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7 APRS NETWORKS
TM-D710A/E CONTENTS 37
UIDIGI
UIDIGI: ON
ALIAS: SAR
(other local paths can be defined here)
Note: SAR stands for “Search and Rescue”.
UIFLOOD
UIFLOOD: ON
ALIAS: SS or SSS
SUBSTITUTION: ID
(where SS or SSS is the abbreviation of state or ARRL section)
UITRACE
UITRACE: ON
ALIAS: WIDE
7.4.5 Proper Configuration (written by Bob Bruninga, WB4APR)
New-N Paradigm recommends three major routing paths. The most important is the National
Standard of WIDEn-N (usually 2-2). It should always be used for routine operations. However
there are two other possible network arrangements for special situations: SSn-N and TEMPn-N.
SSn-N is for state or ARRL section communication special nets. These nets are called up for drills
or for emergencies. During these periods, it is desirable to have all APRS participants over the
state or section area to be able to communicate among each other. In some states, this may take
more than a 2-hop path. But using more than 2 hops also causes many packets to go outside of
the state and to add QRM in adjacent areas which is poor operating practice.
To allow longer hops within the state or section for these events, the SSn-N routing mechanism
can be used. For example, using WIDE3-3 from the middle of Maryland would reach all
digipeaters in Maryland, but someone in the far west or far southeast would need 5 hops. But
such a 5-hop path would cause QRM over 13 states! However, by using the state routing path of
MD5-5, the sender’s packets will go a full 5 hops in Maryland, but will not go into any adjoining
states. In fact, for the user in the center that only needs 3 hops, it does not make any difference to
use MD5-5 or MD3-3, because in either case, his packets will hit all the digipeaters in Maryland.
So for state-wide drills, the recommended path is MD5-5 for all participants anywhere in the state.
The TEMPn-N system is an emergency backup system that is inherent in all TM-D700A/E and
TM-D710A/E mobile transceivers. These transceivers can all be used as backup emergency
digipeaters in support of special needs. All mobiles should be programmed to act as digipeaters
for TEMPn-N packets. In this way, these mobiles are always ready and enabled to act as
digipeaters for this special path but, on the other hand, they do not digipeat any other packets so
they do not add any QRM to normal operations (using WIDEn-N or SSn-N). But at any time,
someone in a valley, or after digipeaters are lost in an emergency, the path of TEMPn-N might be
able to get out by hopping mobile to mobile.
To further benefit this alternate backup digipeating technique, some special battery-powered
backup digipeaters at high locations can also support this path.