Larry -
First, confirm that the counter is fully warmed up and stable, preferably with a TCXO or other
better quality standard.
The hair dryer or bulb heat source is undesirable for just that reason. We don't want a HEAT
difference, just humidity with continuous temperature.
Then, turn on the receiver, wait about 5 minutes, and then measure each oscillator frequency. Then
wait another 30 minutes and measure each oscillator again. I'd then wait another 30 minutes and
measure again. If you have the patience, do it once more!! Try and disturb the receiver as little
as possible when going from soaking to measuring.
Compare for delta and direction on each oscillator and report back! :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Larry Mccabe wrote:
i agree re BFO..any thoughts on how to confirm which one is the culprit? was
thinking a heat source ..ie hair dryer ...or small light bulb,directed
independently at each might reveal some interesting results..
Larry WA0QHF
Sent from my iPhone
On Jan 5, 2012, at 2:59 PM, Garey Barrell<k4...@mindspring.com> wrote:
Larry -
That is interesting.... I've never experienced it, as my shack has always been
air conditioned. The PTO coil is pretty well sealed, and I wouldn't expect it
to be susceptible to humidity. The only other sources would be the BAND
oscillator, crystal controlled with a lacquered transformer, the 3rd Mixer LO,
also crystal controlled, and the BFO. The BFO is just an 'IF Can' style coil,
and would be the most likely suspect.
Would be interesting to see which of these oscillators is actually the one(s)
moving.!!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
Larry Mccabe wrote:
i've noticed some interesting drift characteristics on my r4c. i live in
florida.. shack in the garage.. during the summer months , with 80-90 deg temps
and high humidity, the r4c drifts approx 50 hz per hour. during the winter with
50-60 deg temps and reduced humidity the drift is reduced to 10 hz per hour .
in both cases these measurements were observed after a lengthy warm-up period
using a digital display counter. i have no internal fan or aux cooling in the
radio. only significant change in the vacinity of the pto is the sherwood audio
amp mod . temp and humidity obviously a significant factor in dealing with
drift. i know this is no big revelation.. thought the differences were
interesting though.
Larry WA0QHF
Sent from my iPhone
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