RF range - plane earth model

[Ian]

G'Day all,

Can anyone give me the quick summary as to why the plane eath RF
propogation model doesn't include a frequency term?

I have seen a reference that the plane earth model is pretty much only
useful in the UHF band and hence maybe the freq term becomes
insignificant, that is the additional loss introduced by frequency
does not vary much over the UHF range. Is that the reasoning?

http://www.radioinnovation.com/Howto/how_far2.htm gives some details
but it bothers me that freq doesn't come into it.

My application is *not* inbuilding so I am not using one of the more
elaborate scattering models. However, my antenna heights are
potentially quite low, so I suspect a simple plane-earth model will be
somewhat optimistic, anyway.

Thanks,
Ian

 

[Charles Schuler]

G'Day all,

Can anyone give me the quick summary as to why the plane eath RF
propogation model doesn't include a frequency term?

I have seen a reference that the plane earth model is pretty much only
useful in the UHF band and hence maybe the freq term becomes
insignificant, that is the additional loss introduced by frequency
does not vary much over the UHF range. Is that the reasoning?

At longer wavelengths (frequencies around 2 MHz or lower) the wavefront
loses energy due to currents induced in the Earth. This causes the wave to
tilt forward and follow the Earth's curvature producing propagation
distances well beyond the line of sight. Consider WWVB propagation at 60
kHz.

 

[Joe McElvenney]

Hi,

Can anyone give me the quick summary as to why the plane eath RF
propogation model doesn't include a frequency term?

I have seen a reference that the plane earth model is pretty much only
useful in the UHF band and hence maybe the freq term becomes
insignificant, that is the additional loss introduced by frequency
does not vary much over the UHF range. Is that the reasoning?

The complete expression has terms in lambda but the d^4 approximation
is used when 'd' is large with respect to the antenna heights. Have a
look at --


http://www.wireless.per.nl:202/multimed/cdrom97/pel.htm


Cheers - Joe