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[aprssig] BRRRAAAPS and listening

Bob Bruninga bruninga at usna.edu
Fri Oct 21 14:27:33 UTC 2011


Sometimes I get the feeling that few people listen to the APRS channel now
and then to hear what is going on.  There is a lot to be learned just by
listening.

For example..  If you hear

BRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRAAAAAAAAAAAAAAAAAP

You are hearing a 50% wasted channel, because all the BRRRRRR's at the
beginning are just TXD delay.  The AAAAAP on the end is the actual APRS
data. The data in an APRS Mic-E packet lasts typically 1/2 second.  If the
TXD is 500 ms, then channel capacity in THAT ENTIRE AREA is suffering a 50%
loss in channel capacity.

Typically, we can operate with TXD's of about 150 ms.  PLEASE everyone,
listen in your area and fix any digipeater that is blathering all this
wasted bandwidth!

This also applies to your own station.  Kenwoods used to come with a default
of 500ms which was unbelievably long.  Please check your settings and
permanently re-configure to 200 or 150 ms.

A packet should sound more like:

BRRRRAAAAAAAAAAAAAAAAP

But the most important setting is the DIGIPEATERS!  Because they impact
EVERY SINGLE PACKET in the area.  Fixing them with minimum TXD can have a
nearly doubling of channel capacity.  Fixing one LID's mobile setting is
only going to change the area load by 1%...

FIX THE DIGIS.  And also make sure they are providing the local area
repeater frequency object in the local area as well while you have the
SYSOPS attention...

Bob, WB4APR




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