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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 |
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