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K3 and CW-Skimmer

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Martin-2

K3 and CW-Skimmer

Elecrafters,
i know this is not the right place - and off topic- , but i hope for a
quick solution to the problem without the need to subscribe to yet
another forum.

Problem:
I set up CW-Skimmer / LPPan / K3 .
When i click on a signal i see on the waterfall, the K3 jumps to that
frequency. In some cases i then hear and see the signal exactly where i
expected it, in other cases the signal shows up in a different place on
the waterfall. I tried to compensate for that offset per the manual ,
but i just don't understand the mechanism behind it. The manual says
24000 ( might be 2400 as well - i don't have cw-skimmer on _this_ pc )
is a good starting point, but that seems to be _far_ off.

Any one?

--

73,
Martin DM4iM
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Arie Kleingeld PA3A-2

Re: K3 and CW-Skimmer

Martin,

I use a softrock instead of a LP-PAN but it works on about the same
principles I think.
It is used on a K3 with PDSR-IF as software. CW-skimmer is just used
sometimes, just for the fun of it.

In PDSR-IF all kinds of data are read from the K3 to keep everything in
place on screen after you have set the IF-offset.
No matter what bandwidth or mode you use, PDSR-IF follows the K3. Nice
software.

The CWSkimmer works different, I think it only uses the offset you set
in the CWskimmer options.

For CW operation BWs, the roofers that are used in my K3 are 2.1k , 400
and 200.
If I set the CWskimmer on the right freq with the 400Hz roofingfilter, I
see the signals shift in the display if I change BW enough so that
another roofing filter kicks in.

When using different roofing filters in the K3, the IF-offset changes a
bit in the K3, if you switch to another roofing filter, if I understand
it correctly.. It has been explained in this reflector that this happens
for a reason. It has to do with the way the roofing filter is placed
over the signal you are listening to. There are experts that can explain
what happens exactly. (So some more info is needed please.)

I was not aware of this problem untill I used CW skimmer and the N1MM
logger bandmap and saw that I had to keep the 400 roofer in place
otherwise the spots would be placed on the wrong freq in the bandmap. So
that's what happened here.

I wonder if others have seen this behaviour and what they did about it.

73
Arie PA3A

Op 23-2-2011 11:01, DM4iM schreef:

> Elecrafters,
> i know this is not the right place - and off topic- , but i hope for a
> quick solution to the problem without the need to subscribe to yet
> another forum.
>
> Problem:
> I set up CW-Skimmer / LPPan / K3 .
> When i click on a signal i see on the waterfall, the K3 jumps to that
> frequency. In some cases i then hear and see the signal exactly where i
> expected it, in other cases the signal shows up in a different place on
> the waterfall. I tried to compensate for that offset per the manual ,
> but i just don't understand the mechanism behind it. The manual says
> 24000 ( might be 2400 as well - i don't have cw-skimmer on _this_ pc )
> is a good starting point, but that seems to be _far_ off.
>
> Any one?
>
>

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Bill W4ZV

Re: K3 and CW-Skimmer

Arie Kleingeld PA3A-2 wrote

When using different roofing filters in the K3, the IF-offset changes a
bit in the K3, if you switch to another roofing filter, if I understand
it correctly.. It has been explained in this reflector that this happens
for a reason. It has to do with the way the roofing filter is placed
over the signal you are listening to. There are experts that can explain
what happens exactly. (So some more info is needed please.)

I was not aware of this problem untill I used CW skimmer and the N1MM
logger bandmap and saw that I had to keep the 400 roofer in place
otherwise the spots would be placed on the wrong freq in the bandmap. So
that's what happened here.

I wonder if others have seen this behaviour and what they did about it.

Your understanding is correct. Each time the K3 changes roofing filters, a different offset is required for CW Skimmer to zero beat unless (the filters have identical offsets). This is one good reason to select all 8-pole filters since they have identical offsets of zero. Yes, before someone says it, I know the 8-pole offsets are not actually zero but it doesn't matter since the offsets are a small percentage of total bandwidth (even the "250" which is actually 370.

In contests I use both a 500 Hz Inrad 8-pole and a 200 Hz Elecraft 5-pole. For the CQ 160 which is EXTREMELY crowded, I used the 200 Hz 99% of the time (both for running and for S&P with Blind Skimmer) so I set Skimmer's offset for the 200 Hz filter offset. In the ARRL DX, which is not so crowded, I used the 500 Hz when running (when I don't need a waterfall) but then adjusted WIDTH so the 200 Hz was activated when using Blind Skimmer to S&P on the waterfall decoder dots. Since Skimmer's decoder dots are so accurate in placing the K3 passband on signals of interest, the simplest thing to do is to always use your narrowest filter setting for Skimmer. You could quickly change this by making Filter Preset I for "normal" use and Preset II for "Skimmer" use.

Another thing I do is record the two different offsets for Skimmer (for the 500 Hz and 200 Hz filters) and paste it above the appropriate place on my monitor. Then I can quickly adjust Skimmer's Setting Menu if I ever need to change the filter used with Skimmer.

73, Bill

Arie Kleingeld PA3A-2

Re: K3 and CW-Skimmer

Bill,

Thanks for the confirmation.

I'm not an expert in how this software works to get the the signals
displayed on the right freq.
It seems to me that CWskimmer uses the displayed receive frequency as
data to work with. It would probably work better if it would use (by
computing using data from the K3) the VFO (1st oscillator) freq. This is
probably done by the PSDR-IF software authors. (just guessing here)

(As a registered user of CWskimmer I would applaude for a fix on this
issue :-) )

73 Arie PA3A

Op 23-2-2011 14:43, Bill W4ZV schreef:

>
> Arie Kleingeld PA3A-2 wrote:
>> When using different roofing filters in the K3, the IF-offset changes a
>> bit in the K3, if you switch to another roofing filter, if I understand
>> it correctly.. It has been explained in this reflector that this happens
>> for a reason. It has to do with the way the roofing filter is placed
>> over the signal you are listening to. There are experts that can explain
>> what happens exactly. (So some more info is needed please.)
>>
>> I was not aware of this problem untill I used CW skimmer and the N1MM
>> logger bandmap and saw that I had to keep the 400 roofer in place
>> otherwise the spots would be placed on the wrong freq in the bandmap. So
>> that's what happened here.
>>
>> I wonder if others have seen this behaviour and what they did about it.
>>
> Your understanding is correct. Each time the K3 changes roofing filters, a
> different offset is required for CW Skimmer to zero beat unless (the filters
> have identical offsets). This is one good reason to select all 8-pole
> filters since they have identical offsets of zero. Yes, before someone says
> it, I know the 8-pole offsets are not actually zero but it doesn't matter
> since the offsets are a small percentage of total bandwidth (even the "250"
> which is actually 370.
>
> In contests I use both a 500 Hz Inrad 8-pole and a 200 Hz Elecraft 5-pole.
> For the CQ 160 which is EXTREMELY crowded, I used the 200 Hz 99% of the time
> (both for running and for S&P with Blind Skimmer) so I set Skimmer's offset
> for the 200 Hz filter offset. In the ARRL DX, which is not so crowded, I
> used the 500 Hz when running (when I don't need a waterfall) but then
> adjusted WIDTH so the 200 Hz was activated when using Blind Skimmer to S&P
> on the waterfall decoder dots. Since Skimmer's decoder dots are so accurate
> in placing the K3 passband on signals of interest, the simplest thing to do
> is to always use your narrowest filter setting for Skimmer. You could
> quickly change this by making Filter Preset I for "normal" use and Preset II
> for "Skimmer" use.
>
> Another thing I do is record the two different offsets for Skimmer (for the
> 500 Hz and 200 Hz filters) and paste it above the appropriate place on my
> monitor. Then I can quickly adjust Skimmer's Setting Menu if I ever need to
> change the filter used with Skimmer.
>
> 73, Bill
>

Arie Kleingeld PA3A-2

Re: K3 and CW-Skimmer

In reply to this post by Bill W4ZV

Bill,

BTW, it happens also when switching from 400 to 2100 (both zero offset).

From the earlier explanation I remember that the side of the filter BW
is placed on the side of a signal. (I donot know how to say it a better
way). The filter is not placed symmatrically.
So when changing the filter, and also when I change the shift, the
CWskimmer display moves..

73
Arie PA3A

Op 23-2-2011 14:43, Bill W4ZV schreef:

Bill W4ZV

Re: K3 and CW-Skimmer

In reply to this post by Arie Kleingeld PA3A-2

Arie Kleingeld PA3A-2 wrote

Bill,

Thanks for the confirmation.

I'm not an expert in how this software works to get the the signals
displayed on the right freq.
It seems to me that CWskimmer uses the displayed receive frequency as
data to work with. It would probably work better if it would use (by
computing using data from the K3) the VFO (1st oscillator) freq. This is
probably done by the PSDR-IF software authors. (just guessing here)

I believe PSDR reads the offsets for each different filter and automatically corrects, although I have not used PSDR in nearly 3 years so I could be wrong. Skimmer only uses a single offset entered in the Setting Menu. The information about different filter offsets is available in the K3's output but Alex does not use it. I also wish he would lift the 24 kHz limitation for the Software on IF mode used with the K3 but so far he hasn't.

I use Skimmer directly with the K3/LP-PAN (no PSDR) since I much prefer its waterfall. PSDR is nice but overly complex for what I need.

73, Bill

Bill W4ZV

Re: K3 and CW-Skimmer

In reply to this post by Arie Kleingeld PA3A-2

On Wed, Feb 23, 2011 at 11:19 AM, Arie Kleingeld PA3A <[hidden email]> wrote:

> BTW, it happens also when switching from 400 to 2100 (both zero offset).
>
> From the earlier explanation I remember that the side of the filter BW is
> placed on the side of a signal. (I donot know how to say it a better way).
> The filter is not placed symmatrically.
> So when changing the filter, and also when I change the shift, the CWskimmer
> display moves..

You're probably correct about the 2.1k filter not being centered in CW
mode, which causes the offset. I never use such a wide filter with
Skimmer so I never noticed what you described.

73, Bill
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