[Elecraft] K2 Frequency Stability

[Unifiedtx@aol.com]

John Grebenkemper, KI6WX, has recognized the need for better frequency 
stability and has made modifications to reduce frequency drift.  He has asked 
others about their K2 drift rates.  I have not heard about his findings, but 
I would not be surprised if all K2s have a slow drift rate of from 130Hz to 
170Hz over a period of 8 to 12 hours with an ambient temperature of 60 to 68 
degrees F.  This drift is considerably greater than most of the late model 
commercial American and Japanese made transceivers.  I have also noticed that 
the VFO range tends to shift depending on whether the bale is retracted or 
down.  It may be that the bale in the retracted position is pushing against 
the cabnet bottom plate causing a change in L33 parameters.  With the bale 
down the cabnet bottom may be further away from L33.  During construction I 
carefully positioned L33 tightly in the grommet and pulled L33 leads tightly 
into the PCB during the soldering process.  I made a check of the proximity 
of L33 to the cabnet bottom plate by removing a side panel and observed the 
clearance.  The clearance does not seem to be a problem.
I would like to know if anyone else has notices this subtle frequency 
difference.  It can only be noticed by looking at the drift from a cold start 
to the point of no apparent further drift.  I also would like to know if 
anyone has come up with a way (perhaps change in components) to substantially 
reduce this drift.  John Grebenkemper was able to cut his drift from 155Hz to 
65Hz.  His mod, however, is not for the faint of heart and appears to be 
quite involved.
Roy Morris  W4WFB