[Elecraft] Frequency shift [was: A couple of questions]

[Julian (G4ILO)]

Hi Don,

It's true I'm not the most patient person on the planet but it seemed to me
that eliminating the frequency shift between different filters was nigh-on
impossible. I spent a lot of time on it and I seemed to be going round in
circles and never completely getting rid of it.

It seemed to me that how successful you were at eliminating the shift
depended on exactly what voltage was needed to shift the BFO and VFO to the
right frequency, and how close that was to the values that the K2 could
store in its registers, given their limited resolution. Because of that, I
concluded that whether one could eliminate the shift or not was a matter of
luck, dependent on the K2 in question; if you are out of luck, the best you
can hope to do with the shift is minimize it.

I didn't notice a VFO mod listed on the mod kits page, btw.

73,
--
Julian, G4ILO. (RSGB, ARRL, K2 #392)
Homepage: http://www.qsl.net/g4ilo



  ==== Original message ====

> Hi
> 
> If you are getting a frequency shift of the CW tone when the bandwidth 
> is changed then the problem is most likely the alignment of the filters. 
> The BFO mod vastly improves the drift with temperature of the filters 
> but you can still have the frequency shift if the filters are not set up 
> right..  
> 
> I would go back over the filter setup with Spectrogram for now but in my 
> opinion the VFO and BFO mods are a must do for all K2's with a serial 
> numbers under 3000.  
> 
> Don Brown
> KD5NDB