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Date: Tue, 28 Sep 2010 14:46:17 +0100
Message-ID: <AANLkTik3R37E=Q31atFbdURzXaYUcQHQGza7H7wTU+i8@mail.gmail.com>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: rsgb_lf_group@blacksheep.org
DomainKey-Status: good (testing) 
Subject: LF: 137.5kHz ERP calculation based on WSPR reports (G3XBM)
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This morning M0BMU started listening on 137.5kHz WSPR again and I now have a
bank of reports from Jim 69km away from me. Using this data I've attempted
to make some revised ERP calculations based on some working assumptions.

Firstly, I've assumed a noise level at Jim's QTH of *3uV/m*, this being the
figure he gave me last winter for 500kHz.  Secondly, I've taken the best
WSPR S/N reports received from Jim (*-19dB S/N*). So my signal level with
Jim is around *0.36uV/m*. During the day the signals have got somewhat worse
and are now around -25dB S/N.  The distance between us is *69km*.  So,
putting the numbers into formula:

ERP = (Ed)^2/49  = [(0.36*10E-6 x 69*10E3)]^2 / 49 = (0.36*0.36*69*69)/49 uW
= *12.6uW* in Jim's direction.

Now, I'm using a loop antenna, and I believe Jim is not in the main line of
fire, so another 3-6dB down on the power in the main direction. This would
suggest that in the better directions off the end of the loop the ERP could
be as high as *25-50uW*.  Ground wave propagation losses may also mean the
ERP is another 6dB higher (?) suggesting a possible ERP as high as *
100-200uW* although this seems optimistic with my modest loop and 5W RF
driving it.

Have I got this right?

Incidentally, thank you for all the responses on "loops on the ground". I
can understand what people are saying so will try to elevate the lower part
of the loop when I get back from my holiday in a few weeks' time.
Incidentally this means no LF work from Oct 3-19th is possible.

73s
Roger G3XBM


-- 
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088

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This morning M0BMU started listening on 137.5kHz WSPR again and I now have=
 a bank of reports from Jim 69km away from me. Using this data I&#39;ve at=
tempted to make some revised ERP calculations based on some working assump=
tions.<br>
<br>Firstly, I&#39;ve assumed a noise level at Jim&#39;s QTH of <b>3uV/m</=
b>, this being the figure he gave me last winter for 500kHz.=A0 Secondly,=
 I&#39;ve taken the best WSPR S/N reports received from Jim (<b>-19dB S/N<=
/b>). So my signal level with Jim is around <b>0.36uV/m</b>. During the da=
y the signals have got somewhat worse and are now around -25dB S/N.=A0 The=
 distance between us is <b>69km</b>.=A0 So, putting the numbers into formu=
la:<br>
<br>ERP =3D (Ed)^2/49=A0 =3D [(0.36*10E-6 x 69*10E3)]^2 / 49 =3D (0.36*0.3=
6*69*69)/49 uW =3D <b>12.6uW</b> in Jim&#39;s direction.<br><br>Now, I&#39=
;m using a loop antenna, and I believe Jim is not in the main line of fire=
, so another 3-6dB down on the power in the main direction. This would sug=
gest that in the better directions off the end of the loop the ERP could=
 be as high as <b>25-50uW</b>.=A0 Ground wave propagation losses may also=
 mean the ERP is another 6dB higher (?) suggesting a possible ERP as high=
 as <b>100-200uW</b> although this seems optimistic with my modest loop an=
d 5W RF driving it.<br>
<br>Have I got this right?<br><br>Incidentally, thank you for all the resp=
onses on &quot;loops on the ground&quot;. I can understand what people are=
 saying so will try to elevate the lower part of the loop when I get back=
 from my holiday in a few weeks&#39; time. Incidentally this means no LF=
 work from Oct 3-19th is possible.<br>
<br>73s<br>Roger G3XBM<br><br><br>-- <br><a href=3D"http://g3xbm-qrp.blogs=
pot.com/" target=3D"_blank">http://g3xbm-qrp.blogspot.com/</a><br><a href=
=3D"http://www.g3xbm.co.uk" target=3D"_blank">http://www.g3xbm.co.uk</a><b=
r><a href=3D"http://www.youtube.com/user/g3xbm" target=3D"_blank">http://w=
ww.youtube.com/user/g3xbm</a><br>
G3XBM=A0=A0 GQRP 1678=A0=A0=A0 ISWL G11088<br>

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