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I've mentioned it before, but I deployed a couple dozen custom
trackers for ambulances at Burning Man a couple of years ago. They
were built on 440 MHz ISM transmitters at 1/2 to 1 watt, with 9600
baud FSK that was compatible with the TH-D710 we used for the base
station.<br>
<br>
The TX/RX switching time was short enough that we were able to get 4
timeslots per second, and each position packet was transmitted twice
within a timeslot, for a total of 8 packets per second and a network
cycle time of 6 seconds. Never seen a D710 that busy before.<br>
<br>
Our goal was to have reliable tracking with the 5-mile extent of the
city, but we got solid tracking out to at least 15 miles, where the
highway started to wind into the hills at Empire. The Black Rock
Desert is a nearly ideal environment, though - not counting the
ridiculous amount of radio activity across multiple bands, and the
Flaming Lotus Girls using three dozen stun guns as spark gap
igniters for flame effects on some giant mechanical snake thing.<br>
<br>
Any next-generation APRS system really needs careful attention to
channel access control. ALOHA just doesn't cut it for high
performance. Manual GPS timeslot assignment requires too much
manual coordination. We need smarter nodes.<br>
<br>
A radio network simulator would be a very useful thing to have. I
made something fairly primitive for the purposes of developing a
special-purpose mesh networking protocol a few years ago - it'd let
you drag nodes around the screen, each with a range circle, and
nodes would either be within range of each other or not. I'd love
to have a program that simulated dozens or hundreds of nodes, some
of them moving, with separate transmit and receive ranges and a
simple model for noise and interference.<br>
<br>
With a framework like that in place, you could test node software by
prototyping in something like Python and run lots and lots of
accelerated simulations and generate statistics on network
efficiency.<br>
<br>
Scott<br>
N1VG<br>
<br>
<div class="moz-cite-prefix">On 6/13/2016 4:33 AM, Ev Tupis via
aprssig wrote:<br>
</div>
<blockquote
cite="mid:1358176562.2034781.1465817629411.JavaMail.yahoo@mail.yahoo.com"
type="cite">
<div style="color:#000; background-color:#fff; font-family:Courier
New, courier, monaco, monospace, sans-serif;font-size:16px">
<div id="yui_3_16_0_ym19_1_1465816905815_6481" dir="ltr">The
lower the frequency, the greater susceptibility to
constructive and destructive multipath jitter. This is the
reason that there aren't many "low channel" TVWS (TV White
Space) successes today. This is also the limiting factor to
adopting high-speed data at 2 meters.</div>
<div id="yui_3_16_0_ym19_1_1465816905815_6458" dir="ltr"><br>
</div>
<div id="yui_3_16_0_ym19_1_1465816905815_6459" dir="ltr">400 and
900 MHz ISM data modules are interesting...if only there was a
10-watt amplifier that could be applied for use in the amateur
services. That would / could change alot.</div>
<div id="yui_3_16_0_ym19_1_1465816905815_6483" dir="ltr"><br>
</div>
<div id="yui_3_16_0_ym19_1_1465816905815_6484" dir="ltr">Ev,
W2EV</div>
<div id="yui_3_16_0_ym19_1_1465816905815_6485" dir="ltr"><br>
</div>
<div id="yui_3_16_0_ym19_1_1465816905815_6436"><br>
</div>
</div>
<br>
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<br>
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</pre>
</blockquote>
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