[Elecraft] N0SS CW Filter Alignment

Wed Jun 5 23:31:00 2002

The K2 has 10 hZ steps thus it is almost impossible to get it exactly.
After about 10 iterations I was able to achieve the following after
getting WWV within 10 hZ.

On lower bands (below the reversal of BFO shift) got the following
results reading the frequency off of the MIXW 2 display.  (Seems to
provide a finer resolution than Spectrogram.)

	FL1	FL2	FL3	FL4

USB   REF	-4	-6	-10
LSB	REF	0.0	0.0	0.0
CW	REF	-5	-5	-5
CWR	REF	-7	-7	-7

USB, CW, and CWR all seem to provide absolutely no change in pitch
(Using 750 Hz) Listening to a steady carrier on the air with RF gain and
ATT set so that it is just audible and at normal listing level.  Will
probably play some more over the weekend (After I write down all the
numbers.) and see if it possible to get closer.

Messing around with PSK, It looks to me as there is no reason not to use
LSB (on the lower bands), especially if you intend on dropping to a
narrow filter.  

Tom, N0SS provided this in an earlier message

I have found that you can get the shift reduced to less than 1 Hz by
just
repeating the procedure numerous times. Sometimes by just adjusting one 
filter at a time.  Often I just go in to the procedure and just the BFO
by 
one 'notch' and back again and exit, so it will recalculate the offset.
I 
have been able to get it down to the point where there is no audible
pitch 
change (musicians ear) between the filter settings, and just a slight 
phase twist on the PSK tuning eye.

It WILL drive you nuts, but it can be much better than 10 - 20 Hz.

I have found that if you change the cap adjusting the frequency, that
you need to 1) change the filter (even if back to the same setting) and
then 2) re run Call-PLL.   I found that when I got close to the proper
alignment with WVV, that I needed to use on half of the calculated value
for changing the cap.   Remember, Only adjust LSB for WWV, the BFO shift
will fix the other.  Look at the "crystal and BFO settings" section of
the manual.

Let the rig set for about four hours before starting, and put the cover
back on quickly after any adjustment.

Don't set BFO/filters until happy with WWV alignment.  If changed you
start from scratch.

Rich

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Ron D'Eau Claire
Sent: Wednesday, June 05, 2002 9:25 PM
To: [email protected]
Subject: Re: [Elecraft] N0SS CW Filter Alignment 

> I noticed that the 500 & 600
> hz tone markers don't line up exactly with the respective marks on the
> Spectrogram when I shift from usb to lsb or (cw & cw reverse) . In
other
> words, if I put the tone on 500 hz on lower sideband then shift the K2
to
> upper sideband it is sort of close to 500 hz, if I try I can't get
both on
> 500 hz . For instance on 10 mhz lower sidband displays 999982 & upper
> displays 999977.
> Ron N8SZY

As far as I can see, that is entirely "normal" for a K2. The i-f filter
is
NOT symmetrical. That means that the slope of the lower frequency side
of
the bandpass is NOT the same when shifting from upper to lower sideband.

If I set the filters to produce the same response on a DSB AM signal
when
switching from upper to lower sideband, the BFO is way off from the
right
setting for good signal quality. Indeed, I am rather disappointed in the
gradual slope on the lower sideband in any case. It produces fairly
"muddy"
sounding audio compared to the upper sideband. Optimizing the BFO
settings
to minimize this means that I must retune slightly when shifting between
upper and lower sideband. That's not an issue for me, since I don't
normally
listen to double-sideband signals, Hi!

Ron AC7AC
K2 # 1289

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