Hello, all
I've been bothered with the CW tone/filter setting
on my K2 for some time now. I seem to need to run
CAL FIL daily, at least to have the BFO freq. read
into memory. I observe that the CW tone starts low
and drifts upwards as the rig warms up when I tune a
signal to the center of the filters (maxing the
S-meter).
Here is some data characterizing the freq. drift
in my K2 (#6761). I measured the PLL and BFO freqs
with a nice frequency counter. I measured these
shifts with the K2 locked at 7050 kHz, and computed
the total shift = dPLL - dBFO (all referred back to
the initial (T=18.5C) measurements. I measured the
temp. with a thermocouple in contact with the PLL
thermistor board. I also measured the PLL and BFO
control voltages at various times and found them
to be constant.
Cumulative freq. Shifts
T PLL BFO Total
(C) (Hz) (Hz) (Hz)
18.5 0 0 0
19.3 9 -17 26
19.6 13 -34 47
20.2 17 -57 74
20.8 19 -70 89
21.3 24 -79 103
21.6 26 -87 113
22.0 28 -92 120
23.3 37 -124 161
24.0 40 -136 176
24.5 46 -164 210
25.0 53 -205 258
25.5 62 -256 318
25.5 70 -310 380
(I hope the table above remains tabulated
properly. Best viewed with a monospace
font.)
It seems the thermistor board compensates the PLL
fairly well (although maybe I could tweak RA upwards
a bit), but the BFO drifts considerably, and
since the PLL and BFO drift in opposite directions,
the total drift is exaggerated.
I may measure the drift on a second band, but these
data are just from 40 m.
I would really like to improve the temp. stability
of my K2.
Does anyone have any suggestions?
Thanks,
Doug Furton
K8EXB
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