[Elecraft] KX3: 6m Temp Comp Testing

[Edward R Cole]

I have completed the Temperature Compensation Procedure for the KX3 
on 6m.  Initially, I tried using the 5th harmonic of my 10-MHz OCXO 
since it is very accurate and stabile, but harmonic level was 
inadequate to run the temp comp procedure, so I used my XG3, 
instead.  I did run it a long time to stabilize the signal and 
constantly measured frequency on my counter.  Drift of the XG3 was 
less than 2-Hz over a couple hours of continuous running (ran off the 
same 14vdc PS as the KX3).

Before running the temp comp, Drift of the KX3 was 54-Hz upward 
running a test at 5w output on a sequence to duplicate conditions 
running JT65: 50-seconds key-down/70-seconds Rx, and repeated ten 
sequences (20-minutes total). Power was monitored on a Bird43 with 
25w termination.

After temp comp was complete the worst drifting occurred in the first 
ten seconds of the first sequence (+13 Hz).  After that there was no 
more than 10-Hz drift with the trend toward less drift as the test 
proceeded.  The last few sequences drift was +5 Hz.  I monitored Osc. 
Temp and PA temp with the KX3 display and Osc temp reached 54c at the 
end of 20-minutes running; PA temp was also 54c.  Osc. temp would 
drop slightly during the 70-second Rx portion of the sequence.  Temp 
compensation seems to work well to reduce frequency drift in 
transmit.  Rx frequency is within 1-Hz if not transmitting.

I did feel the KX3 body during the temp comp procedure and it was 
much warmer to touch once 52c was reached then the radio with heat 
sink runs after 20-minutes of JT65 simulation.  So I can say the heat 
sink is making a difference protecting the final 
transistors.  Internal heat still rises significantly so one needs to 
do the temp. comp. to reduce freq. drift.

details: http://www.kl7uw.com/KX3.htm

73, Ed - KL7UW
http://www.kl7uw.com
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