[R-390] calibration osc

[Tim Shoppa]

>  My calibration oscillator (1963 Imperial) puts out two carriers several 
> hundred cycles apart. One is weaker than the other. It is almost as if the 
> multivibrator is not phase locked to the main xtal oscillator. Both carriers 
> are stable, and I have zeroed the stronger carrier to wwv. It is not a 
> serious problem, but I would like to fix it next time I have the rf deck 
> out. Any ideas?  Thanks.....Steve....N8YE

My suspicion would be the crystal itself.  Crystals with mechanical damage
and/or poor mountings and/or high ESR's can show spurs like what you're seeing.

I'm not so sure "phase lock" is the right term, I thought it was just a
divide-by-two-flip-flop made out of a 12AU7 to get from 200kHz to 100kHz and
make lotsa harmonics.  (Yep, digital electronics in our beloved R-390A's!)

Is the spur always a few hundred Hz away?  If so, I don't think it's the
calibration oscillator.  If it were the calibrator and it was 200 cps at 10MC, then
it would be 20 cps at 1MC and 600 cps at 30MC.

One of my RF decks had several resistors in the calibrator section
way out of tolerance (like 50-100%) and discolored by heat.  I think
it was the flip-flop parts.  Strangely enough they seemed to track each other
exactly (i.e. if one 10K resistor was now 18K, the other was 18K too, and
the 1M was now 1.8M!  There's gotta be some deep meaning there...)

Tim.