[Skimmertalk] 160M Skimmer Observations

Fri Dec 4 06:28:50 PST 2009

Were you watching just for the spots or looking at the waterfall and raw
decoded text?  

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net

> -----Original Message-----
> From: Rick Walker [mailto:rnwalker at bellsouth.net]
> Sent: Friday, December 04, 2009 13:05
> To: skimmertalk at contesting.com
> Subject: [Skimmertalk] 160M Skimmer Observations
> Last night I hooked my 160M SDR-IQ/CW Skimmer combo to my main 160M
> receive
> array (the combo is normally connected to a less capable but
> omni-directional RX antenna).  I was listening to some EU stations on 160
> and noticed that I could quite easily copy them on my K3 but that CW
> Skimmer
> wasn't spotting them even though both the K3 and SDR-IQ receivers were
> using
> the same RX antenna system.  I have long thought that CW Skimmer didn't
> "dig
> signals out of the noise" as well as it could, but I thought that maybe in
> this case the issue was the performance of the SDR-IQ versus the K3.  On a
> whim, I took down the CW Skimmer application and started SpectraVue to
> determine if the SDR-IQ was the bottleneck.  Interestingly, the signal in
> question was clearly visible on the SpectraVue pan display and SpectraVue
> demodulated the CW signal quite easily.  This little experiment caused me
> to
> do more thinking about the problem than I had previously done.  Some
> questions arise as a result:
> 1.  Is there some sort of "artifical squelch" within CW Skimmer?
> 2,  How does Alex computes the noise floor used in the S/N calculation
> produced by CW Skimmer?
> 3.  Anyone ever correlated the S/N value produced by their CW Skimmers
> with
> any specific signal level parameter found by manually observing the same
> signal with their station receivers?
> I apologize if I bring up something that has been dealt with in the past.
> I
> searched on this subject but didn't find much.
> 73,
> Rick
> K4TD
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