CAL FIL question on K2 #4565

[BobConvers]

I completed assembly of #4565 and all seemed well.   I used Spectrogram to
perform CAL FIL using the N0SS article as a guide, but chose 650Hz as my
sidetone freq since I thought I preferred a slightly higher tone, and selected 100Hz
as FIL4 bandwidth.   I completed the CAL FIL process, with all values of the
BFO parameter and BFO freq consistent with (not quite identical to) the manual.
 

After tuning around the bands for a while (and having a ball!), I decided
that the sidetone freq was too high and 600 Hz was probably what I wanted, after
all.   So I selected 600 as the sidetone and tried to re-do CAL FIL.   CW
NORMAL went well, and I got slightly different values than for 650 Hz, as
expected.   Most of CW REVERSE seemed OK also - except for FIL1 and FIL4.   For FIL1,
the BFO parameter was EXACTLY the same as for CW NORMAL, and for FIL4 the BFO
parameter was the same as the bandwidth center value.   Specifically, here is
what I found:

Using band noise at 10.115 since it was quieter than other bands on a
Saturday morning, I found the BFO parameter at center of bandwidth (lowest tone of
background noise) to be about 151 (same as on the previous 650Hz run).   Here
are the BFO parameters for the four filters on CW NORMAL and CW reverse:

CW NORMAL    -     FIL1: 122;   FIL2:114; FIL3: 112; FIL4: 110

CW REVERSE -     FIL1: 122;   FIL2: 155; FIL3: 153;   FIL4: 151

I understand that all BFO parameter values for CW REVERSE should be ABOVE
bandwidth center (151). The only possible complicating factor I noted was that
occasional signals could be heard (actually seen) on the band, manifesting
themselves as spikes on the Spectrogram display. Actually, it was one of these that
leads me to believe that I was properly getting a reverse display between CW
NORMAL and REVERSE, since one spike appeared at the right edge of the
Spectrogram display on NORMAL and at an equal distance from the left edge on REVERSE.

I would appreciate suggestions on what 's happening.

73,
Bob, WO3E
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[Ron D'Eau Claire-2]

Bob, WO3E wrote:

 So I selected 600 as the sidetone and tried to re-do CAL FIL.   CW
NORMAL went well, and I got slightly different values than for 650 Hz, as
expected.   Most of CW REVERSE seemed OK also - except for FIL1 and FIL4.
For FIL1,
the BFO parameter was EXACTLY the same as for CW NORMAL, and for FIL4 the
BFO
parameter was the same as the bandwidth center value.  

Reply: ------------------------------

If you've got the same BFO setting for CW N and CW R on any filter, it's
certain you are listening on the same sideband in both cases!

One way to test which side of the bandpass your BFO is set on is by noting
how the beat changes as you tune. On 40 and below, the beat note produced by
a signal will decrease as you tune *down* in frequency in CW N and as you
tune *up* in frequency in CW R. If that doesn't happen in each filter
position, you have one of the BFO frequencies on the wrong side of the
bandpass.

The BFO settings also affect the local oscillator frequencies as well.
There's a good description of how they interact on the Elecraft web site in
a paper called "The Mechanics Behind CAL FIL".

Ron AC7AC



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[BobConvers]

Thanks, Ron.   I did indeed have the BFO for FIL1 on CW-R on the wrong side.  
 I cranked the BFO parameter up toward the center value and beyond, and saw
another bandpass display (the right one) on Spectrogram.   I had not
appreciated that you will get a similar display on either side of the bandpass center.  
It's all starting to come together now.

All I have to do now is get resonant antenna up (or build the KAT2) and have
the first QSO.

73,
Bob, WO3E
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