DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=googlemail.com; s=gamma;
        h=mime-version:date:message-id:subject:from:to:cc:content-type;
        b=pRDpJfOgAlTjfMmmQIMRYcu0BAft7Zco1wWELSeJ0H4zQ/o7pFbBAo0RgdIDNCxKF+
         g17AIgemUz89lguD0VAPNSvF0/sF3X9uwY3u77zE4bBflpMadbfHF6/Sk/zIhgFytuXh
         iNHxyePfd7uL4/0GcxwILItRxwrQp5kIyWRDA=
MIME-Version: 1.0
Date: Sun, 7 Feb 2010 18:20:42 +0000
Message-ID: <fc7eccec1002071020g1f1fe66dq4bd363e8d4142c39@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
Cc: jfell@tesco.net
DomainKey-Status: good (testing) 
Subject: LF: WSPR S/N Tests
Content-Type: multipart/alternative; boundary=000325559bba13eb1e047f06be5e
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


--000325559bba13eb1e047f06be5e
Content-Type: text/plain; charset=ISO-8859-1

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.

Andy
www.g4jnt.com

--000325559bba13eb1e047f06be5e
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

<div>To try to get to grips with the falsely high values of=A0 S/N reporte=
d 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.</di=
v>
<div>=A0</div>
<div>The results were dramatic.=A0 With=A0receive bandwidths less than 300=
Hz, the reported S/N increased considerably.=A0=A0 It was only possible to=
 use bandwidths in steps of 500Hz so 100,150,200 etc with the SDR-IQ=A0but=
 these were more than enough to show the effect.</div>

<div>=A0</div>
<div>Full details can be found in <a href=3D"http://www.g4jnt.com/WSPR_SNR=
_Test.pdf">www.g4jnt.com/WSPR_SNR_Test.pdf</a>=A0 but the results can be=
 summarised as :</div>
<div>=A0</div>
<div>-------------=A0=A0 Don&#39;t use a bandwidth below 300Hz unless you=
 want artificially high SNR reports=A0=A0 =A0-----------------------</div>
<div>=A0</div>
<div>300Hz or anything higher that allows the decoding software to see the=
 full noise band is OK.</div>
<div><br clear=3D"all">Andy<br><a href=3D"http://www.g4jnt.com/" target=3D=
"_blank">www.g4jnt.com</a><br></div>

--000325559bba13eb1e047f06be5e--