Saturday, July 31, 2010

History and Working of Wide1-1,WideN-1

Under the current "New Paradigm" standards, WIDE1-1 IS treated differently from higher orders of N-N

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.

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 CAN NOT do n-N decremented SSIDs.

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.

The solution was the two-part WIDE1-1,WIDE2-n path I proposed.

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.)

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).

The difference when monitored off the air after the first hop is that a home fill-in digipeat of the first hop would yield

WA8LMF to APRS via WIDE1-1*,WIDE2-1

while a first hop captured by a "real" decrementing WIDEn-N digi, would produce

WA8LMF to APRS via WIDE1-0*,WIDE2-1

or possibly

WA8LMF to APRS via *WIDE1*,WIDE2-1

if the monitoring TNC's firmware treats an SSID of "zero" as effectively no SSID at all for display purposes.

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.

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.........


Stephen H. Smith wa8lmf (at)
Home Page:

NEW! *** HF APRS over PSK63 ***

Universal HF/VHF/UHF Antenna Mounting System

"APRS 101" Explanation of APRS Path Selection & Digipeating

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