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Scott,</div>
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If you haven't already, be sure to upgrade the firmware in your D710 radio and control head. Kenwood release an update in 2020.</div>
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<br>
Gary<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> aprssig <aprssig-bounces@lists.tapr.org> on behalf of Scott Miller <scott@opentrac.org><br>
<b>Sent:</b> Monday, August 7, 2023 6:35 PM<br>
<b>To:</b> aprssig@lists.tapr.org <aprssig@lists.tapr.org><br>
<b>Subject:</b> Re: [aprssig] Open Source/Commercial Use acceptable APRS Alternative?</font>
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On 8/7/2023 5:46 PM, John Gorkos wrote:<br>
> I was more concerned with copy write and patent violations than with <br>
> frequency issues.<br>
><br>
> The use case is pretty straight-forward: we have a very large event <br>
> that takes place over ~3500 acres of desert. It's perfectly flat, and <br>
> about 80,000 people show up for it. The organization that runs it <br>
> uses a Kenwood trunking system for voice comms among the thousands of <br>
> people, paid and volunteer, that keep things on the rails. There are <br>
> also hundreds of utility vehicles, ranging from golf-carts to heavy <br>
> diesel fuel trucks. A non-trivial amount of radio chatter on the 25 <br>
> or so talk groups is "where are you"? Usually, that query is from a <br>
> command-and-control center (i.e. fuel truck dispatch) to a mobile unit.<br>
I think I know the event you're talking about. ;) I'll be at 5:30 & G. <br>
Look for the electric toadstool car and the multi-axis ride.<br>
<br>
Back in 2014 I helped Rampart (the field hospital) set up a custom APRS <br>
network with magnetic mount trackers on the 70 cm band. They ran at 9600 <br>
baud with quarter-second timeslots and two copies of the position packet <br>
per slot, so we were able to achieve a network cycle time of 6 seconds <br>
for two dozen vehicles. Coverage was good all the way out to where 447 <br>
winds into the hills past Empire on 500 mW. Incidentally that's where I <br>
picked up the playa name Tracker.<br>
<br>
The transmitters were consumer modules designed for the ISM band, but I <br>
bypassed part of the internal modem to keep the modulation <br>
G3RUH-compatible so my D710 (and the one at Rampart) could decode <br>
everything. It was kind of cool hearing the network go <br>
chunk-chunk-chunk..chunk-chunk..chunk non-stop with only milliseconds of <br>
dead air between active transmitters.<br>
<br>
If you'd like I can dig up the design docs and I probably have an <br>
example or two on hand. Back before COVID I was thinking about reusing <br>
the design for tracking bikes and generators that tend to wander off. I <br>
should also have some seat post mounted alarms that I was playing with, <br>
and considering cannibalizing for their housings.<br>
<br>
Also, I'm the guy behind the OpenTRAC protocol. Haven't really worked on <br>
it in ages, and there's stuff I'd want to redo if I was starting that up <br>
again. It was designed for efficiency and ease of encoding, and a lot of <br>
that is kind of unnecessary with modern hardware and it might make more <br>
sense to go with something like a binary JSON encoding.<br>
<br>
I don't see the need to run something other than APRS for what you're <br>
describing. The protocol has been used for all sorts of non-ham stuff <br>
for decades, just not with the trademark attached.<br>
<br>
I just pulled the D710 out of my trailer after having it in there for a <br>
dozen years since I haven't fired it up during the week in years and <br>
figured it might get more use in the cab of the truck. I'm unlikely to <br>
be on the air during the event unless I've got a specific need to be. <br>
I've got enough technical projects to keep me busy.<br>
<br>
Scott<br>
N1VG<br>
<br>
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