In article , Jack Twilley
writes
[This message was reposted from eHam.net's APRS forum by the author]

I'm writing an APRS client in Ruby, so I've spent a lot of time
staring at packets. I think I understand how RELAY works -- whatever
station repeats RELAY packets replaces RELAY with their callsign. WIDE
works the same way, but what about WIDEN-n? I've collected some
packets with my AEA TNC to demonstrate my confusion.

Callsign substitution when using RELAY and WIDE is probably not the
norm.

KE6STHW6CX-3*WIDESWRRSR:'1PQ!68k/]"4%}Sione
KE6STHW6CX-3W6CO-5*SWRRSR:'1PQ!68k/]"4%}Sione

In this case, WIDE is being replaced with W6CO-5 when that station
repeats the packet. That makes perfect sense.

K6HG-9*WIDE2-1S7RURP:'2]1l sk/]"3q}
K6HG-9WIDE2*S7RURP:'2]1l sk/]"3q}

What station is repeating this packet? I can't tell. What's supposed
to happen here?

There are two implementations of WIDEn-N -

1. (In Kantronics UIFLOOD terminology, this is ID.) The digipeating
station decrements the SSID of the WIDEn-N alias, inserts its own
callsign/alias, with the 'H' bit set, before the WIDEn-N, and removes
any previous alias immediately before the WIDEn-N. The idea being that
the callsign/alias of the last digipeater is shown. So, if DIGI1 and
DIGI2 are two digis supporting WIDEn-N, and G4IDE sends a frame via
WIDE3-3, you get this -

G4IDEAPRS,WIDE3-3:Hello world
G4IDEAPRS,DIGI1*,WIDE3-2:Hello world
G4IDEAPRS,DIGI2*,WIDE3-1:Hello world

2. (In Kantronics UIFLOOD terminology, this is NOID.) The digipeating
station decrements the SSID of the WIDEn-N alias, it does not insert its
own callsign/alias, or remove any previous alias. So, if DIGI1 and DIGI2
are two digis supporting WIDEn-N, and G4IDE sends a frame via WIDE3-3,
you get this -

G4IDEAPRS,WIDE3-3:Hello world
G4IDEAPRS,WIDE3-2:Hello world
G4IDEAPRS,WIDE3-1:Hello world

Mixing the two can result in misleading information.

--
Roger Barker, G4IDE -
For UI-View go to - http://www.UI-View.com
For WinPack go to - http://www.peaksys.co.uk