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| Subject: | LF: WSPR S/N Tests |
| From: | Andy Talbot <[email protected]> |
| Date: | Sun, 7 Feb 2010 18:20:42 +0000 |
| Cc: | [email protected] |
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To try to get to grips with the falsely high values of S/N reported by some stations recently, I made a set of controlled measurements over a direct link using a range of Rx bandwidths and input signal levels.
The results were dramatic. With receive bandwidths less than 300Hz, the reported S/N increased considerably. It was only possible to use bandwidths in steps of 500Hz so 100,150,200 etc with the SDR-IQ but these were more than enough to show the effect.
Full details can be found in www.g4jnt.com/WSPR_SNR_Test.pdf but the results can be summarised as :
------------- Don't use a bandwidth below 300Hz unless you want artificially high SNR reports -----------------------
300Hz or anything higher that allows the decoding software to see the full noise band is OK.
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