Re: LF: RE: 500kHz QRPp WSPR overnight

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Dear Jim (et al),

Thanks for this interesting analysis. It does indeed suggest plenty of scope for improvement in the coming months. 

As I've said several times in the last week, I'm gobsmacked that anyone, apart from G6ALB 3kms away, is able to hear me with the set-up I have. The 500kHz WSPR beacon will run one more time overnight tonight  then it will be off for 2-3 weeks.  

My wife is wanting her dressing table back as the tiny ATU is sitting
on it and tuning is very sharp; every time she puts anything down I have
to check the antenna current is peaked :-))

You know I'm like a kid: I get so excited looking at the spots and thinking about gradually making improvements and seeing my coverage extend on 500kHz. 

My wife just humours me!

73s
Roger G3XBM

2009/9/19 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

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