[aprssig] Cave Radio Paths

[Robert Bruninga]

Cave Radio Paths:



I think we have an idea on how to do all the PATHS so that the transition
between cave HOP7-7 to a WIDE2-2 above ground is possible.  The description
is  about 50% down my http://aprs.org/cave-link.html  page.  It uses the
TRAPPING capability of the UIDIGI Aliases to truncate HOPn-N paths from
going topside while continuing with the remaining WIDE2-2 topside.



The cavers use the path of HOP7-7,WIDE2-2.

The cave digi below a vertical link has the callsign of VERT.

The topside digi for that vertical link has the callsign of TOP



The TOP side digi has callsign-substitution (UIDIGI) aliases of
HOP7-3,7-2,7-1  so that it traps these and forwards only “TOP*,WIDE2-2”. It
also traps 7-7 so cavers wandering around topside can also make it without
changing paths.



The VERT digi in the cave has UIDIGI aliases of HOP7-7,7-6,7-5, 7-4 so that
it traps the others.  Its remaining path of VERT*,WIDE2-2 then gets
decremented at the TOP to VERT*,TOP*,WIDE2-1.  So as long as there is an
IGATE within one digi hop beyond the TOPside digi, then we have APRS-IS
communications independent of where the caver is out to CAVE7 without any
more QRM than 2 hops topside.



If we actually want to extend this to 14 hops in the cave, then those DX
cavers once they get beyond the CAVE6 digi can switch to H77,H77,W22. Here
is what  I think this longer path will look like topside for each case:



At VERT out to CAVE3:  VERT*,TOP*,W2-2   -  Works Topside

At CAVE4  & 5:  TOP*,H7-N,WIDE2-2            -  Fails topside due to unused
H7-N

At CAVE6 to 10:  HOP7*,VERT*,WIDE2-1   - works topside

At CAVE11 to 12:  HOP7*,TOP*,WIDE2-2   - works topside

At CAVE13 : HOP7*,HOP7*,WIDE2-1          - Works Topside

At CAVE14: HOP7*,HOP7*,WIDE2*             - Works if IGate can hear TOP
direct



SUMMARY:

PATH: 77,22 works from T, V, 1,2,3,4,5,6 with at least W2-1 to go

PATH: 77,77,22 works at  V,1,2,3,4, x,x,7,8,9,10,11,12,13,14



So for perfect coverage, cavers should only transition to 77,77,22 only
beyond 7.  But since they can see on a D72 what digi heard them, then they
can know when to change.



Anyone topside can reach any caver with the EXACT path to get to the TOP
digi plus H7-7,H7-7 remaining



We might be able to add an additional UIDIG trap in some  of the CAVEN
digis to solve the CAVE4 & 5 problem, but my head hurts to much to figure
it out right now..



Anyway, at least for 7 hops to the nearest VERtical digi, we have a working
plan for transitioning from below ground into the APRS-IS without any
additional topside QRM and without any caver changing paths.  And out to 14
if they will change..



Of course, using digis with PREMPTIVE digipeating solves all these problems.



So, planning is still proceeding for the 2-3 March Mammoth Cave Radio test.



Bob, Wb4APR
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