. Just for grins I tried a hot carrier
and low voltage Shotky (zero bias) diodes.
They both worked but really wasn't enough to
bother with . The diode needs a negative bias
voltage and that is a big hassle.

Even though I have NO plans of ever taking
either R2000 out in the field again, I decided
to go on and add both these mods because they
are very worth the "minor" efforts. And for
this weekend I don't have my fancy synch detector.

Terry