Argosy VFO Drift
Mon, 27 May 96 11:31:49 -700
After 30 min warm-up,my current Argosy drifted +500hz in the
next 1/2 hr.
This positive change indicated an effective decrease in
capacitance due to heat build up.
The test was done in an remote room of my basement where temp
is constant and there are no circulating air currents.
After several days of experimenting, I found the following
I removed C32 (150pf n080) from the vfo board in the inside of
the vfo box and replaced it on the foil side of the VFO pcb
with a 150 pf np0 capacitor.This "zero "drift capacitor did
After an over nite cool off a check of drift excursion shows
+/- 20hz in the 1 st hr from a cold start and then at -20 hz
over the following 1 hr period.
Anyone wishing to improve the drift characteristics of their
rig should ensure that they are testing in a stable environment
and remove the S-Meter bulb from the set before attempting to
measure frequency drift.(The bulb generates heat). The frequency
readout in the stock Argosy is not accurate enough to measure
drift as it does not have enough digits. A separate frequency
counter must be used and allowed to stabalize its own drift
for some time before the test.
JIM VE3DDY email@example.com