MANAGING A DIGI FOR LOCAL EVENTS                        19 April 2007
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                                                               WB4APR

Although the New-N Paradigm vastly improved the APRS network by
eliminating most of the duplicate packets and QRM, there are still
things that a Digipeater SYSOP can manage temporarily in real time 
to make his local digi more responsive to local events.

WIDE1-1,WIDE2-1:  The first thing to do even before any situation
arises, is to educate all local operators that the most effective
universal APRS path for mobiles is WIDE1-1,WIDE2-1.  Not only does
this give them the best general path, it also greatly simplifies the
job of the network manager since eveyrone is using a consistent path
and so he can make temporary network adjustments in case of any given
situation.

IGATES:  If the APRS-Internet link is important to your event, it is
very important that an IGate and backup be located as close as 
possible to the event.  Preferably able to hear every possible 
participant via the first hop from their locations.

LOCAL NETWORK MANAGEMENT:  Given that most APRS packets on the air
are using the traceable WIDE1-1,WIDE2-1 or WIDE2-2 paths, this allows
the network to separatly manage what it does with FIRST Hop packets
as distinguished from 2nd or more hop packets.  Since most packets at
an event are local direct, or one-hop packets, this distinction can
be used to great advantage to limit QRM and thereby improve network
reliability in the local area.

LOCAL EVENT DIGIS IN BIG SITUATIONS:  The following example is
derived from the recommendations for the annual convergence of many
thousands of hams and hundreds of APRS mobiles on Dayton Ohio.  
This usually results in more than 150 APRS mobiles in range of
one or two or more digis.  If these digis are operated normally,
the overall network will be exceptionally unreliable for any
individual since his packets will have unbelievable competition
to be heard.  What follows are the receommendations for such a large
event.

OBJECTIVE:  LIMIT THE AREA TO ONLY LOCAL APRS TRAFFIC:  This 
simple technique will eliminate all ROUTINE out of area packets 
from  entering the local situation.  Here are the steps:

- Record the existing DIGI settings so you can restore afterwards
- Set UITRACE TEMP,30  (is normally UITRACE WIDE,30)
- set UIDIGI ON WIDE1-1,WIDE2-2,WIDE3-3 (normally WIDE4-4,WIDE5-5,etc)
- Post an APRS Bulletin announcing the area as a 1 hop area.

These changes above will cause all conventional mobile and fixed
station paths in the area to all be digipeated ONCE and then no 
further propogaton occurs.  This assures that all mobiles and local
stations can be seen, yet does not require the participants to make 
any changes to their mobiles.

FOR OLD KPC-3's VERSION 8.2:  The above steps apply to a modern KPC-3+ 
v8.3 or later. The steps for an 8.2 ROM are diferent:

- Record the existing DIGI settings so you can restore afterwards
- Set UIFLOOD TEMP,30  (is normally UIFLOOD WIDE,30)
- Set UIDIGI ON WIDE1-1,WIDE2-2,WIDE3-3 (normally is WIDE1-1,WIDE4-4,etc)
- Post an APRS Bulletin announcing the area as a 1 hop area.

The difference is that version 8.2's already have WIDE1-1 in the 
UIDIGI list, but still need WIDE2-2 and WIDE3-3 added.  And in the
version 8.2 WIDEN-N is supported in the UIFLOOD paramter instead
of the UITRACE parameter.

Notice that the way we turn of WIDEn-N is to simply replace it 
with TEMPn-N.  THis way, the digi can still be used if needed as
a TEMPn-N digi.

EXPLAINATION:  The way this works, is that the UIDIGI ALIAS list
takes precedence.  So if the packet has WIDE2-2, and the digi has
that in its UIDIGI list, then it will digipeat, but do callsign
substitution.  So the WIDE2-2 becomes just DIGICALL* and that is
as far as the packet goes.  I included WIDE3-3 in the above 
lists incase some clueless individual arrives with his tracker
set that way.  It does no harm, becuse he like everyone else will
be limited to only one hop anyway.  If you dont expect to need 
this, you can leave out the WIDE3-3 from the UIDIGI list.

If most out-of-area QRM is coming in from only one direction
from a nearby city, then the above techniques may only need to
be applied to that one digi only.

MESSAGES INTO THE AREA:  Since you also assured that you have 
IGate's within one hop of the event digis, that assures that
all APRS messages from anywhere in the world can still get in
or out of the area.  And further any APRS person seeing the above
Bulletin in the area can work around these limitations as needed
by simply useing a directed path DIGI1,DIGI2 and get his packets
digipeated 2 hops any direction he wants.

Bob, Wb4APR