APRS DTMF-to-APRS PROTOCOL                               23 Mar 2010
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                                                              WB4APR

23 Mar 2010 Updated to new  formats
10 Oct 2002 Original

APRStt is the specification for Touchtone applications of APRS.  It
allows anyone with an HT to use his DTMF pad to enter APRS positions,
messages and other data.  Thus EVERYONE in ham radio can communicate
by APRS, not just those with APRS HT's.

Although the Terrestrial application of APRStt with its well defined 
voice repsonses will revolutionize APRS and allow everyone to parti-
cipate, a shortend modified version is necessary for Satellite 
applications.  Due to congestion on the uplink, the entire data from 
one station must be sent in a single burst.  This is done by pre-
loading the position and call in two DTMF memories and keying them
consecutively.

Therefore the following SPACE version of APRStt is being developed:

FUNDAMENTALS: 
 1) Protocol must fit into 16 digits (typical DTMF memory size)
 2) Protocol must end with the "D" key
 3) Calls are HASHED, meaning a 6 digit decimal callsign equivalent. 

The best small satelllite application of SPACE APRStt is to have a simple
DTMF decoder on the satellite uplink and then for the satellite to
convert the DTMF to the SPACE-APRStt equivalent AX.25 packet on the
downlink.  Then all APRS stations in the footprint of the satellite and
the worldwide APRS internet linked system of AX.25 receivers will 
receive the data.  If the satelltie is DTMF only, then all it has to do
is regenerate the DTMF on the downlink and let a SPACE-APRStt ground
station convert the packet for injection to the worldwide APRS internet
system.  FOllowing are the initial definitions of SPACE-APRStt formats:

POSITION FORMAT:  The following is the proposed 
 
16 digit DTMF     Packet
----------------  ---------------------------------------
BhaaaoooAccccccD  cccccc>APxxxx,WIDE:=AAA0.00N/hLLL0.00W$
 
Where B begins the Position format
Where h is the hemisphere region (see table)
Where aaa are the 3 MSB digits of Latitude
Where ooo are the 3 MSB digits of Longitude (not counting hundreds)
Where A begins the Callsign digits
Where cccccc are the callsign digits (924277=WB4APR)

The Hemisphere digit is:
1 = N lat, E long (Europe region 1 to 99 East longitude)
2 = N lat, W long (North America to 99 west longitude)
3 = N lat, E long (Asia, Pacific Rim > 100 East Longitude)
4 = S lat, W long (South America to 99 W longitude)
5 = S lat, E long (Africa to 99 E longitude)
6 = N lat, W long (North America > 100 W longitude)
7 = S lat, W long (South Pacific > 100 W longitude)
8 = S lat, E long (Australia > 100 E longitude)

MESSAGE EXAMPLE:
 
16 digit DTMF     Packet
----------------  ---------------------------------------
C1234567AccccccD  CCCCCC>APxxxx,WIDE::ALL      :1234567
 
Which is a message to ALL from cccccc containing a 7 digit
message.  I have defined MANY pre-defined messages including
ARRL radio grams etc...  so this is not much of a
limitation...

We can publish the list of messages when this gets implemented..

Bob, Wb4APR