Topband: Modeling the proverbial "vertical on a beach"

[Richard Fry]

The link in the opening post of this thread shows an interesting, animated 
analysis of the elevation gains of a monopole, based on a NEC far-field 
analysis not including the surface wave.

I then posted this comment, "Reality is that radiation leaving the monopole 
at elevation angles of at least 5 degrees decays at a 1/r rate. Therefore 
that radiation is a space wave which propagates in a ~ straight line to 
reach the ionosphere, where (with suitable conditions) it can return to the 
earth as a skywave."

Others have been skeptical that this low-angle radiation was a space wave 
that could reach the ionosphere.

Recently I investigated this more closely, leading to the NEC4.2 study 
linked below.  It shows that the 3.8 MHz radiation existing on a departure 
angle of 5 degrees at a distance of 3/10 of a mile from a monopole continues 
on toward the ionosphere along that path, while its value decays at a 1/r 
rate -- indicating that it is a space wave.

http://s20.postimg.org/6yau4m225/Monopole_Radiation_5_deg_Departure.jpg