[aprssig] APRS *not* SPOT

Bob Bruninga bruninga at usna.edu
Sat Sep 10 13:32:23 CDT 2011


>> ... You can go out into the boonies and beacon every minute and
>> sometimes, you will be picked up by the ISS.

> Only beacon *if* you hear other traffic.  Why beacon if 
> there are no digis within earshot...?  right?

A tree falling in the woods still makes a sound...

Years ago, On a long vacation trip through absolutely barren wilderness out
west with no digipeaters, I figured I would cut back my beacon rate to only
once every 5 or 10 minutes, and then ran with the APRS volume up so I could
hear if I ever got in range of a digi..

WRONG:  That's when I realized that when you are out of range of the APRS
infrastructure, if anything, you want to INCREASE your rate (or at least
keep it the same!).  You do not want to reduce it!.

Lesson was clear when out of nowhere I heard ONE packet.  It was another
vacationer passing me in the opposite direction (at a net crossing speed of
140 MPH).  Having heard only 1 packet, but being in simplex range for maybe
about 3 minutes (6 miles), he probably had his rate set to 3 minutes or
more.  He was out of range by the time I reacted and called and probably he
never even knew I was there (my 5 min beacon at 140 MPH) is once every 10
miles and beyond useable simplex range.

>From that experience is where the APRS PROPORTIONAL PATHING concept (built
into Kenwood and APRS radios) came about.  Mobiles (moving and actually
doing something or looking for contacts) should beacon at the 1 minute rate
simplex direct, then only every other packet attempts a 1 hop path, and only
1 in 4 attempts a 2 hop path.  This way, up-close, you get frequent updates
for finding each other, but at further distances, the load on the network is
drastically reduced.

The OTHER lesson from this expericnece was Voice ALERT and having all radios
INSERT the operators voice monitoring frequency in every packet!  (Now in
Kenwood and Yaesu radios)...

That way, we could have instantly established contact.... instead of being
two people passing each other in the wilderness and having no idea how to
make contact.

Bob, Wb4APR





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