[aprssig] Advice required on a possible digipeater function

Chris Moulding chrism at crosscountrywireless.net
Sat Feb 21 14:33:42 CST 2009


Over the past few months I've been working on an APRS TNC/Digi/Tracker 
based on the original TNC design by Bob Ball WB8WGA.

The plan is to produce a TNC that will work as a fill-in digipeater and 
mobile tracker that can also be used with UI-View or WinPack in a fixed 
or portable station. The current progress of the project is detailed on 
my webpage: http://www.crosscountrywireless.net/aprs_tnc.htm

One possible feature I'm looking at adding to the firmware is an 
addition to the usual fill-in digipeater function. In this function 
(laughingly called "Superdigi" for discussion purposes) ANY valid alias 
received apart from WIDE2-1is digipeated with WIDE2-1 for an additional 
single hop. WIDE2-1 would be digipeated with a callsign substitution.

For example:
MB7UBN>APRS,WIDE3-3 would be digipeated as MB7UBN>APRS,WIDE2-1 by the 
first digipeater using "Superdigi" and as MB7UBN>APRS,G4HYG* by a second 
digipeater using "Superdigi"(assuming mycall is G4HYG).

I can think of three uses for a digipeater with this function:

1) The first is for emergency use on a separate RF channel to the usual 
APRS channel where a digipeater is needed to digipeat all APRS aliases 
that turn up on an event or emergency callout. (In the UK they could be 
RELAY, TRACEn-n, WIDE1-1, WIDEn-n, RAYNET or TEMP). The use of a few 
digipeaters with this function on a separate RF channel could also act 
as a simple "plug and play" APRS mesh network.

2) It would allow a station located on the edge of existing VHF APRS 
coverage to digipeat all stations heard to an igate via an intervening digi.

3) It could be used to digipeat all ISS traffic on 145.825 MHz to the 
local terrestrial APRS channel.

I know that in areas where existing full digipeaters operate it could 
have the effect of stopping digipeater hops but in that situation the 
TNC should be used as a conventional fill-in digipeater with WIDE1-1 as 
an alias.

To me it seems like a good idea but I would welcome feedback from 
existing sysops on what I should do.

Should I include this option in the TNC?

Should I forget about the option? I've not released the firmware yet 
just in case there is a problem I've not thought about.


Chris, G4HYG (MB7UBN APRS igate and full digi)

Chris Moulding
Cross Country Wireless (2009) Ltd
7 Thirlmere Grove, Bolton, Lancs, BL4 0QB, UK
Tel/fax: +44(0)1204 410626
Mobile:  +44(0)7752 391908
Website: http://www.crosscountrywireless.net
Registered company number 6780346 

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