On 17 Sep 2009 at 9:23, Roger Lapthorn wrote:
> Just had these 2 reports. I am very surprised WSPR can detect these low
> S/N levels...
>
> 2009-09-17 08:12 G3XBM 0.503838 *-33* 1 JO02dg 0.001 G7NKS
> IO92ub 46 240 2009-09-17 07:56 G3XBM 0.503839 * -32* 0 JO02dg
> 0.001 G7NKS IO92ub 46 240
> 73s
> Roger
Still nothing at all here Roger, there were a couple of very weak
broken lines on the waterfall but no copy.
I tend to take the dB figures in WSRP with a pinch of salt. Jim, James
and Gus are quite strong signals and not only audible by ear all the
time but reading well on the s meter - James 579, Gus peaking over s9
at times but with deep QSB, and Jim - if it wasn't a row of LEDs it
would be bending the meter. G7NKS shows between -3dB and -17dB on WSPR
(with the input adjusted for a correct 0dB on noise), implying he is
below the noise... I think all that can be deduced is the relative
strengths against an unknown reference. With the signals heard here
WSPR7 gives reliable decodes down to around -20dBm and a few gibberish
decodes at the -30dBm level. I have not copied anything lower, and when
I do get decodes the signal is easily copyable by ear and a very
obvious line on the spectrogram.
One point is that with the K2 you cannot set a narrow filter at 1.5kHz
(a limitation of the tuning range of its IF BFO). I am sure if you used
such a narrow receive filter the results would be spectacularly better,
but I am stuck with the SSB filter.
73 Dave G3YMC
http://www.davesergeant.com
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