[aprssig] KPC3+ Question

[Robert Bruninga]

> A question for all KPC3+ experts out there.

Jim, I'm going to answer based on the lowest common denominator
of interpretation of the information you have provided.  That
is, I am assuming you have not implemented the New-N paradigm
settings on these digis.  Forgive me if you already have...  My
answers are more for others who may be following this thread.

> I have a scenario with eight KPC3+ digi's in 
> a mountainous area, which are set up to get 
> location beacons back to a central point.

Probably you mean they are "set up" situationally located for RF
such that they can all see the central point, that is one thing.
Again, I will assume a worst case assumption and assume you may
be talking about "TNC settings"...  In that case, there is
practically nothing you can do in a digipeater to "force" any
particular packets anywhere.  Where the packets go is up to the
originator of the packet.  If it takes 3 hops from one of those
digis to get the data back to the single specific point, then
users in that area will have to use WIDE3-3.

> Digi's are hill-top, so I want to stop beacons from 
> being repeated in areas they don't need to be (i.e. 
> cut down the redundant RF traffic).

Simply implementing the New-N Paradigm in the KPC-3+'s should
cut down on all dupes perfectly.  It eliminates all duplicate
packets.  Each New-N digipeater repeats each packet once and
only once.

> Control of the route via the sending station is not 
> possible as they can be anywhere, which is why I'm 
> looking for a "system" solution.  KPCs are running v9.1.

The system solution is to determine what the worst case path is
(say 3 hops) and have everyone in the area use three hops.  This
is easy to convey to users, since all DIGIS under the New-N
paradigm are supposed to show as the first few bytes of their
Position Comment something like "W3,SSn-N" to tell users that
WIDE3-3 is recommended in that area (and SSn-N is supported).
This displays nicely from all New-N digis.

Maybe you only want packets to go to the central site, but
focusing too much on that one-way path will exclude users in
your "system" from seeing each other at the extremes.  In my
opinion, you want packets originated anywhere in the area to be
able to hit all other digis, so that all users in your system
see each other too.  APRS is for all-to-all communications.
Most mobiles receive and display data as well as just transmit
it.

On the other hand, 

If your "system" is well defined and truly has a specific well
defined and well understood mission, then you can set it up with
a specific SSn-N system (SS can be from 2 to 5 bytes long).
Then tell all users in the system to use SSn-N where N is the
maximum worst case path from the fartherest extremes of the
system.  This will guarantee that all 8 of your digis repeat
each packet, but that NONE of the sourrounding states or areas
will see any of them.  This might be unfair for the overall
regional APRS communicatinos, but it will accomplish what you
say you want.  You can even use SS7-7 without regret, because no
matter how big "7" is, these packets will still only hit each of
your eight SSn-N digis once and only once.  And not spread
outward beyond your "system".

The KCPC3+'s all support both WIDEn-N and SSn-N simultaneously,
so this way you can meet your specific unique objective for
specific users while also serving the general APRS mobile public
as well.

Hope this helps.

By the way, if you do implemente the SSn-N system, then the
paths are the most traceable if the users use the path of
SS1-1,SSn-N.  This will identify the packets when they arrive
anywhere by the FIRST and LAST digis in the path.

Bob, WB4APR