[Elecraft] Filter question

[Julian, G4ILO]

You may almost fix it, or you may end up tearing your hair out...

I believe the problem is actually because both the BFO controller and the 
VFO have limited frequency resolution (in the order of 10Hz.) The K2 
firmware has to shift the frequency of both of them in order to get the 
frequency correct with the filter centered at the desired part of the 
passband. Sometimes the errors cancel out, other times they may add. So you 
may spend a lot of time trying to eliminate the frequency shift on one spot 
frequency, and then find it's back again on another one.

I've learned to live with it - it's easier!

73,
--
Julian, G4ILO. (RSGB, ARRL, G-QRP, K2 #392)
G4ILO's Shack: http://www.qsl.net/g4ilo

"David A. Belsley" <belsley at bc.edu> wrote:

Stan:
This behavior is typical. I don't have actual figures, but I would bet that 
the majority of K2s display this issue. It is not really a problem, and 
there is a sense in which you can't get rid of it. You might be able to get 
it to behave for a while, but in time it will return. It has to do with the 
fact that the K2's frequency resolution is only within 10-20 Hz, so what 
you are hearing is within spec.

You might try the following to see if it clears up, at least for a while. 
After you get your BFO settings correct (i.e., the sidetone is placed in 
the center -- or high spot -- of the filter), go through all the filters, 
one after the next, resetting each as noted below. Use the index (numbered) 
settings rather than the frequency settings. Move each number one or two 
numbers, say, lower, and then back to the original number. Move to the next 
filter, do the same through all the filters. Do this for both c and c-bar. 
You may now (possibly) have the same tone when switching through the 
filters, at least if you are listening to a note that is at you chosen 
sidetone.

If that works (and it does for me), great. But a few weeks from now, you'll 
notice that one of the settings will be off by 10Hz again. At this point, I 
just live with it. If you don't worry about it, you'll find that it is 
really a non issue.

best wishes,

dave belsley, w1euy