[Skimmertalk] Skimmer Advice (K3 IF issues)

Pete Smith N4ZR n4zr at contesting.com
Tue Nov 10 09:12:15 EST 2015

Hi Pat - so long as you are using CW Skimmer in the Softrock-IF mode, 
there is no way that you can cover more than +/- 12 KHz from the center 
frequency.  This is a Skimmer software-imposed limitation, one for which 
I do not understand the rationale, because NaP3 on the output of LP-Pan 
definitely is not restricted. To get the coverage you want, you really 
need to listen with the Afedri to the RX out from your K3, probably with 
a splitter after the RC protector.  The Afedri can be set up to work 
this way, but only on one 192-KHz band at a time. You can use SkimScan 
to make it alternate between any two bands, or more.

I think your issue with changing frequencies when you change filter 
bandwidths may be due to incorrect LP-Pan or
LP-Bridge settings, because I do not encounter this.

One problem with using RX Out - I believe that the K3's bandpass 
filtering may preclude some 2-band combinations from working (40 and 20 
for example).  All in all, I think that a better solution may be to use 
a separate antenna, or to connect to a "retail" DX Cluster - either ARC 
V6 or VE7CC - and set up your filters so that you only get spots sent by 
RBN nodes that have approximately the same propagation that you do.  Of 
course, if you want to run as unassisted you can't do that.

73, Pete N4ZR
Download the new N1MM Logger+ at
<http://N1MM.hamdocs.com>. Check
out the Reverse Beacon Network at
<http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 11/9/2015 6:26 PM, Pat Rundall wrote:
> Skimmer Gurus...
> I'm looking for a bit of advice on how to improve my setup for CW contests.
> Namely, I'd like to avoid the 24khz limit of the k3/LP-Pan setup and issues
> with the output shifting frequencies when I change filter settings on the
> k3.
> The Goal:
> Aggregate useful skimmer spots -> N1MM+ for the current and adjacent bands.
> I'd prefer to have the skimmer running on the active antenna (ie a beam
> rather than a short vertical or loop)
> The Current Setup
>     - N1MM+ on a laptop
>     - K3/100 as the main rig w/RX2
>     - LP-Pan2 from IF-Output of K3
>     - USB sound card capable of 192khz
>     - Currently, I'm routing the RX output of the k3, through a
>     DX-Engineering RX-Guard and then into the RX input as a means of protecting
>     the front end in a SO2R environment (also using BPFs, etc.). (100w)
>     - Aggregating spots from a local packet node with wintelnetx
> Other HW available
>     - Afedri SDR
>     - Pixel RX loop
> The problem
> I noticed in Sweepstakes CW that the Skimmer is only decoding +/-12khz
> rather than the whole 192kHz at once. Also noticed that when I change
> filter settings on the k3, the frequency jumps on Skimmer. I've read where
> both of these issues are known and there really isn't a working solution
> apart from simply using other hardware. Unless I've missed it, I don't see
> a solution to these issues offered by the vendors (Elecraft/LP-Pan/VE3NEA)
> Options
>     1. Setup the Afedri SDR to be a standalone receiver by putting a
>     splitter after the RX-Guard on the RX-out/in loop. I may see a bit of
>     signal loss on that. I'd probably setup the Afedri on a separate PC running
>     an SDR app (HDSDR?) with Skimmer. Then when I change bands, manually change
>     that on the app. Not horribly inconvenient.
>     2. Setup the SDR on the RX loop with another RX Guard. (Even if there is
>     a fix to the K3 IF issues, I may setup another SDR on the loop to monitor
>     the adjacent band)
> Other thoughts?
> Thanks
> Pat N0HR
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