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General
Information is relayed around a APRS RF network using packet radio digipeaters. To make use of these digipeaters you need to specify an unproto which invokes these digipeaters. APRS defines generic digipeaters such as RELAY, WIDE, TRACEn-n and WIDEn-n
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Generic WIDEn-n
Unproto Example -> APRS,WIDE7-7
- 1st Digi -> APRS,M0AAA*,WIDE7-6
- 2nd Digi -> APRS,M0AAA*,M0BBB*,WIDE7-5
- 3rd Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,WIDE7-4
- 4th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,WIDE7-3
- 5th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,WIDE7-2
- 6th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE7-1
- 7th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,M0GGG*,WIDE7*
Advantages:
Allows plotting of digipeater paths and digi coverage maps. Reduces QRM because the digipeater adds it's callsign to the list ensuring that digipeater does not relay this particular packet again Makes it easier for APRS messaging to determine a return path
Disadvantage:
Makes a packet frame larger and more prone to errors
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Generic GBRn-n
Unproto Example -> APRS,GBR7-7
- 1st Digi -> APRS,GBR7-6
- 2nd Digi -> APRS,GBR7-5
- 3rd Digi -> APRS,GBR7-4
- 4th Digi -> APRS,GBR7-3
- 5th Digi -> APRS,GBR7-2
- 6th Digi -> APRS,GBR7-1
- 7th Digi -> APRS,GBR7*
Advantage:
Keeps packet frame to the same size as the initial transmission consequently often travels further
Disadvantage:
Causes alot of QRM as digipeaters have a hard time telling if they have already digipeated this transmission so often digipeat more than once. The use of a checksum on the packet does ease this although if the packet is heard again after the specified amount of dupe time has expired it will be digi'ed again
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Generic WIDEn-n then GBRn-n
Unproto Example -> APRS,WIDE6-6,GBR7-7
- 1st Digi -> APRS,M0AAA*,WIDE6-5,GBR7-7
- 2nd Digi -> APRS,M0AAA*,M0BBB*,WIDE6-4,GBR7-7
- 3rd Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,WIDE6-3,GBR7-7
- 4th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,WIDE6-2,GBR7-7
- 5th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,WIDE6-1,GBR7-7
- 6th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7-7
- 7th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7-6
- 8th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7-5
- 9th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7-4
- 10th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7-3
- 11th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7-2
- 12th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7-1
- 13th Digi -> APRS,M0AAA*,M0BBB*,M0CCC*,M0DDD*,M0EEE*,M0FFF*,WIDE6*,GBR7*
Advantage / Disadvantage
This is like a bit from column A and bit from column B. As you can see there is alot of digipeaters used here. Not forgetting of course this is a linear example, in reality your transmission would digipeat out in a spider type fashion and consequently should not be used