Argent Data Systems
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programs exist, using either the APRS radio network, the APRS-IS, or both. Some of these
programs can function as IGates as well.
Connected to the worldwide APRS-IS stream are a number of database services. These systems
(aprs.fi and openaprs.net are two of the most popular) process and store all APRS traffic that
finds its way to an IGate anywhere in the world, and most provide maps, weather displays, and
telemetry graphs based on this traffic. This allows anyone with Internet access to monitor APRS
data without needing radio equipment of their own or special software.
Getting data to a web-connected database isn’t the only thing APRS is good for, of course.
Depending on network coverage and load, it’s possible to communicate over a range of
hundreds of miles using the radio network alone. However, being a shared network, reliability
decreases with each added digipeater hop. APRS is most reliable at the local level, and it’s rarely
advisable to use more than two or three digipeater hops. Often, a single hop is adequate for
local coverage.
The APRS protocol, hardware, and software can be used independently of the national networks,
as well. Local or temporary networks may be set up to cover special events or to fill the needs of
a particular organization. Some uses may not require digipeaters at all – high altitude balloons,
for example, often use APRS to transmit position and telemetry data on a dedicated frequency
directly to the chase teams.
Mobile use of APRS can take a number of different forms. The simplest mobile APRS setup is a
transmit-only tracker connected to a radio and GPS receiver. These trackers generally have no
receive capability, other than to check that the channel is clear before transmitting. They allow
the vehicle to be tracked by others, but can’t receive messages or positions.
Another option is an APRS-capable radio, like those sold by Kenwood and Yaesu. These radios
have a text display, but require a mapping GPS receiver to display the positions of other stations
graphically.
An ordinary radio with a TNC can be used in conjunction with a laptop, tablet, or phone to
provide full APRS functionality, including mapping and messaging, although this is usually the
most expensive option and may not be practical to operate while driving.
