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

Steve Dimse k4hg at tapr.org
Tue Dec 14 16:53:06 UTC 2004


On 12/14/04 at 10:38 AM Jason Winningham <jdw at eng.uah.edu> sent:

>HAAT is Height Above Average Terrain, and there is a specific formula 
>that goes like this:
>
One thing I do wish to point out is that this is really a legal definition of
HAAT, used by the FCC to deal with antenna height issues. 

PHG is designed to provide an estimate of VHF coverage. My guess is PHG was used
rather than simply transmitting a range distance because P, H, and G are numbers
users can easily guess at, allowing the program to determine the range value. My
opinion is one should not be too hung up on the individual PHG numbers...

Unfortunately PHG has its limitations, and in some cases it would probably be
better to start with a range number a digi covers, and work backwards to get a
PHG value that produces the desired coverage circle...

Steve K4HG




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