[aprssig] APRS Cron Object Injector

Kenneth Finnegan kennethfinnegan2007 at gmail.com
Sun Mar 22 22:10:21 EDT 2015

While helping am aprx user debug an RF-gate issue this week, it came
to my attention that some users beacon objects into APRS using cron
(The Unix task scheduler). This is far from ideal, since it means
these objects are only being sent to APRS-IS and not being injected
into the actual RF LAN, but the fatal flaw I see is that none of the
cron scripts I've found online implement any form of dithering.

Even when an RF-gate is correctly configured to gate objects, since
these objects are ALL beaconed on the top of the interval, RF-gates
are dropping objects due to rate limiting.

In the ideal world we'd have users using more sophisticated daemons
than cron to beacon objects for local info, but I decided to write my
own sample script to match the cron job pattern:


To use, simply make a unique local copy of the script for each object,
open it in an editor and fill in the fields at the top of the script,
and schedule it to run at your desired interval. The goal here is to
be minimalist and easy to get people started in beaconing APRS

The script makes a good attempt at performing error checking, then
delays the beacon a random <5 minute interval to reduce the peak
bandwidth requirement for the APRS network.

Converting the script for other uses such as bulletins should be
relatively easy (just edit the OBJ_STRING definition towards the
bottom), but serious users should move to an actual APRS daemon such
as aprx (https://github.com/PhirePhly/aprx).
Kenneth Finnegan, W6KWF

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