[Skimmertalk] [RBN-OPS] What causes audio images with QS1Rs?

Rick Kiessig kiessig at gmail.com
Sat Feb 23 18:07:18 EST 2013

Have you looked at the signals with SDRMAX V, both zoomed-in and in the
wideband display?


Any chance it could be related to interference / front-end overload from
broadcast stations? With my setup, I was seeing wideband noise and spurious
spots from B/C stations before I installed a B/C filter.


With SDRMAX V running, do you see the clipping light come on? The Skimmer
FPGA code doesn't light up the clip light in the same way, so you'll get
more accurate info while running SDRMAX V.


You might also ping Phil N8VB and/or the QS1R reflector. Phil's support has
generally been excellent.


73, Rick ZL2HAM



From: RBN-OPS at yahoogroups.com [mailto:RBN-OPS at yahoogroups.com] On Behalf Of
Pete Smith N4ZR
Sent: Sunday, February 24, 2013 10:30 AM
To: RBN-OPS at yahoogroups.com; Skimmertalk at contesting.com
Subject: [RBN-OPS] What causes audio images with QS1Rs?


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, ones which rely on a
computer sound card for A/D conversion.  That is, the two spots are spaced
equidistant from the receiver's center frequency, one is significantly
stronger than the other, and they arrive at the server typically within the
same second.

We're having no luck isolating what is different about those particular
systems.  So far we've ruled out inadequate power supplies, and the idea of
excessive gain before the receiver doesn't look promising.  Does anyone have
any theories we can explore?  I'll be glad to provide the data in Excel
format for anyone who wants it.

Thanks in advance!

73, Pete N4ZR
Check out the Reverse Beacon Network at 
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite 
ARC V6 or VE7CC DX cluster node.



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