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[aprssig] An amusing aside (Text Pagers)

Robert Bruninga bruninga at usna.edu
Fri Jan 29 15:03:44 UTC 2010


> So we have 2 problems....
> 1)algorithmically deriving a CAP code from a callsign.

The plan would be to make the 21 bit POCSAG code equal to the 4
character callsign suffix.  There is room for 3 alpha and one
alphanumeric.  There may be some extremely rare conflicts.  But
an instantaneous check of global APRS would tell us of any
conflicts and those two people could manage it.  Besides,
messages will only appear in THEIR local RF POCSAG area and the
chance of both of them living in the same RF area is extremely
rare.

> 2)Notifying the POCSAG message server that my pager is 
> around. 

Doesn't matter.  APRS already knows where you are.  And ALL text
messages that are addressed to your callsign are converted to
your POCSAG code and transmitted out on your local POCSAG
channel. 

Ah, but what about those people who are not otherwise on
APRS?... How does APRS know where they are?  ANSWER.  Their
callsign in pre-programmed into their HT or Mobile DTMF momory.
All the user has to do is ONCE send out his DTMF memory
callsign, and APRS now knows where he is (until he moves to
another local RF area and sends out his DTMF call there).  

That was one of the main motivations of the POCSAG APRS pagers,
to give text-back capabilities to anyone with a radio.  He can
use his DTMF to send messages.  That is what we have called
APRStt. (Touch Tone).  www.aprs.org/aprstt.html

Anyway, I really think this woiuld be a fun ham radio project
and CHEAP which eveyone enjoys..

Bob, Wb4APR








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