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[aprssig] APRS Antenna Bearing and mirowaves

Robert Bruninga bruninga at usna.edu
Fri Nov 14 17:41:49 UTC 2008


Antenna Bearing for APRS:

I was approached by some microwave experimenters looking to use
APRS for antenna alignment between stations.  I recommended the
following format:

HEADER:  CALLSIGN>APMEPx,WIDE1-1:

=DDMM.mmN/DDDMM.mmW\CSE/SPD/BRG/NRQ/FFF.FFFMHz ATV-MEP 

You will recognize this as the DF BEARING report format.  The
advantage of using this format is that all APRS clients already
should plot these antenna bearings on the map, and no one is
using the DF bearing format as much as we had hoped years ago.

Where BRG is the antenna bearing 001 to 360
Where NRQ is 3 digits....  Set N=9
Where  R  is Range encoded as R^2 (4=16mi etc)
Where   Q is Quality or  beamwidth.
9 = 1 degree wide
8 = 2 degree
7 = 4 degree
5 = 8 degree
4 = 16 degree
3 = 32 degree
2 = 64 degree
1 = 128 degree
0 = OMNI

I am surprised that I cannot find NRQ defined in the APRS SPEC.
(Maybe I didn't look hard enough) So I went back to my original
docs PROTOCOL.TXT and DF.TXT but even they did not document the
Q byte.  Ill fix that by adding this to the APRS1.1 addendum.

Of course FFF.FFFMHz is too small for microwave, but the Freq
spec has defined additional characters so we have well defined
formats for microwave.

A96.000MHz would be 1296 MHz
B20.000MHz would be 2320 MHz
C01.000MHz would be 2401 MHz 
D01.000MHz would be 3401 MHz
E51.000MHz would be 5651 MHz 
F60.000MHz would be 5760 MHz 
G30.000MHz would be 5830 MHz
H01.000MHz would be 10,101 MHz
I01.000MHz would be 10,201 MHz
J68.000MHz would be 10,368 MHz 
K01.000MHz would be 10,401 MHz
L01.000MHz would be 10,501 MHz
M48.000MHz would be 24,048 MHz 
N01.000MHz would be 24,101 MHz
O01.000MHz would be 24,201 MHz
Etc

Thanks
Bob, WB4APR




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