[Skimmertalk] Skimmer Signal Detection Levels

Rick Walker rnwalker at bellsouth.net
Wed Oct 29 12:55:34 EDT 2008


Pete,

Thanks for the quick response.  I agree that QSB and QRN can certainly get
in the way of a proper decode and hence a skimmer spot report.  I am
probably remiss for not putting into my previous post the fact that I asked
the skimmer application to show me the "raw data" it had decoded on these
signals.  There was generally nothing to display...  It seems to me that
there is some sort of squelch on the decoder input that prevents it from
decoding until a minimum signal threshold is available.  I don't inherently
have a problem with that sort of algorithm, but I wish the threshold level
were operator defined so I could adjust it to local conditions...

I'm also still convinced that we need to replace the RX location in the spot
"Remarks" field with something useful like detected signal level.  I believe
this information might be available via the SDR-IQ output data stream since
the SpectraVue application that comes with the SDR-IQ receivers provides
this sort of information on its graphical user interface.  At the very
least, if Alex's algorithm calculates and/or determines its own estimate of
the SNR then this information would still be useful if made available.

If the long-term objective is to keep skimmer spots off the main DX cluster
backbone (BTW, I don't have an opinion on this one way or another) then it
seems to me that we could take some active steps toward mining the wealth of
information that must surely be available from our local skimmer
applications.  At the very least we could determine what interesting
information is available from skimmer and give a local user the ability to
customize the "Remarks" field is a manner that facilitates his/her analysis
activities...  I weep for the lost opportunities every time I see my own
gridsquare come across in the "Remarks" field of one of my skimmer spots...
:-)

73,

Rick
K4TD




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