Hi Roelof,
A spontaneous speculation:
-Higher phase changes on HF and 160m (?)
-Most WSPR RX stns on HF and 160m use HF TRXs which could have a higher
drift than many SDRs on MF and LF
-Same applies for the generation of WSPR signals (drift issue)
-More stations with high SNR in the same 200 Hz BW on HF and 160m
and so on ;-)
73, Stefan/DK7FC
Am 18.03.2013 15:07, schrieb Roelof Bakker:
Hello all,
On the WSPR website,
http://physics.princeton.edu/pulsar/K1JT/wspr.html
I find this statement:
The program can decode signals with S/N as low as -28 dB in a 2500
Hz bandwidth. <<<
I have been looking at decodes on WSPR Spots
http://wsprnet.org/olddb
and it appears that on bands from 160 m and up a SNR smaller than -25
dB is a bit rare.
On 630 m these low level decodes are found more often, though decodes
with an SNR of -30 are rare.
In the nigh of Saturday to Sunday, I had 14 decodes from WG2XJM.
Two of these showed a SNR of -33 dB.
I have never seen such a low SNR before and a search through the WSPR
Spots database showed a decode from a French listener of WG2XJM with
an SNR of -31, which is the lowest SNR I could find.
As far as I know the bandwidth of the WSPR decoder is set to 200 Hz,
so as long as the receiver bandwidth is larger than 200 Hz, decoding
should not be effected. My receiver bandwidth is 540 Hz.
So, has anyone an idea what is the cause of these low level WSPR decodes.
Best regards,
Roelof Bakker, pa0rdrt
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