Mark,
How did you set the BFO frequencies? What measuring device did you use?
And what frequency reference is it based on? Some sort of counter with a
built in reference oscillator? How do you know it is accurate?
How are you determining that the USB and LSB transmit signals are so
different? Listening with some other receiver? I would suggest that you
listen with a receiver that has a really wide IF filter, such as the 15
kHz filter used for AM or narrow band FM. And listen in either DSB mode,
or AM mode with a BFO turned on. This is to avoid having differences in
the receiver's LSB/USB performance from making you think your
transmitter has a problem. The problem could be incorrect BFO
frequencies and/or non symmetrical filter in the receiver.
You might try bypassing the 2.4 kHz filter altogether for a test. Then
you will be generating a DSB signal, which should sound identical on
either sideband. (I am not sure how much attenuation there is in that
filter, so there is the possibility of over driving the the first stage
after the filter, but turning down the mic gain should compensate. I
also don't know whether DC continuity through this path would cause
trouble, so if you bypass the filter you should do it with a capacitor
and not just a wire jumper. You may want to try listening directly to
the 9 MHz IF signal before it gets heterodyne converted to whatever band
you are operating on.
I set the reference oscillator, and adjusted the passband tuning
frequencies.
Should only affect receive performance, transmit IF does not go through
PBT board.
I even tried replacing the 9mHz 2.4 filter, to no avail, same situation.
Try bypassing as described above.
(I was actually hoping there was an adjustment to center the sidebands
in the balanced modulator loop,
I don't know what you mean by this.
I dont twirl slugs or caps just to "see" what will happen, ha ha ha)
A good philosophy.
DE N6KB
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