[aprssig] DTMF-Paging Gateway to APRS

Jason Rausch jason at ke4nyv.com
Sun Jan 25 21:40:44 EST 2009

If the spec for the full and hash DTMF strings of a callsign hasn't changed, then my little conversion program still applies:


Jason KE4NYV
RPC Electronics

--- On Sun, 1/25/09, Bob Bruninga <bruninga at usna.edu> wrote:

> From: Bob Bruninga <bruninga at usna.edu>
> Subject: [aprssig] DTMF-Paging Gateway to APRS
> To: "TAPR APRS Mailing List" <aprssig at tapr.org>
> Date: Sunday, January 25, 2009, 9:26 PM
> > Can someone define EXACTLY what this 
> > gadget needs to do?  I've already 
> > got DTMF decoder code written for the 
> > HCS08, I'm just not clear what needs 
> > to be done.  This is a duplex device 
> > that sends and receives DTMF on one 
> > channel and sends and receives APRS 
> > messages on another?
> Yes, basically.  This APRS<=>DTMF paging gateway is
> just a subset of the original APRStt gateway which used DTMF
> for user input and speech for output back to the user.
> But since these thousands of TH78's and FT51's
> already have a text display then we don't need the voice
> synthesis.  We just send APRS text data to the paging screen
> of those existing radios using the paging protocol:
> www.aprs.org/FT51-TH78.html
> The entire APRStt spec which is APRS-to-voice and
> DTMF-to-APRS has been detailed since 2001 in my APRStt docs,
> but this DTMF paging subset is much easier.  for Phase one
> there is only one DTMF user input and only a few Paging
> outputs as follows:
> PHASE 1:
> First, lets name this system as the DTMF-Paging Gateway to
> separate it from the full APRStt spec.
> USER INPUT:  There is only one user input.  That is the
> users callsign stored in DTMF memory 1.  See
> www.aprs.org/APRStt.html to see how this one key is expanded
> to a full APRS packet on receipt by the FT51/TH78 gateway.
> APRS=>PAGING OUTPUT:  There are only a few immediate
> outputs in this phase one implementation.  Recognize that
> the paging system requires a 3 digit address.  For APRS this
> paging address is "000" for all general APRS
> traffic.  For directed messages to a single station, the 3
> digit address is simply the stations callsign suffix encoded
> as digits.  APR for example is 277.
> Here are the conversions from the APRS channel to the DTMF
> paging channel.  All transmissions are to the group call of
> 000 unless noted:
> 1) Any APRS user, station, object heard direct or 1 hop
> only on the APRS channel by the gateway will cause the
> gateway to send two or more 6 byte fields as:
>    B. POSITION: ZZZ MM  (az & range to GATEWAY)
>    C. Frequency if it exists FFFFFF
>    D. remaining commment text in sextets
> Smart-word-wrapping is desired to maximize the use of the
> sextets, and avoid splitting words where possible.
> 2) Any FREQUENCY object heard on the APRS channel will
> transmit on the Paging channel two 6-byte fields:
>    A. the frequency FFF.FFFMHz  as "FFFFFF"
>    B. the Tone Tnnn as "Tnnn"
> 3) Any bulletin heard within one hop on the APRS channel
> will be converted to these sextets:
>    A.  CCCCCC - the senders call
>    B.  BLN#   - The bulletin number
>    C.  AAAAAA - the text of the bulletin
>    D.  BBBBBB - in sextets, etc
> 4) Any Messages heard on the APRS channel directed to any
> station with the suffix of XYZ will be sent as a page on the
> DTMF paging channel to the paging address of ### which is
> the DTMF hash of the callsign suffix.  For now, these are
> not stored, but are simply repeated each time the APRS
> packet is seen.
> ANYWAY I will work very closely with any volunteer to
> finalize the details of this spec for optimum compatibility
> with existing and future APRS.
> For example, how to shove a CCCCCC-SS callsign down into 6
> bytes:
> If no SSID, use full call.
> If 5 byte call and 1 digit SSID, then combine to CCCCCS
> if 4 byte call and 2 digit SSID, then combine to CCCCSS
> any other combo, then drop the PREFIX bytes to fit.
> >>> What we really need is someone to take 
> >>> on the simple task of a PIC converter 
> >>> to convert APRS messages to DTMF PAGING 
> >>> text messages so that those dozens of 
> >>> THOUSANDS of existing amateur radio 
> >>> DTMF paging HT's can be used to receive 
> >>> and send APRS messages.  
> Bob, WB4APR
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