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[aprssig] PHG calculators

Pentti Gronlund pentti.gronlund at tut.fi
Mon Jan 12 18:50:18 UTC 2009


Robert Bruninga writes:

> > There is another weakness in the PHG 
> > notation where the front-to-back
> > ratio is left out to the reader's 
> > imagination.
> 
> Actually, it was originall specified as about 6 dB so that the
> range in the forward direction is assumed to be at least double
> the range in the back direction.  But again, it is only an
> indication that a given station has a favored direction, nothing
> more.

6 dB of front-to-back ratio is close enough to what you get out of
an offset-mount dipole set. This may well be more than 90% of the
cases with offset in PHG.

> > Consequently the offset or directional 
> > patterns plotted out of PHG are quite 
> > speculative and not even close to useful.
> 
> By that definition, nothing short of a full terrain mapping RF
> propogation system would be "close to useful", which is beyond
> the scope of APRS.

I have to agree with that to some amount. On the other hand, it
would be quite handy to have a PHG to gain/front-to-back/3 dB BW
tool in RadioMobile.

> HAMS have the good feel for VHF propogation and are able to use
> that knowledge to infer the general larger coverage of a higher
> station compared to a lower station, and one with a favored
> direction compared to omni's.

Some do. Many don't.

Just my thoughts, too, only meant to increase knowledge through
serious discussion :)

Benjamin OH3BK
-- 
		Live Reports from the Taxman's Paradise!



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