K2 BFO Drift / Filter Alignment

Posted by Douglas Furton on Dec 31, 2009; 2:00pm
URL: http://elecraft.85.s1.nabble.com/K2-BFO-Drift-Filter-Alignment-tp4236424.html

I'm having a problem with my K2 (SN 6761 10W/CW only): I have to align the crystal filters almost daily.  It seems the BFO shifts by 200 Hz or more almost daily.

This may have been covered in the reflector at various times, but I've not seen this exact problem described, so I've decided to go ahead and post a note again to get a fresh opinion.

I'll align the filters with noise in the band-pass using "Spectran" and all is good for the day.  The next day, the filters are all out of alignment -- say 200 Hz low.  The filters are all low by that amount.  So, I realign the filters, all is good, until it happens again.  Next time, the filters will all be maybe 200 Hz high.  The realignment amounts to shifting the BFO 1-3 steps using cal fil.  And, again, all the filters shift by about the same amount.

I see what I would call *normal* BFO drift with warm up, but not enough drift to cause the filters to change by as much as 200 Hz.  The ambient temperature is about 65F and doesn't change all that much from day to day.

Any suggestions?

Doug
K8EXB

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