Message-ID: <4CA2536D.9040804@iup.uni-heidelberg.de>
Date: Tue, 28 Sep 2010 22:43:25 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: 137.5kHz ERP calculation based on WSPR reports (G3XBM)
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Hi Roger,

Not sure if the calculations are correct but i wish you nice holidays! 
:-) Where does the tun go? And are you QRV /P on LF? ;-)

73, CU! ;-)

Stefan

Am 28.09.2010 15:46, schrieb Roger Lapthorn:
> 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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Hi Roger,<br>
<br>
Not sure if the calculations are correct but i wish you nice holidays!
:-) Where does the tun go? And are you QRV /P on LF? ;-)<br>
<br>
73, CU! ;-)<br>
<br>
Stefan<br>
<br>
Am 28.09.2010 15:46, schrieb Roger Lapthorn:
<blockquote   cite="mid:AANLkTik3R37E=Q31atFbdURzXaYUcQHQGza7H7wTU+i8@mail.gmail.com"   type="cite">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.<br>
  <br>
Firstly, I've assumed a noise level at Jim's QTH of <b>3uV/m</b>, this
being the figure he gave me last winter for 500kHz.&nbsp; Secondly, I'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 day
the signals have got somewhat worse and are now around -25dB S/N.&nbsp; The
distance between us is <b>69km</b>.&nbsp; So, putting the numbers into
formula:<br>
  <br>
ERP = (Ed)^2/49&nbsp; = [(0.36*10E-6 x 69*10E3)]^2 / 49 =
(0.36*0.36*69*69)/49 uW = <b>12.6uW</b> in Jim's direction.<br>
  <br>
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 <b>25-50uW</b>.&nbsp; 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 and 5W RF driving it.<br>
  <br>
Have I got this right?<br>
  <br>
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.<br>
  <br>
73s<br>
Roger G3XBM<br>
  <br>
  <br>
-- <br>
  <a moz-do-not-send="true" href="http://g3xbm-qrp.blogspot.com/"   target="_blank">http://g3xbm-qrp.blogspot.com/</a><br>
  <a moz-do-not-send="true" href="http://www.g3xbm.co.uk"   target="_blank">http://www.g3xbm.co.uk</a><br>
  <a moz-do-not-send="true" href="http://www.youtube.com/user/g3xbm"   target="_blank">http://www.youtube.com/user/g3xbm</a><br>
G3XBM&nbsp;&nbsp; GQRP 1678&nbsp;&nbsp;&nbsp; ISWL G11088<br>
</blockquote>
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