[Elecraft] [Fwd: Returned mail: see transcript for details]

[Martin AC6RM]

Does anyone know Jerry Henshaw's (KR5L, K2#0015) email address?  I'm
getting a bounce from bellsouth.net on the email address in his filter
alignment article.

tks es 73, Martin AC6RM




Jerry,

   I am submitting this to you and Wayne for review; it's based on your
article which I found most helpful.  I'd like to include it as an
addendum to the web page, if that's okay with you and Wayne.  Please
feel free to suggest or make modifications, or even kill the idea
(maybe I missed some other literature somewhere or something :)

   73, Martin AC6RM

   - - - - - - - - - -

   17 July 1999, KR5L (Jerry Henshaw, K2#0015) authored a most excellent
web page document entitled "Setting up your CW filters for the Tonally
Challenged."  It can be found on the Elecraft web site at the following
URL: http://www.elecraft.com/Apps/new_fil_docs/FilterSetUp.html.  I
used Jerry's methodology to adjust and center my CW filters in January
of 2003 after I had completed my basic K2 (#3021).  I was tempted at
first to employ the noise generator/software technique described
elsewhere on the Elecraft web site, but once I read and understood
Jerry's procedure, I have found no need to do so.

   Since Jerry's document was written, there have been some changes to the
firmware in the K2 -- one of which simplifies the adjustment procedure
even MORE than how Jerry's procedure outlines.  The HUGE difference is
that you now have direct access to the BFO frequency for adjustment and
display in the CAL FIL function.

   The real beauty of Jerry's procedure is that it makes it easy for one
to find the CENTER of the band pass.  It's precise enough that I was
able to achieve zero tonal difference between CW-Normal and CW-R once a
signal had been zero-beat with the SPOT command, and this makes a huge
difference in operating because flipping to CW-R can do a lot to make a
signal a lot more readable under certain conditions.  From an
operator's standpoint, CW-R is a good compromise for a lack of IF
SHIFT.

   With Jerry's permission, I'm submitting this addendum to his article,
so that we may have the benefit of the procedure he developed -- which
requires no special equipment or software -- given the firmware
updates.

   Here is the updated procedure:

1.  Ensure that the internal frequency counter probe is attached to TP2 on
the RF board.  Grab a piece of paper and a pencil -- you'll be doing some
simple arithmetic.

2.  Select the CW mode by tapping the MODE button until "c" is shown on
the right side of the display.  Select the filter you wish to tweek by
tapping the XFIL button.

3.  Select a clear frequency on the 40m band.  You want background noise,
but no carriers.

4.  The current pitch of the K2's CW side tone is important in the
arithmetic involved in centering your filter.  If you don't know what the
pitch of the side tone of your K2 is set to, check the setting now, by
tapping MENU and then tapping BAND+ until you see "St P  0.[nn]".  The
"0.[nn]" = is your current side tone pitch in kHz.  Make a note of it, and
then tap MENU again.

5.  Enter the filter calibration menu by tapping MENU, tapping BAND+ until
you see "CAL OFF", then hold the MENU button until the word "OFF" is
underlined by chevrons.  Then press BAND- until you see "CAL FIL."  Press
and hold the MENU button to activate the filter calibration.  You will see
"FL[n] [n.nn]c"  The first [n] = the filter number, the second [n.nn] is
the WIDTH of the filter in kHz.

5.  Change the width of the filter if you wish by using the VFO knob.

6.  Now tap DISPLAY.  This shows the BFO frequency.

7.  Find the BFO frequency for the CENTER of the bandpass by moving the
VFO dial until you hear the lowest noise pitch you can, and then reading
the frequency from the display.  To explain:  as you move the VFO dial
clock-wise and anti-clock-wise you will notice the pitch of the background
noise change -- one way makes it higher and the other way makes it lower. 
Move it in the direction that makes it LOWER.  There will be a point
where, as you continue to move the VFO dial, the pitch of the noise starts
to get HIGHER again.  GO BACK!  NAIL the point where it's at its lowest
pitch; rock back and forth on the VFO dial as necessary.  Increase the AF
gain to help you as necessary.  When you have found that low point, you've
found the center frequency.  Write down the frequency that is being
displayed.

8.  On your piece of paper, SUBTRACT the pitch of the CW side-tone
(obtained in step #4 above) FROM the BFO center frequency you just
obtained in step #7.  For example, if the BFO frequency you got in step #7
was 4914.17 and your CW side tone pitch is 0.70, then your new number
should be 4913.47. Move the VFO dial until this frequency is displayed. 
You will notice the pitch of the noise increase.

9.  Now, on your piece of paper, ADD the pitch of the CW side-tone
(obtained from step #4 above) TO the bandpass center frequency (obtained
from step #7 above).  For example, if the BFO center frequency you got in
step #7 was 4914.17, and your CW side tone pitch is 0.70, then your new
number should be 4914.87.

10.  Press and hold the CW RV button (note that this SAVES the setting
dialed up in step #8 above, as well as switching to CW-Reverse).  Now dial
in the number obtained in step #9 above.  Press and hold the CW RV button
again to save this setting.

11.  If you wish to tweek another filter, tap XFIL to reach the filter you
wisht to tweak.  Then do steps #5 through #10 on the new filter.

12.  When you are done tweaking filters, Tap MENU to exit the filter
settings.

13.  Test your filter settings by disconnecting the antenna and tuning in
the built-in signal at around 7000 kHz.  Zero-beat this tone using the
SPOT function (when tuned near the signal, press and hold TONE, then
adjust the VFO knob until you can't tell the two tones apart from each
other).  Select the filter you wish to test by tapping XFIL, and then
press and hold CW RV.  There should be no, or very little change to the
pitch of the tone you are hearing.  If there is a marked difference, then
the center frequency of the bandpass was not found closely enough in step
#7.  Redo from step #5 as necessary.

   One note: if there are any carriers in the band pass as you do step #7,
you can be easily thrown off; you need to get the lowest NOISE level
without carriers.

   For more detail on how this works, see Wayne Burdick's (N6KR) email
note of 11/30/1999 entitled "A detailed example of the mechanics behind
CAL FIL" at this URL:
http://www.elecraft.com/Apps/new_fil_docs/CAL_FIL_mechanics.htm.

   Once you understand how this works, tweeking your K2's passband will
become easy and understandable, and you'll be more apt to explore these
excellent filters when honing the K2 for a particular task.

   73 ES GL,

   Martin AC6RM






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