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[aprssig] Re: Interference on 144.390

Robert Bruninga bruninga at usna.edu
Thu Mar 9 03:25:31 UTC 2006


>As of midnight Tuesday night... there is a repetitive 
>continuous data signal on 144.390, causing severe 
>disruption...Can anyone with 2m beams please DF it...
>
>I've got it S9 on a discone at 145 feet in McLean...
>It is... S9 on an omni antenna in Sterling, and ...
>heard at S4 near theintersection of Rt28 and Rt50.

Entering that data into APRSdos yields a solution probably
at Dulles Airport.  Took me 2 minutes tops.  To see the
APRSdos plot, see:
http://www.ew.usna.edu/~bruninga/aprs/DFinVA.GIF

This stuff was fundamental to the design of APRS
since all APRS stations are supposed to have their
antenna-height-gain included in their fundamental
position reports (except for UIview).  From this, APRS
knows the range of your receiver and can plot overlaping
signal contours inversly proportional to signal.  The
point near the edges of intersecting brighter colors
is the location of the signal.

If we could just get people to listen and make signal 
reports on any signal.  Even if you do not hear it,
THIS IS VALUABLE.  it instantly BLACKS OUT all the
area around you where the signal cannot be.  THis
very rapidly eliminates more area usually than "heard"
reports contribute.  There are no "negative" reports
shown here, but believe me, they are very valuable
since you usually get moer of them that actual
heard reports.  but the ALL contribute to the picture.

APRS has all this built in.  I am saddend that this 
fundamental aspect of APRS was left out of most 
follow-on APRS clones...

de Wb4APR, Bob






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