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TH-D72A/E CONTENTS 53
7 APRS NETWORKS
In the beginning, APRS networks consisted only of general packet transmissions through digital
repeaters. To expand network coverage much further, HF gateway stations that were interfaced with
the VHF stations were added. This arrangement evolved still further when it became common for
personal computers to be connected with the Internet. Internet gateways provided another way to
expand APRS coverage. APRServe, developed by Mr. Steve Dimse, K4HG, allows information that
is gathered from the Internet to be transferred to client computers. The worldwide APRS network
was completed. The service is called APRS-IS (APRS-Internet Service).
At present, there are several basic servers that are called Core servers, under which a number of
local servers, called Tier 2 servers, work and are located worldwide in each participating country.
Later, Pete Loveall, AE5PL developed javAPRSSrvr to establish a Tier-2 distribution system to better
handle regional APRS-IS feeds. The Internet part of the APRS system is called APRS-IS (APRS-
Internet Service).
There are basically two ways to use APRS-IS effectively when operating APRS: a client personal
computer connected directly to Core/ Tier 2 servers, and using amateur radio with IGate (Internet
gateway).
For client use, a callsign is required, but amateur radio equipment is not necessary. You simply
install APRS software such as UI-View32 and AGWTracker on a personal computer, configure the
necessary station information and connect to an APRS server via the Internet. With this
arrangement, you can enjoy the basic features of APRS such as transmitting your own station
position, exchanging messages and dispatch or receipt of weather information.
Using TH-D72A/E, you can transmit your own packet signals via amateur radio and use APRS-IS to
access IGate. IGate acts as a two-way interface between the Internet and amateur radio packet
signals. The IGate function is obtained through various releases of APRS software and IGate is
commonly available as a result of many volunteer amateur radio operators.
IGate connects directly to Core servers and Tier 2 servers and information received by amateur radio
packet transmissions is transferred to the servers, and server information can be passed via packet
radio transmissions back to amateur radio operators.
Setting up an additional IGate station in an area that already has an existing IGate station will result
in providing the same information to the server and put an excessive load on the Internet, and
therefore is undesirable. Traffic from IGate to amateur radio stations increases air traffic; therefore,
you must be familiar with operational configurations.
Various filtering functions exist so you should be knowledgeable about your local existing IGate
station. In the case of packet messaging, bidirectional data transfers are used.
While operating TH-D72A/E from a fixed station, specifying a particular digipeater and the callsign as
the packet path to a nearby IGate station will guarantee packets will always be relayed by the same
path and can avoid unnecessary relays and therefore raise efficiency. In the case of a mobile station,
since the packet path changes from time to time, use the default packet path or follow local rules of
each area where you may operate.
7.1 APRS Servers
7.2 IGate