Mobile APRS trackers, from Baker to Vegas 1995

This is the chronicle of what we did the first year, when APRS was new, and we were some of the pioneers. Later, in 1996, we would expand the effort to include 17 mobile units, mixing a variety of radios and TNCs ad GPS receivers, pushing the limits yet again.

In 1995, each vehicle had a 2-piece power harness...in retrospect, the fuses should have gone under the hood of the vehicle, rather than back in the package. Fortunately, there were no wire fires because of this oversight.

The main harness was built from the radios DC power cable, which had the 2 in-line fuses built in. This was equipped with the female Molex(*) for the "battery end". The GPS module connector served as the common point for the leads for TNC and Radio Power as well. This harness was built to be four feet long, from "battery end" to the GPS connector, with 12" leads from the GPS connector to the TNC and Radio connectors.

The second harness was built, as needed, to connect from the vehicles battery, to reach the main harness. These pieces were up to 10 feet long.

The intention was to have the APRS "equipment package" mounted in the trunks of the vehicles, running unattended, while a voice operator operates inside the passenger compartment.

* This polarized Molex connector has been proposed as a standard as the basic connector for 12 VDC emergency equipment for ARES equipment by the ARRL, and it has been accepted here in the Silicon Valley Section, as well as most of the East Bay Section.

The GPS receiver data output of the Trimble SVEE-6 is a DB-9. Following the WB6APR recommendation, we used a DB-9 connector coupled to a mono-1/8" male mini-phone plug.


On the back of the TNC, we installed an adapter with a female mono 1/8" mini-phone jack, mounted to the shell of a DB-25 connector. The jack is wired to the DB-25 male connector as shown below.

Front View of the Alinco - AEA - Trimble package

Rear View of the Alinco - AEA - Trimble package

We used separate power connector for the radio and the GPS receiver, to ensure that the high-current connector was connected to the radio.

These collections of radio, TNC, and GPS were strapped together using nylon wire ties. We then suspended them with loose wire ties within a large Tupperware-style tub. Holes cut into the plastic housing gave us the ventilation we needed, and gave us paths for our power and RF cables, while providing the support for the wire ties. This "package" then also provided a method for reducing the shock and vibrations of mobile operation for the equipment.

The voice radios used by the operators were sometimes strapped to the back of the drivers seat, or supported by window struts. Wooden or plastic cutting boards also provided sturdy platforms for mobile brackets, and could rest on the operators laps.