[Skimmertalk] What causes audio images with QS1Rs?

Bob Wilson, N6TV n6tv at arrl.net
Sat Feb 23 23:22:22 EST 2013

On Sat, Feb 23, 2013 at 1:30 PM, Pete Smith N4ZR <n4zr at contesting.com>wrote:

> During the ARRL CW contest, we had two Skimmers using the QS1R/Skimmer
> Server combination that each produced many false spots, with the
> "signature" commonly associated with Skimmers using simple SDRs,

I hope my QS1R wasn't one of them.  Noticing the same thing happening
before the contest, 10m only, with 192 kHz bandwidth, I went ahead and
edited my SkimSrv.ini file (used for "Contest rotation") to force it to
ignore all signals 130 kHz or more above the band edge.





Here are some numbers that could reveal a new problem in CW Skimmer and/or
SkimSrv being introduced in the last year, that lead to more false image
signals being reported, though the evidence may not be 100% conclusive:

Contest              RBN       RBN Spots    % of
                  10m Spots  >= 28100 kHz   Spots
---------------  ----------  ------------   -----
2012 ARRL DX CW      93,317        502      0.54%
2012 WPX CW         132,751        332      0.25%
2012 CQ WW CW       244,242      6,249      2.56%
2013 ARRL DX CW     178,404      2,644      1.48%

Bob, N6TV

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