[Elecraft] K3 Front Panel Temps/freq drift

[Brian Alsop]

Guys,

I'm curious what is the max front panel temp you're seeing after a 
period of operating with significant transmit time?  Also what is the 
room temp at this value.

The reason I ask has to do with the K3 Master Oscillator calibration 
procedure and later drift.  A detailed set of measurements with a stock 
K3 indicates a good correlation of drift with front panel temperature. 
With the standard oscillator, measurements indicate that the K3 drifts 
about -1.2 Hz/C (.12ppm/C) degree at 10 MHz.  Here a Rb 10MHz secondary 
frequency standard was used as well as a counter to measure how the 
audio tone changes vs time. This allows sub Hz changes to be observed.

Normally one does the calibration receive only.  In that case with an 
ambient temp of 24C here, the front panel temp rises 34 C after 90 
minutes.  I normally calibrate after such a warmup.

If the front panel temp rises another 10C after periods of transmit, the 
frequency could be off by about -12 Hz at 10 MHz (-60 Hz at 50 MHz). 
Sure that's not a lot. But it says, perhaps one shouldn't knock 
themselves off trying to be super accurate with the calibration.  There 
will be another couple or perhaps as much another 10 Hz (1ppm) error due 
to transmiter heat buildup.  The actual amount can probably never be 
predicted.

It is clear to me if one "needs" more accuracy, the high precision 
oscillator option and/or locking to an external reference would be needed.

I'd love to look at the high stability oscillator drift as well. 
However, satisfying that curiosity for $100 isn't going to happen.
Perhaps someone out there with the high stability oscillator could 
repeat the above measurements and report the results.

73 de Brian/K3KO





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