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UI-View Bashing (was Re: APRS RF DX? (Was RE: [aprssig] APRS in Atlanta - flooding the network)

Robert Bruninga bruninga at usna.edu
Thu Oct 13 17:01:27 UTC 2005


>>> mckeehan at mckeehan.homeip.net 10/12/05 7:45 PM >>>
>I'be been looking at PHG rings (in Xastir) recently. 
>What exactly does this tell me about the network?

Who has a good VHF location and range, and who
has a poor VHF location and range.  

A digi with a
50 mile range covers almost 8000 square miles.
A digi at the local fire station with only a 40 foot
antenna may only have a 8 mile range and
only serve about 200 sq mi.  A world of difference,
which I think is valuable information to the RF user.

>My PHG circle is small, but there are digi's 
>outside of my circle that can hear me. 

Its the intersection of circles that count.  You may
have a small circle but as long as your circle
intersects a DIGI's circle then you probably can
communicate with it.

> And I can hear other stations and not be in 
>their PHG circle. Then there are some stations 
>inside of a digi's PHG circle that do not get seen 
>by the digi.

That is because back about 5 years ago, we
realized that the original way of drawing PHG 
circles were overly optimistic for mobile users
because they do not account for mobile
flutter and multipath.  APRS addendmu 1.1
changed the display of all PHG circles to HALF
(- 6dB) and calls this the default which is the
nominal range for MOBILE operation.

Your software should have two selections for
displaying PHG circles.  The default shows ranges
for mobiles, but you should be able to call up
a FIXED station PHG display which will draw
all circles to their full RF range (double for what
they show for mobiles).  You can see examples
on:

http://www.ew.usna.edu/~bruninga/aprs/aprsdos.html

So you are probably (and correctly) looking at
the PHG ranges as practical for Mobiles.  If
you select FIXED PHG display, then you will 
probably find that everyone's PHG circles
do intersect with all those stations they can hear
and work.

>It seems PHG tells you very little about a station.

Its in the eye of the beholder.  Big circles
are for stations with good VHF RF range
small circles are for stations with poor RF
range.  WIthout them all ICONS look the
same and tell the viewer nothing about the 
relative capabiliities of stations in the RF network.

People wanting to work in the RF environment
usually care about RF range and topology, 
those that just look at APRS as maps with dots 
on them on the internet usually dont.

Bob, WB4APR

On Wed, October 12, 2005 3:59 pm, Robert Bruninga said:
<snip>
> Seeing the PHG on home stations becomes valuable
> when the digi dies or is flooded out and you want
> to see who's home stations you can digipeat through
> to get from point A to B.  Usually when you are in
> this kind of circumstance, it does not work well to
> then try to ask everyone, "please now enter your PHG
> because now I need it, even though I never
> really needed it before"...
<snip>
-- 
William McKeehan
KI4HDU
Internet: mckeehan at mckeehan.homeip.net 
http://mckeehan.homeip.net 

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