Topband: Ground conductivity, permittivity measurement

[Richard Fry]

Cristi YO3FFF wrote:

> From Terman (as Richard Fry mentioned): 
> http://i62.photobucket.com/albums/h85/rfry-100/TermanFig55.jpg

> First hop distance on E layer reflection for given angles is:
> 20 degrees = 300miles, 30 degrees = 200miles
______________

But note that Terman shows much longer 1st-hop skywave paths at elevation 
angles below three degrees -- where a NEC far-field pattern of a vertical 
monopole over real earth shows very low relative field from a vertical 
monopole.

A NEC far-field pattern of a vertical monopole over real earth also shows 
zero field in the horizontal plane, but clearly that is incorrect.  If it 
WAS correct, then AM broadcast stations would have zero daytime coverage by 
their surface (ground) wave.  Yet a 50 kW station on a low frequency can 
provide useful groundwave service beyond 200 miles from their antenna site, 
in many cases.

The surface wave MUST be considered when evaluating skywave performance of a 
monopole, because that surface wave contains significant radiation at low 
elevation angles capable of producing skywave coverage.

This was shown clearly in the NEC4.2 plot posted by Paul Christensen earlier 
in this thread, at http://72.52.250.47/images/160m.jpg , and also in my link 
http://i62.photobucket.com/albums/h85/rfry-100/Measured_vs_NEC2D_Fields2.jpg

R. Fry