[Elecraft] New to me K2 question. Filter performance

[Tom Hammond]

Hi John:

>My question revolves around the filter performance. My rig has the 
>aftermarket filter option. Here's the scenario:
>
>Mode: CW
>Band: any (have tried 40 and 20)
>XIT off
>RIT off
>
>I tune a CW signal in, with the filter selection to FL1 (which is OPT1), 
>and adjust main tuning to comfortable pitch.
>
>If I then select FL2, 3 or 4, the signal disappears from the passband and 
>is found some distance away. Toggling between 2,3 and 4 makes no 
>difference in the pitch or the position of the signal in the increasingly 
>narrow passbands...in my rig 700 400 and 200 hz.
>
>Here's some data.
>
>Signal tuned w/OPT1 filter      14.04403 Mhz
>Same signal w/FL1-FL3 filters   14.04272 Mhz
>
>on 40m
>
>Signal tune with OPT1 filter       7.0432 Mhz
>Same sig tuned w/FL1-FL3 filters   7.0421 Mhz.

Though I can't believe that Gary made such an alignment error, it would 
almost appear that the FL1 BFO may have been set to the wrong side of the 
filter passband... at least for your CW Norm selection.

Question: Does this same scenario occur in the CW REV mode?

>My question is, will the filter alignment process resolve this issue?

ABSOLUTELY! This should NEVER be a problem.

>Should I delve into the filter alignment process? I'm confident in doing 
>so, I just want to make sure I get the "golden screwdriver" applied to the 
>correct fix!  :-)

Certainly!

Using Spectrogram to (re)align your CW filters is a snap!!!

If you don't mind, please send me a reply, giving me the BFO frequencies 
currently used by your CW Norm and CW Rev filters, for all FLx settings. To 
do this...

(typing this from memory, so I hope I don't miss a step)

  1) Open K2 and install the FCTR probe between the
     Control board jack and TP2 (thru hole in middle
     of the SSB adapter).
  2) Replace top cover and allow rig to warm up a bit
  3) Select 40M
  4) Select CW Normal mode
  5) Select FL1
  6) Press MENU
  7) Use VFO knob to scroll to CAL
  8) Press-Hold MENU to underline CAL
  9) Use VFO knob to scroll to FIL

     DO NOT TOUCH THE VFO KNOB FROM NOW ON!!!

10) Press-Hold MENU to begin filter alignment
11) Press BAND- to display the BFO frequency
12) Record the BFO frequency for FL1
13) Press XFIL once to move to FL2 and repeat step 12.
14) Repeat steps 13 and 12 for FL3 and FL4.
15) Press-Hold CW-RV to switch to CW Reverse mode
16) Press XFIL to return to FL1 and then repeat steps
     12 thru 14, recording all BFO settings for the CW RV
     mode.

Once finished with the steps above, determine the (approximate) center 
frequency of your CW filter:

  1) Press-hold CW RV to return to the CW Normal
     mode.
  2) If necessary, press XFIL to select FL1.
  3) While listening to the background noise from
     the K2 speaker, tune the VFO knob until you hear
     the lowest-frequency background noise from the
     speaker. It should rise in tone on either side of
     the filter center frequency.
  4) Record the frequency of your filter's center
     frequency.
  5) Now, before you do anything further, REMOVE the
     FCTR probe from TP2. This allows you to exit from
     CAL FIL mode WITHOUT the K2 trying to save any
     changes you might have made to the settings. Since
     it can't read the BFO frequency any more, it will
     fail in it's attempt to save changes.
  6) Press-Hold MENU to exit from the CAL FIL menu.

Now, take a look at the recorded BFO frequencies and compare them to the 
BFO center frequency. For each mode (CW Norm or CW Rev) ALL of the BFO 
frequencies for each mode should be either ABOVE or BELOW the BFO center 
frequency, but they should not jump back and forth within a the mode. If 
they do, then one or more of the settings is wrong. In this case, re-run 
the Spectrogram procedure for setting your CW filters.