Some day with the second wave of APRS enthusiasm in Finland our group started thinking about using the built-in 1200 bps AFSK modem of the popular Nokia R58 equipment for position reporting. The first evaluations showed that the MPT1327/1343 modem (CML FX429) can't transmit AX.25 frames. We decided to develop a protocol for amateur radio position reporting over Band III modems found in many European surplus analog trunking radios like Nokia R58, Philips FM1200 and Ericsson 705 series. The protocol has been developed so that also many NMT450 and NMT900 phones can be adapted to MPRS.
MPRS™ uses the APRS™ concept by Bob Bruninga, WB4APR, for amateur radio position reporting. MPRS™ equipment can be connected to existing APRS™ infrastructure through an RS-232 port. MPRS™ equipment is compatible with current APRS™ software like XAstir, UIView etc.
The current Nokia R58 MPRS station can be configured for a mobile tracker with a GPS receiver, a fixed station or a stand-alone digipeater.
The tracker communications have been adapted from the Mic-E protocol. The position report is compressed for a burst length of only a tad over 100 milliseconds. The tracker can send stand-alone position reports on a defined channel or just add an AFSK burst after a speech transmission. The mobile unit shows the callsign and Maidenhead locator of the last heard station.
NMEA-0183 position information is connected to the SIO pin 13 of the R58 mobile (NB! The input is TTL level, most GPS receivers need level conversion from RS-232!).
The fixed station has the coordinates programmed in the radio. The fixed station can send stand-alone position reports on a defined channel or just add an AFSK burst after a speech transmission. The radio unit shows the callsign and Maidenhead locator of the last heard station.
The fixed station can be connected to a computer with an APRS ™ software (a MBUS-RS-232 converter is needed).
A Nokia R58 series mobile can be configured to operate as a stand-alone MPRS™ digipeater. It will repeat MPRS™ position report packets it hears. An R58 radio can also configured as a gateway to transmit MPRS™ packets from a repeater output frequency to the MPRS™ network and the APRS™ network.
NB! This mode does not function yet
APRS™ is a trademark of Bob Bruninga, WB4APR
MPRS™ is a trademark of Moppeakatemia