APRS[tt] without special equipment or software
Very few hams have portable equipment for APRS but nearly everyone has a handheld radio that can send DTMF tones. APRStt allows a user, equipped with only DTMF (commonly known as Touch Tone) generation capability, to enter information into the global APRS data network.
Earlier implementations required specialized hardware and were not easily adaptable to new situations.
A new implementation does it all in software. Audio, from the receiver, is captured by the computer’s soundcard. DTMF decoding is all in software. This will run on Windows and various flavors of Linux including single board computers such as the Raspberry Pi, etc. Configuration options are very flexible so it can be adapted to a wide variety of different situations.
Success Story Using Dire Wolf and APRStt
Keith Kaiser 10/06/2015 #552
During the recent Simulated Emergency Test (SET) exercise conducted across the county, Kansas City Northland ARES successfully used APRStt to provide position information for each participant to Net Control. This was accomplished by each member checing into the net using a short APRStt Touch Tone pad entry.
The entire operation was made possible by the use of the Dire Wolf TNC software running on a Raspberry Pi. Dire Wolf, if you are unfamiliar with it is a software modem and APRS encoder/decoder. The Raspberry Pi used two inputs, one for each of the two primary repeaters being used during the SET. Each ARES member was given a two digit number, 13 for example. Each of these numbers was also assigned to the home location of the member by using latitude and longitude.
Dire Wolf has a built in macro system allowing a shortcut method of programming. By setting a TTPOINT macro variable for each ARES member they were able to show their location in just three button pushes. 13# which translates to: WA0TJT at 39.202 , -94.602.
Additional macro variables were set up for each of the other location of importance in our coverage area. For example each hospital was identified by a TTPOINT, each Shelter, each fire station and a variety of others important locations. A station could then report his/her positon at one of these by simply sending 1398#. The 13 representing the callsign, the 98 the hospital (for example) and the # to complete the APRStt entry.
Using the Dire Wolf macro facility additional capabilities were built using the APRStt basic concepts. For example it became possible for a station to identify their location by an abbreviated gridsquare. They were also able to add an APRS status code to any of the APRStt messages they wished.
Using these methods 100% of our stations (about 21) were able to give their location via APRStt and because Dire Wolf can also act as an IGate it allowed them to be posted on aprs.fi.
I want to publicly thank John, WB2OSZ for his most excellent Dire Wolf application, and Bob, WB4APR for APRStt, combined they made for a very successful SET.
References:
APRStt: http://www.aprs.org/aprstt.html
Dire Wolf: https://github.com/wb2osz/direwolf
APRStt at the West Point Triathlon
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-- See complete article in QST, July 2023, page 58
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