[aprssig] Beacon rate feedback

Scott Miller scott at opentrac.org
Mon Nov 24 01:15:26 EST 2008

I drove about 600 miles up to my sister's place in the San Francisco
area and back this weekend, and used the drive as an opportunity to try
a few things.

I was running an FC-301/D at 5 watts, which is a lot less power than
what I usually run on the DR-135T.  But this time, I set the beacon
interval to 30 seconds and the NICE parameter on the T2 (a prototype of
the add-on board for the FC-301/D) to 3.

The NICE parameter (named for the UNIX command for setting process
priority) causes the T2 to skip the specified number of beacons whenever
it hears itself digipeated.  I've never run it higher than 1 in normal
operation, and never with a significantly higher than normal beacon rate.

With the 30/3 setting, as long as it gets an echo, the beacon interval
is effectively 2 minutes.  If it didn't hear anything, it'll retry every
30 seconds.

This is a higher rate than I'd run for everyday use, but I don't make
these trips often and I wanted to gather some useful data.  And so far
it looks like it worked pretty well - there are very few places where
more than one packet in two minutes was seen at an IGate, and some of
those (like in Salinas) were heard by an IGate without hitting a digipeater.

For highway driving at least, I think I like this scheme better than
SmartBeaconing.  It retries in places where it's needed and doesn't
flood the network.  Whether this would still be a good idea at 50 watts,
I'm not sure.  But I figure at 5 watts, the chances are very good that
if the digipeater can hear me, I can hear it at least as well.

I know the HamHUD has a digi-meter to tell you when you're getting in,
and I think APRSDOS had some kind of feedback, but I can't recall if
either of those actually controlled the transmission rate that way.
Does anything else do this?  It's something that the T2's been able to
do for a while now, but I haven't really been pushing the feature.  I'd
like to encourage greater use of it, but I'd like to hear what the APRS
community thinks of it.  The callsign in use was N1VG-6 if you want to
check it out.



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