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<div class="moz-cite-prefix">On 2/12/2022 1:44 PM, Dana Myers wrote:<br>
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cite="mid:805f2226-1be4-cd22-bcea-192522915025@comcast.net">
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<div class="moz-cite-prefix">On 2/12/2022 10:18 AM, Andrew Pavlin
via aprssig wrote:<br>
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cite="mid:1953950891.494894.1644689928184@mail.yahoo.com">
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<div dir="ltr" data-setdir="false">That was one of the reasons
for Mic-E: to have the packet take as few bits as absolutely
possible while still complying with AX.25 and still sending
something useful.<br>
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<br>
Is that really a reason for Mic-E? I thought it was to fit an APRS
encoder into a microphone,<br>
but admittedly I wasn't paying attention at the time.<br>
<br>
73,<br>
Dana K6JQ<br>
</blockquote>
<p> </p>
<p>The word ""Mic-E" (short for "Mic Encoder" ) has, over the
decades, meant three different things.</p>
<p>1) The concept of appending APRS position reports to the end of
voice transmissions, including over FM voice repeaters. The
objective was to have the shortest possible packet burst (around a
third of a second) at the end of a voice transmission that is
nearly unnoticeable before the squelch crash that follows. Hence
the data-in-address to-field kludge. <br>
</p>
<p>Part of the purpose of Mic-E was that users in organized events
would not need a second radio or channel for tracking purposes.
Further, in a busy net operation, mobile users would identify
themselves automatically to net control every time they made a
voice transmission; i.e. a form of ANI -- automatic number
identification. <br>
</p>
<p>The most advanced implementation of this was to have a TNC at the
repeater site attached to the repeater receiver. TNC DCD detect
would mute the repeat audio so the packet burst wouldn't be
repeated on the repeater output. In turn the TNC would "cross-band
digipeat" the packet burst onto the usual 144.39 APRS channel with
a separate radio. <br>
</p>
<p>For several years in the early '90s, I actually used this with a
ham volunteer fire patrol in the California mountains. I let the
packet burst go through the repeater. Anyone could monitor the
output with a radio, a TNC and an APRS program on their PC. About
that time, the first software TNCs started appearing. For those
interested in monitoring but not participating, I would setup a
Bearcat 760 scanner with it's "tape recording" jack patched into
the sound input of a PC running a soft TNC and an APRS mapping
program. Worked perfectly for people to listen to the voice
traffic and see where the patrol units were. (This was BEFORE
Internet access was ubiquitous in the Sierra foothills; i.e.
findu, etc where not an alternative.)</p>
<p><br>
</p>
<p>2) A hardware box (the Mic-Encoder) that inserted inline between
the mic and the radio. The mic cable passed through the box, so
it could sense mic PTT unkey, and fire off a packet. A kit for
this device which also had a rotary switch to select between
several canned status codes, was offered for a while by TAPR in
the early days. <br>
</p>
<p><br>
</p>
<p>3) The very compact position encoding format that placed TWO
BCD-coded decimal digits of the lat/long values into each byte of
data. <br>
</p>
<p><br>
</p>
<p>Note that the entire Mic-E functionality, including the status
reports and "tail-gating" voice transmissions, has been embedded
in all the Kenwood APRS radios from day one. <br>
</p>
<p>All the Japanese and Chinese radios that "do APRS" exclusively
use the Mic-E coding format for automatic beaconing, even if they
can't do the burst-on-unkey on voice transmissions.
"Deprecating" the Mic-E format would render virtually ALL existing
radios with built-in APRS functionality useless for APRS.</p>
<p><br>
</p>
<hr width="100%" size="2">Stephen H. Smith wa8lmf (at) aol.com <br>
Skype: WA8LMF<br>
EchoLink: Node # 14400 [Think bottom of the 2-meter band]<br>
Home Page: <a class="moz-txt-link-freetext" href="http://wa8lmf.net">http://wa8lmf.net</a><br>
<br>
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<br>
<br>
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