[R-390] VFO Heater Questions

[David Wise]

I don't know how much of the R-390 VFO oven design
was carried over to the R-390A (It's not discussed
in the Cost Reduction Report), but the R-390 Final
Engineering Report suggests on page 71 that the oven
runs at 70 degrees C.  As Bob Bethman mentioned, it,
and the second oscillator's crystal oven, run only
when the OVENS switch is on.  This is not recommended
for normal use due to reduction in component life.
The only always-on oven is the one containing the
calibrator crystal and the 17MHz first oscillator
crystal.  The BFO is unheated.

FWIW,
Dave Wise