[amsat-bb] APRS tracking on 145.825

Bob Bruninga bruninga at usna.edu
Fri Jan 16 07:23:37 PST 2009

Answered on the AMSAT BB in case others have similar concerns.

> ...am still trying to get out with vy 
> little success, my station is the only 
> 24/7 station within 200sq miles!
> [in Europe].
> I have set SmartBeaconing (ideal for 
> conserving band space) and am on ARISS 
> on 145.825 simplex how can i ensure
> that my sigs are picked up and reported 
> to APRS-IS.

First of all, Smart Beaconing is not really a bandspace conservation mechanism, but is more like an exact-track-assurence algorithm.  It tries to make sure that your position reports reflect all turns throughout your travels and then a lower rate on straight stretches.  Yes, it is better than transmitting every 30 seconds forever (to get a good track) but when one is maneuvering around in the city and mall parking lot, it can be a network hog due to all the turns.  It makes no sense via an occasional satellite to be using an algorithm designed for optimum track-history.

APRS was never designed or intended to be a TRACKING system, and certainly does not have the bandwidth to give everyone a precise track.  On the contrary, APRS is a communication network between amateur radio operators, not a vehicle tracking system.  THe purpose of your position beacon on APRS is to let fellow net participants know approximately where you are for the purpose of COMMUNICATIONS.  One report every several minutes is fine.

Via satellite, only one report per pass is expected, maybe two for reliability, to assure you are indicated as active.

Hence, a fixed rate just updating  your approximate location periodically is all that is required.  For terrestrial APRS netowrk the best algorithm then is PROPORTIONAL PATHING.  It maintains a low, but fixed rate, direct, and sends packets via 1 hop only half the time, via 2 hops only 25% of the time thus maintaining good network accountabilty to other users close in, while reducing netowrk load at a distance.  Ths algorithm is built into the new D710 APRS radio.

For reporting in from the wilderness via satllite (say PCSAT-1), the only path that works when PCSAT-1 is in default mode is VIA W3ADO.

The path via WIDE1-1 will not work via PCSAT-1, W3ADO-1 or the ISS.  Well, it will work via ISS, but the www.ariss.net web page will not capture it, because the ISS does not do callsing substitution when that path is used.  Therefore the APRS-IS system will not recognize it has having been digipeated via the ISS, though it will show up on other FINDU pages.

For attended uplink on 145.825 from wilderness areas, for mobiles, a rate of once every 2 minutes is receommended.  For mobiles in-motion, actively operating a pass, a rate of 1 minute is acceptible.

Good luck
Bob, Wb4APR

>   As wide1-1 is an alias to ariss i see no point in
>   path alteration, just change of qrg. How does that
>   sound to you?
>   --
>   --
>   Best wishes/Meilleurs sentiments/51/73

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