"Dale Parfitt" wrote in message
...

"Richard Knoppow" wrote in message
m...


My R4-B is similar. Following the instructions gets it usable but
certainly not symmetrical. I have not yet gotten at this in depth partly
because I don't have a sweep oscillator and I think one is probably
necessary to tune this thing properly.
If you don't know the history of your RX (meaning bought it new) its
quite possible someone else tried tuning it. Also, perhaps there was a
little mechanical drift in the permeability tuned coils. I wish there
was
more service information available for Drake stuff. I am about to
undertake fixing what I _think_ is a problem in the balanced modulator
of
a T-4XB, acts like there may be a bad diode. There is a Drake mailing
list. I joined it but after getting a confirming message there has been
no
traffic whatever.

Hi Richard,
Join the Drakeradio Yahoo group- active and a lot of knowledge.
You may be able to use Spectrogram 16 to characterize your filter. Disable
the AGC, no antenna, adjust the AF Gain for a usable trace, and run
Spectrogram 16 in the peak hold mode- after several minutes, you'll have a
nice plot of the filter characteristics.

Dale W4OP

Extremely minor variations can cause this. It is best to sweep the filter
then offset the tunable oscillators to bring things into line. Less than
100 Hz will have a great effect on the apparent noise between upper and
lower sideband. I would be more concerned with breaking the filter, since
you can't just replace it. The passband is variable.