Message-ID: <51472B6F.2090509@iup.uni-heidelberg.de>
Date: Mon, 18 Mar 2013 15:57:51 +0100
From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: WSPR -2 SNR
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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