Problems because of filter switch during CW operation K2

[Renardy, Martin]

Dear KW2 CW operators,

yesterday evening I was running into a problem during CW operation with
the K2. I called
CQ using the 1.5 KHz CW filter on 20m and got response from a couple of
US stations.
The signals have been quite weak ( RST 33 ), but I have managed to copy
a call sign and
to give answer.

Because of sudden QRM I switched to the 700 Hz filter but lost the
signal. I have had big
difficulties to "find" the signal of the US station within the 700 Hz
filter. So I switched back
to the 1.5 KHz filter and lived with the QRM.

How can I align the CW filtes, so that I can switch to the narrow CW
filters without
losing the signal?

By the way: It was very impressive again, how powerful CW is under
difficult conditions!

Regards

Martin, DL6KMR
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[Tom Hammond-3]

Hello Martin:

>yesterday evening I was running into a problem during CW operation with
>the K2. I called CQ using the 1.5 KHz CW filter on 20m and got response
>from a couple of US stations.
>
>The signals have been quite weak ( RST 33 ), but I have managed to copy
>a call sign and to give answer.
>
>Because of sudden QRM I switched to the 700 Hz filter but lost the
>signal. I have had big difficulties to "find" the signal of the US station
>within the 700 Hz filter. So I switched back to the 1.5 KHz filter and
>lived with the QRM.
>
>How can I align the CW filtes, so that I can switch to the narrow CW
>filters without losing the signal?
>
>By the way: It was very impressive again, how powerful CW is under
>difficult conditions!

The answer to your problem is that at least one, and possibly more) of your
BFO settings for the CW NOR (or CW REV, whichever you were using) setting
on your K2 have been adjusted to the WRONG SIDE of the filter passband.

Assuming that you are set to 40M, and have selected CW NORmal, ALL of your
BFO settings should be BELOW the center frequency of the filter. And ALL of
your CW REV BFO settings should be ABOVE the center frequency of the filter.

I would suggest you consider downloading Spectrogram v5.1.7 AND the
accompanying K2 filter alignment documents from my web site at

    www.n0ss.net

and using Spectrogram to perform another CAL FIL session on your K2. The
documentation describes how to determine the center frequency of your
filter and how to use Spectrogram to perform the CAL FIL alignment.

73,

Tom Hammond   N0SS

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[Steven Pituch]

Dear Martin,

If your narrow filters are aligned using the Spectrogram software so
that they are all centered on your cw tone (say 600 Hz), then all you
need is to zero beat the signal while in the 1.5 kHz filter, and then it
will stay centered even at 100 Hz.  The instructions for finding and
using Spectrogram are on the Elecraft site.

For a lesson on zero beating see:
http://users.ev1.net/%7Espituch/Steve's%20Page/Radio/CW%20Fun/CW%20Fun.htm

Regards,
Steve, W2MY
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[Don Wilhelm-3]

Steve and all,

I beg to differ - for 2 reasons

First, centering a 1.5 kHz bandpass on 600 Hz will result in the passband
lapping over into the opposite sideband by 150 Hz.  A preferred method is to
set the 700 Hz filter first (centered on 600 Hz) and then observe where the
left edge of the filter bandpass falls on the Spectrogram display (put the
mouse pointer on the filter slope and clicking will leave a red crosshair
marker) - after that, go to the wider filter and change the BFO so that the
left edge of that filter is positioned the same as it is for the 700 Hz
filter (position the filter so the slope falls on the red crosshair marker).

Secondly, the K2 firmware actually works to preserve the pitch of a signal,
and as long as the signal falls anywhere within the passband of the filter,
the pitch will not change - of course there is digital quantizing error to
contend with in the K2, so you may find a pitch change of up to 20 Hz, and
that is not unusual.

73,
Don W3FPR

> -----Original Message-----
>
> If your narrow filters are aligned using the Spectrogram software so
> that they are all centered on your cw tone (say 600 Hz), then all you
> need is to zero beat the signal while in the 1.5 kHz filter, and then it
> will stay centered even at 100 Hz.  The instructions for finding and
> using Spectrogram are on the Elecraft site.
>

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