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[aprssig] bad PHG, or lots of big towers?

Robert Bruninga bruninga at usna.edu
Fri Dec 17 13:05:00 UTC 2004

>>> kb8uih at sbcglobal.net 12/15/04 5:56:15 PM >>>
>I would still ask exactly what is average terrain?  

The answer has been posted several times.  The
FCC definition is all terrain going out 10 miles.  The
real practical answer is "that area of ground over
which you expect the signal to reach".

>Is it the spot of ground the tower sits on or is it
>something else?

Has nothing to do with that at all.

>If a small mountain say 5k high sits in the middle of
>a plain somewhere, from where is the average terrain

Depends on the diameter of the Mountain if using the
FCC method.  In practical terms I'd look at the terrain
going out 100 miles from that one...  Because at that
altitude, the signal can go that far.

Unless of course the altitude of the "plain" around that
5000 foot mountain is at 4000 feet, then of course the
range would be much less, and so I'd look at the terrain
going out in the 20 to 50 mile range for my average...

>The base of the tower or the flat land at the base of
>the mountain?

It is an exceedling simple concept.  How high is the
antenna above the "ground" area that the transmitter is
trying to serve...


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