[Elecraft] K2/100 Frequency Stablity?

[Ron D'Eau Claire]

Recently I installed the PLL/BFO stabilization mod kit and measured the
stability of my K2. Its stability now is certainly better than many of
the initial reports; but the frequency still drifts more than 100 Hz
during a "typical" QSO. 

I tested my K2 on 15 meters as well as on 40 meters because the total
frequency drift is affected by the mixing scheme used in the K2. As Lou,
W7DZN, pointed out some months ago, the BFO and PLL Reference
oscillators tend to drift such that their errors will add on some bands
producing greater total drift and subtract on other bands to reduce the
total drift. He found that the drift was greatest on 15 meters. 

I found that my K2 changes frequency by over 100 Hz during a 10-minute
CW transmission on 15 meters. A subsequent test on 40 meters didn't show
much improvement. Even though the transmitter was already warm, having
run the 15 meter test a couple of hours earlier, the drift was still
close to 100 Hz during a 10 minute CW transmission. That was sending CW
as if in a rag-chew for 10 minutes with pauses now and then. The mixing
fan switched on about 3 minutes into the transmission and at the end of
the 10 minute period the heat sink was hot enough that I did not care to
press my hand onto it and leave it there any length of time.

These results have encouraged me to look into the stability issue more
closely. While I find that absolute "dial accuracy" is relatively
unimportant in a Ham rig, it's stability during a QSO is important to
me. 

I wonder if anyone else has done some real-world tests that might
indicate whether my K2/100 combination is typical? I see many reports of
K2's with "drift less than 20 Hz over several hours..." and have to
conclude that is in receive-only operation, especially if a 100 watt
amplifier is fitted to it. 


Ron AC7AC
K2 # 1289