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On 7/31/2010 12:45 PM, Matti Aarnio wrote:
<blockquote cite="mid:20100731194539.GZ8563@mea-ext.zmailer.org"
type="cite"><br>
<pre wrap="">
What? Is my APRS digipeater code wrong as it treats all WIDEn-N
constructs the same and does dupe suppression on them all?
</pre>
</blockquote>
<br>
Under the current "New Paradigm" standards, WIDE1-1 <u><b>IS</b></u>
treated differently from higher orders of N-N<br>
<br>
The whole WIDE1-1, WIDE2-1 construct was invented (it was my
proposal years ago) to work around the "brain-dead" firmware
limitations in Kantronics KPC3 TNCs. These TNCs are by far the most
widely-used piece of hardware for stand-alone digis without a
computer in the US. [It's hard to beat the simplicity and low
power consumption (15mA at 12 VDC) of a KPC3+radio digi at a remote
site.] The problem is that KPCs do dupe suppression on WIDEn-N
paths but NOT on plain RELAY or plain WIDE. <br>
<br>
On the other hand, many home users operating first-tier low-level
digipeaters (that in the past responded to "RELAY") use old TNCs
(such as PK-232s, TAPR TNC-2s, MFJ 1270s, etc) that do not have
APRS-aware firmware in them. These older devices <u>CAN NOT</u>
do n-N decremented SSIDs. <br>
<br>
With rapid APRS growth in the early '2000s, the volume of
unnecessary APRS traffic due to RELAY and plain WIDE not supporting
dupe checking just exploded. A lot of discussion followed on how
one could migrate to an exclusively WIDEn-N network (with effective
dupe control) while still allowing non-N-N-aware home fill-in
digis to remain part of the APRS infrastructure. At the same time,
one wanted to prevent home digis from acting on anything but the
very first hop of a path. <br>
<br>
The solution was the two-part WIDE1-1,WIDE2-n path I proposed. <br>
<br>
All home low-level digis set WIDE1-1 as a simple alias to be treated
as an ordinary callsign of WIDE1 with an SSID of -1. When a "dumb"
home digi hears WIDE1-1 as the first hop in a path, it digipeats it
just like any other fixed callsign, marks it as used, and passes the
second WIDE2-1 or WIDE2-2 part onward to the next tier of "real" N-N
digis. (The home digis completely ignore WIDE2-anything or higher
since only WIDE1-1 is set as an alias to digipeat on.)<br>
<br>
True high-level WIDEn-N will respond to any value of WIDEn. If a
high-level digi (that DOES have proper WIDEn-N support) happens to
hear the initial transmission, it will process WIDE1-1 as a
decremented n-N, mark it used up and hand the second half WIDE2-n to
the next (high-level) digipeater(s). <br>
<br>
<br>
The difference when monitored off the air after the first hop is
that a home fill-in digipeat of the first hop would yield<br>
<br>
WA8LMF to APRS via WIDE1-1*,WIDE2-1<br>
<br>
while a first hop captured by a "real" decrementing WIDEn-N digi,
would produce<br>
<br>
WA8LMF to APRS via WIDE1-0*,WIDE2-1 <br>
or possibly<br>
WA8LMF to APRS via *WIDE1*,WIDE2-1<br>
<br>
if the monitoring TNC's firmware treats an SSID of "zero" as
effectively no SSID at all for display purposes. <br>
<br>
<br>
The low-level WIDE1-1 home digis far outnumber the WIDE2-n "true
wides". Beaconing WIDE1-1 as the first hop from aircraft (that
have a range of hundreds of miles/km line-of-site) can potentially
trigger hundreds of home WIDE1-1 digis simultaneously, when then
ALL retransmit to the nearest true WIDEn-N systems. If the first
hop from an airborne station is a WIDE2-n only (which the home digis
just ignore) a few "true wides" rather than hundreds of home
stations will be triggered. <br>
<br>
<br>
<br>
Yes, the whole scheme is a kludge to work around the limitations of
20-year-old "clunker" TNC hardware, but it does kinda' sorta'
work.........<br>
<br>
<br>
<hr size="2" width="100%"><br>
--<br>
<br>
Stephen H. Smith wa8lmf (at) aol.com <br>
EchoLink Node: WA8LMF or 14400 [Think bottom of the 2M
band]<br>
Skype: WA8LMF<br>
Home Page: <a class="moz-txt-link-freetext" href="http://wa8lmf.net">http://wa8lmf.net</a><br>
<br>
NEW! *** HF APRS over PSK63 ***<br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/APRS_PSK63/index.htm">http://wa8lmf.net/APRS_PSK63/index.htm</a><br>
<br>
Universal HF/VHF/UHF Antenna Mounting System<br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/mobile/UniversalAntMountSystem.htm">http://wa8lmf.net/mobile/UniversalAntMountSystem.htm</a><br>
<br>
"APRS 101" Explanation of APRS Path Selection & Digipeating <br>
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/DigiPaths">http://wa8lmf.net/DigiPaths</a> <br>
<br>
<br>
<br>
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