[Elecraft] K3 and CW-Skimmer

[Arie Kleingeld PA3A]

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
>