Kenwood TH-D72A/E - Manual (Page 65)

7 APRS NETWORKS
TH-D72A/E CONTENTS 57
The greatest feature of APRS is the network that is spreading around the world. The heart of the
network is made up of many digital repeaters commonly referred to as digipeaters. Of course,
digipeaters are well-known among those who have used packet radio for years. Digipeaters receive
data over-the-air via radio signal and repeat or relay it onward. For a voice repeater, two different
frequencies are used simultaneously to accomplish this repeater function. However, a digipeater first
receives and stores data, and then transmits when the channel clears.
In the earlier times of packet radio and digipeaters, it was required to specify the callsign of each
digipeater station. But it was difficult to know which digipeater station to use. If moving in a vehicle,
you had to constantly consider changing digipeaters. Now, APRS uses a common generic callsign
for all digipeaters referred to as WIDEn-N, where N is the number of hops desired through the
network (typically 2 or less). The WIDE terminology lets you know the digipeater is in a good location
for repeating signals. A mobile station anywhere only has to specify WIDE1-1 without needing to
know a specific callsign of a digipeater in order to digipeat their beacon transmission.
APRS evolved over many years beginning in 1992, and there were many inefficient older network
concepts that were still being used in some areas. You still may see references to these obsolete
techniques (RELAY, WIDE, TRACE, and TRACEn-N). By 2004, it was decided it was time to
abandon those many older inefficient paths and concentrate on only the fully traceable WIDEn-N
algorithm. The APRS network was universally upgraded to just the one simple and traceable
WIDEn-N concept. This operating standard was called the New-N Paradigm. Since its adoption,
most areas have seen many improvements in local area APRS reliability. In most areas, the number
of hops should be no more than 2 hops. This was because additional hops just add too much
network load and too much interference from stations far away.
The following sections explain configuration of the TH-D72A/E for use with digipeaters.
With UIDIGI activated (On), when a digipeater receives a UI frame with a character string for alias
(such as RELAY, WIDE1-1, etc.) that matches the alias character string in the digipeater, the
digipeater repeats the packet substituting the callsign from the digipeater’s My Callsign configuration
and adding a completed flag ( ).
UIDIGI should normally be off. It is not good for mobiles to be digipeating all packets on the channel
because it causes much interference. But sometimes, in special cases, when a mobile is being used
on top of a hill or in a special weak area to provide temporary emergency digipeating, then UIDIGI
can be enabled with the WIDE1-1 alias so that this mobile can serve as the first hop out of an area.
In this case, the mobile station operates as the first hop of the first relay station for this area. WIDE1-
1 digipeating only operates on the first hop, so there is not much damage to the network or to other
traffic.
Figure 7-5 Using UIDIGI
7.4 Digipeaters (Digital Repeaters)
7.4.1 UIDIGI
My callsign: W6DJY-1
UIdigi: ON
Aliases: WIDE1-1
WB4APR-7 > APK103,
WIDE1-1, WIDE2-1: Test WB4APR-7 > APK103,
W6DJY-1*, WIDE2-1: Test