[aprssig] Open Source/Commercial Use acceptable APRS Alternative?

n6lrv at outlook.com n6lrv at outlook.com
Mon Aug 7 23:38:04 EDT 2023


If you haven't already, be sure to upgrade the firmware in your D710 radio and control head. Kenwood release an update in 2020.


From: aprssig <aprssig-bounces at lists.tapr.org> on behalf of Scott Miller <scott at opentrac.org>
Sent: Monday, August 7, 2023 6:35 PM
To: aprssig at lists.tapr.org <aprssig at lists.tapr.org>
Subject: Re: [aprssig] Open Source/Commercial Use acceptable APRS Alternative?

On 8/7/2023 5:46 PM, John Gorkos wrote:
> I was more concerned with copy write and patent violations than with
> frequency issues.
> The use case is pretty straight-forward:  we have a very large event
> that takes place over ~3500 acres of desert.  It's perfectly flat, and
> about 80,000 people show up for it.  The organization that runs it
> uses a Kenwood trunking system for voice comms among the thousands of
> people, paid and volunteer, that keep things on the rails.  There are
> also hundreds of utility vehicles, ranging from golf-carts to heavy
> diesel fuel trucks.  A non-trivial amount of radio chatter on the 25
> or so talk groups is "where are you"? Usually, that query is from a
> command-and-control center (i.e. fuel truck dispatch) to a mobile unit.
I think I know the event you're talking about. ;) I'll be at 5:30 & G.
Look for the electric toadstool car and the multi-axis ride.

Back in 2014 I helped Rampart (the field hospital) set up a custom APRS
network with magnetic mount trackers on the 70 cm band. They ran at 9600
baud with quarter-second timeslots and two copies of the position packet
per slot, so we were able to achieve a network cycle time of 6 seconds
for two dozen vehicles. Coverage was good all the way out to where 447
winds into the hills past Empire on 500 mW. Incidentally that's where I
picked up the playa name Tracker.

The transmitters were consumer modules designed for the ISM band, but I
bypassed part of the internal modem to keep the modulation
G3RUH-compatible so my D710 (and the one at Rampart) could decode
everything. It was kind of cool hearing the network go
chunk-chunk-chunk..chunk-chunk..chunk non-stop with only milliseconds of
dead air between active transmitters.

If you'd like I can dig up the design docs and I probably have an
example or two on hand. Back before COVID I was thinking about reusing
the design for tracking bikes and generators that tend to wander off. I
should also have some seat post mounted alarms that I was playing with,
and considering cannibalizing for their housings.

Also, I'm the guy behind the OpenTRAC protocol. Haven't really worked on
it in ages, and there's stuff I'd want to redo if I was starting that up
again. It was designed for efficiency and ease of encoding, and a lot of
that is kind of unnecessary with modern hardware and it might make more
sense to go with something like a binary JSON encoding.

I don't see the need to run something other than APRS for what you're
describing. The protocol has been used for all sorts of non-ham stuff
for decades, just not with the trademark attached.

I just pulled the D710 out of my trailer after having it in there for a
dozen years since I haven't fired it up during the week in years and
figured it might get more use in the cab of the truck. I'm unlikely to
be on the air during the event unless I've got a specific need to be.
I've got enough technical projects to keep me busy.


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