[Elecraft] Problems because of filter switch during CW operation K2/ Filter FL4

[Renardy, Martin]

Dear all,

I ran through the K2 filter aligment considering all your tipps and
tricks. I also adjuest the reference oscillator 
on the control board again. My filter bandwidths are 1.5 kHz, 700 Hz,
500 Hz and 200 Hz (Filter FL1 to FL4).

I have used Spectrogram to align the filters. The settings are matching
with zero beat tests on a carrier.

Now Fliter FL1 to FL3 are working perfectly. I can switch through the
filters and the tuned signal stays with
maximum amplitude in the filter with minimum frequency change.

The strange thing: Filter FL4 was not working. So I have set it's
bandwidth to 2 kHz and analysed the passband
By tuning over a carrier observing the peak in spectogram. I have seen,
that the center frequency of FL4
is different from FL1 to FL3!

How can that be, because the Filter settings FL1 to FL4 are controlling
the same electrical filter?!?

Regards

Martin