[Elecraft] K2 Frequency stability

[adamkern at uchicago.edu]

Hello again and happy holidays!

With regard to the K2 frequency stability...

Several good points were raised and I realized that I wasn't 
adequately specific before.  The drift I notice is primarily 
related to warmup and not during normal operation.  I will 
perform the aforementioned test to confirm whether the 
instability is primarily in the BFO or PLL oscillator.  
However, the biggest drift occurs after the rig warms up.  
Heavy CW operating with the KPA100 brings the temperature 
very high and this large increase in temp is necessary to 
make the rig drift in frequency any more.

Of course, the distinction between warmup and operating 
drift becomes academic if one turns on the rig from a "cold" 
start and start operating heavily right away. :)

More commonly, I find that I operate outdoors or somewhere 
where ambient temperature is cold, run CW at 100 watts and 
then drift somewhat shortly after the "cold start".  Again, 
I suspect that this is due to "warmup" drift and not some 
large drift attributable to a malfunctioning temp-
compensated PLL.

On average, from 60 F to warmup the freq at which I zero 
beat WWV drifts down an extremely predictable 50 Hz.  From 
normal operating temp to high temp (e.g. 100W CW operation 
sufficient to kick the KPA100 fan to high) the WWV zero beat 
frequency will move another 20-30 Hz, for a grand total of 
80 Hz relative to a "cold start".  There is never any 
unpredictable change in zero beat frequency beyond this.  
Once the rig reaches full operating temperature the drift is 
never greater than 10 Hz.

So it seems that the rig is operating within spec and I have 
nothing to worry about, save to calibrate things so that the 
radio zero beats WWV at operating temperature.  I will 
confirm this by running the test to differentiate between 
PLL and BFO drift.  Correct?

Happy holidays!

Adam, N1KO