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From: "James Cowburn" <james.cowburn@virgin.net>
To: <rsgb_lf_group@blacksheep.org>
References: <9afca2640909181501s4ea78076wf335f218ab07a106@mail.gmail.com> <PAEFLMFGBDKKCONLMLBIMENKDEAA.ganymede444@btopenworld.com> <9afca2640909190053uc3188c8ja0529072f1b42955@mail.gmail.com> <65021672466E4DA891D8CC98B984A4AA@JimPC>
Date: Sat, 19 Sep 2009 11:47:44 +0100
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Subject: LF: RE: RE: 500kHz QRPp WSPR overnight
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As I found out, relatively small improvements/changes to the system result
in substantial improvements in performance.
The mini VNA has been a real help in getting stuff aligned.
Jim - using this formula could you estimate what my ERP is?
With best regards
Jim
Dr. James Cowburn
-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of James Moritz
Sent: 19 September 2009 10:28
To: rsgb_lf_group@blacksheep.org
Subject: LF: RE: 500kHz QRPp WSPR overnight
Dear Roger, LF Group,
It is interesting to make an estimate of what G3XBM's ERP might be...
The noise level at M0BMU during relatively quiet daytime conditions I
estimate to be of the order of 3uV/m in the 2.5kHz WSPR reference bandwidth.
The reported SNR gets up to about -25dB, making the signal level from G3XBM
about 0.18uV/m.
ERP = (Ed)^2 / 49; with E = 0.18 x 10e-6, d = 69000m , ERP is about 3uW with
only "geometric spreading" propagation losses. But there is some additional
reduction in field strength due to ground wave propagation losses, perhaps
3dB with "good" ground, so the ERP would then become about 6uW. Diffraction
losses due to the curvature of the earth are negligible at this distance.
Obviously, this could be +/- several dB due to various uncertainties, but
should be of the right order of magnitude. Plenty of potential for
improvement then!
Cheers, Jim Moritz
73 de M0BMU