[aprssig] Omni DFing...

[Robert Bruninga]

>I don't get it.
>I don't understand at all what that has to do with 
>my power output nor how APRS fits in the picture 
>except as a way to do the mapping.

PHG is a field that is supposed to be in all APRS fixed
position reports that includes your stations power,
antenna height, antenna gain, and any directivity.
APRS uses this station performance info to display 
approximate relative  coverage range for each station.

Viewing a map with these contours gives one an easy
view of the relative performance of each station and
therefore a way to visualize the network and how
to build a path if needed.

For DFing, The Power digit is replaced with a signal
strength report.  Now then your station's position
includes its Antenna Height, Gain and Directivity and
now signal strength heard.  APRS uses that knowledge
to plot signal strength contours so tht it is easy
to visualize the probable location of the unknown
signal using nothing but these signal reports. See;

http://www.ew.usna.edu/~bruninga/dfing.html

The most striking thing is the great contribution 
from ZERO signal reports which plot as dark areas
showing where the signal IS-NOT.  Normal DFing
with beams requires:
1) People with Beams     (1% of users)
2) People that can hear the signal  (3% of users)

Now, with APRS OMNI-DFing, you get:
1) Data from ANYONE with a radio (100% of users)
2) Data from EVERYONE (100%).

Notice the TWO ORDERS of magnitude more data
you get when you need to locate an unknown signal.
>From day one, Signal Location was one of the
main applications of APRS, though many of the
clone softwares did not include it.

So only 1 digit in your PHG has anything to do with
your power.  The other 3 quantify your station's
propogation performance which is *very important
information* in an RF network (APRS).

Hope that helps.
Bob, WB4APR


On Thu, 2006-05-11 at 18:17 -0400, Robert Bruninga wrote:
> >>> jdw at eng.uah.edu 05/11/06 10:35 AM >>>
> >The DF plot web page has a May 9 date.  It's been 
> >2 days and no one has pulled out an Arrow or 
> >swung a beam around to get an actual bearing?
> 
> Yep, welcome to the real world of trying to get
> ham radio operators to do routine DFing.  That is
> exactly why we think that APRS with omni signal
> strength plotting has so much more potential.
> 
> With signal strength reporting, 100% of everyone
> with a radio can give an input from anywhere at
> any time with his mobile, or HT or base station
> or whatever.  AND, -not-hearing-it at one's location
> is just as valuable a report as hearing it.
> 
> Waiting for the guys with beams is some times
> too long.  And many times not worth the trouble
> for routine traking down occasional signals.
> 
> >Omni DFing, APRS or otherwise, is fine if that's 
> >all you've got, but the directional gear should be 
> >out by now...
> 
> Maybe, maybe not.  If we call up those guys
> for every little erroneous signal, they get burned
> out..  Better to localize the source to about a mile
> or so with ploting DFS signal reports first, so that
> then you know where to send the DF hounds
> next time the signal is heard.
> 
> See the new reports plotted today...
> http://www.ew.usna.edu/~bruninga/dfing.html 
> 
> Just need one person, anyone with a radio and
> ears in Woodbridge to give a signal report and
> that should get us closer...
> 
> Bob, WB4APR
> 
> 
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