[Elecraft] Calibrating K2 Xtal Filters

[Earl W Cunningham]

For Bill, W4ZV:

You should *not* use a signal to adjust CAL FIL on the K2 because it
makes an easy job difficult and confusing.  You can use band noise on
160m (best for this method because it is the noisiest band), but now with
the summer thunderstorm season rapidly approaching it won't be possible
to get steady band noise, so a noise generator is the best choice.

Using noise and Spectrogram makes the job very easy.  Just use CAL FIL to
adjust each of the 8 CW filters (4 for CW and 4 for CWN) so that the
center of each filter passband is centered on 400 Hz (your sidetone
choice) using Spectrogram.

I find that setting up the narrowest filter first works out best.  Then
set up the next-to-narrowest filter, etc.  After setting all of the
filters up, then if , when switching filters, you hear a slight change in
the pitch of received CW signal, you can tweak CAL FIL for the three
widest filters slightly so that there is no change in the received pitch
when switching bandwidths.  The signal will still be very close to being
centered in the passbands of the wider filters - that's why I set up the
narrowest filter first, centered exactly at 400 Hz.

This method automatically takes care of the received CW signal not
changing pitch when you switch sidebands, i.e., between CW and CWN (as
long as the received signal is tuned to your sidetone pitch).

I have the xtal filters in my K2 set to 1000, 400, 100 and 50 Hz.  Ditto
for the KDSP2 filters (you know me -- I like ultra narrow BWs for getting
better S/N on 160m).

It's an enlightening experience to use Spectrogram to look at the filter
passbands of your other radios also.

73, de Earl, K6SE