[Elecraft] [KX3] JT9 Drift Problem

[Jim Campbell]

I have a K2 that I have been using for almost a year on JT65. No 
problems whatsoever. I obtained WAS and eWAS in about 4 months of casual 
operating.

A few months ago I got a KX3 and for the last few days have been trying 
it out on JT9. I haven't been able to make a single contact. I would 
call CQ and see someone answer me on the same frequency but WSJT-X 
wouldn't produce a decode. I could answer a CQ and see a reply but again 
no decode. (I was running 5 watts.)

This afternoon I noticed something unusual. After a 1-minute 
transmission all of the received signals during the next minute had a 
skew (drift) and none decoded. The drift was for a total of about minus 
ten Hertz during the minute after the transmission. If I didn't transmit 
during the next one-minute cycle there was little drift and the received 
signals would decode.

I began to speculate that during the one minute transmission some 
temperature-sensitive component(s) heated up and caused a change in 
frequency. During the next minute they cooled and the frequency returned 
to normal. I played with this for a little while and the results were 
consistent. In the minute following a transmission there were no decodes 
but during all subsequent minutes signals would decode.

I switched back to the K2 and had five normal JT9 contacts, the nicest 
of which was John, ZD7JC on St. Helena Island in the South Atlantic. All 
this with a low dipole and 10 W. (He gave me a signal report of +00 
which meant that I could have been using one watt or less.)

I assembled the KX3 and believe that I ran all the tests and 
adjustments. Any suggestions as to what I can do to tame this 
temperature sensitivity?

73,

Jim - W4BQP
K2 #2268, KX3 #2875