Piotr Mlynarski wrote:

> one can mention the semiempirical Austin equation  describing
> E field  dependence upon distance  based on the idea of a
> spatial waveguide: earth-ionosphere.

That's a step forward.

Up to now we've tried

 B = sqrt( 9.5e-21 * ERP/r) * exp( -r/a)

where a = 2.9e6 for daytime path, or 4.3e6 for nighttime
path.   This assumes radiated power is spread uniformly
over the circumference of a cylinder expanding across
a flat earth, and the signal is trapped between earth
and 70km ionosphere.

I can see that an extra factor involving alfa/sin(alfa)
(alfa = r/earth_radius) will be necessary to allow for spherical
earth.

Piotr, I've just found your post of 29th Jan, I'll go read that
now...  thanks for the tip.
--
Paul Nicholson
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