[Elecraft] Filter Alignment Using Spectrogram

[k6se@juno.com]

I've found that the best way to set up the xtal filters in the K2 using
Spectrogram is a follows:

1) Allow your K2 to warm up for about an hour to alleviate the BFO
frequency drift problem.  The internal frequency counter probe must be in
TP2 for this procedure.

2)  For CW, set up Spectrogram to display from 0 to 1500 Hz and set up a
marker at the frequency you have your K2's sidetone pitch set at.

2a) For SSB, set up Spectrogram to display from 0 to 2750 Hz and set up
markers at 500 Hz and 2400 Hz.

3) Disconnect the antenna from the K2, turn the preamp on, and use only
background noise while adjusting the filter passband displays in
Spectrogram. 

4) Set up the filter bandwidths that you want for both CW and SSB using
CAL FIL.

5) While in CAL FIL, tap BAND-.

6) Turn the K2's VFO knob so that each individual passband for all SSB
filters is centered evenly between the 500 and 2400 Hz markers you set up
in step 2a above.  Do this for both LSB and USB (8 adjustments).  This
completes the SSB filter setup.

6a) Turn the K2's VFO knob to center the passband display for each filter
passband on Spectrogram at the marker you set up in step 2 above.  For CW
bandwidths greater than 0.70 kHz, set the lower frequency part of the
passband at the marker.  Do this for both CW normal and CW reverse (total
of eight filter bandwidths).

7) Select the narrowest CW filter bandwidth you set up in step 4 above.

8) Temporarily exit the menu.  In CW mode, tune in the "birdie" on 7000
kHz so that its pitch is the same as your sidetone pitch.

9) Re-enter CAL FIL and tap BAND-.

10) On Spectrogram, you should see the 7000 kHz signal peaked  at the
marker you set up in step 2 above.  This is your reference point, so DO
NOT adjust the BFO at this narrowest filter setting.

11) Tap XFIL to select the 2nd narrowest CW filter.  If necessary, adjust
the BFO by turning the VFO knob to center the 7000 kHz signal at the
marker.

12) Repeat step 11 for the remaining two CW filter bandwidths.

13) Repeat steps 7, 10, 11, and 12 for all four filter bandwidths on the
other CW sideband (CW normal or CW reverse).

14) Move the internal frequency couinter probe to TP1 and execute the CAL
PLL procedure.  (You should already have set C22 on the control board so
that the 4 MHz xtal oscillator is exactly at 4000.0000 kHz prior to this
procedure).
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If you use the above procedure, you'll hear little (if any) change in
pitch of a CW signal as you step through all CW filter bandwidths for
both CW normal and CW reverse.  If the received signal's pitch is set to
your sidetone pitch, you should hear no difference in the received
signal's pitch when you switch between CW normal and CW reverse.

Contrary to other procedures posted, my procedure sets up the narrowest
CW filter first and uses this as a "reference".  You'll have much less
trouble getting the pitch of received signals to remain the same for all
filter bamndwidths if you do it this way (i.e., narrowest first).

If you have the KAF2 option installed,  it's very easy to adjust AF1 and
AF2 using Spectrogram and the 7000 kHz "birdie".  Just tune in the
"birdie" so that its pitch matches your sidetone  pitch, select AF2 by
HOLDing XFIL/AFIL twice, and adjust both R1 and R2 on the KAF2 for max
signal at the sidetone pitch marker on the Spectrogram display.

73, de Earl, K6SE
68 countries with K2 #2622 and counting.....