LF: RE: 500kHz QRPp WSPR overnight

["James Moritz" <james.moritz@btopenworld.com>]

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