Folks :
A little while back I mentioned on this list that I felt that I was
having some frequency
drift issues with my K1 since I had changed the VFO tuning range from
wide to
narrow. I decided today that it was time to see if I could do something
about it,
but I figured that I needed to quantify the magnitude of the drifting
first otherwise
I wouldn't know whether I have made things better or worse.
I hooked my K1 up to a well regulated 13.8 V supply, turned it on, tuned
it to 7.040 MHZ, started a timer and let it be. Note that the rig was
inside the
air-conditioned house at a temperature of 24c and not subject to any
vibration.
Here is what I observed
time: 5 min total drift: -200hz (freq 7039.8 mhz)
time: 30 min total drift: -300hz (freq 7039.7 mhz)
time: 60 min total drift: -300hz (freq 7039.7 mhz)
So it appears that I am getting approximately 300hz drift down in
frequency
in the first 30 minutes and then things stabilize.
I checked the Specs in the front of the manual and it says < 200 hz /
hour after a 5
minute warm up at 25 degrees C so I guess that technically things are
within spec
as I am seeing only about an additional 100hz drift within the first
hour, after the initial
5 minute warm up.
It is likely that the drift is greater in a less controlled
environment, especially outside with the
brutal heat we have been having here this summer.
I'm still wondering if replacing C2 (68pf disc cap) with a polystyrene
or even
an NP0 cap might make things a bit more stable when using the rig in
the field.
Does anyone think that this is worth doing? Comments?
Michael VE3WMB
P.S. Someday I would love to see an upgraded K1 (lets call it K1.5)
with a
DDS vfo like the KX1 and a continuously variable IF filter bandwidth
like the KX1
or the ABX on the Sierra.
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