[aprssig] TEMPn-N and callsign digipeating

[Robert Bruninga]

At the expense of confusing everyone for Field Day which
plans to use TEMPn-N digipeating on 145.01, I am really
excited about how we can permanently use TEMPn-N 
for special situations on 144.99 along with the low-power
devices.  This is the ultimate arrangement AFTER field day:

1)  We begin building digis for low-power users with simple
144.99 ==> 144.39 digis using the alias of WIDE1-1 only.
ANY TNC can do this.  This is the alternate input channel
for low power APRS that has been previously published.

Very high digis on mountains that hear too much are ideal
for conversion to 144.99 alt-input digis, since they can
hear the low-power trackers over a very large area with
no QRM.

2) We ADD TEMPn-N support to these digis.  

3) Remember that D700 mobiles should always be configured
to act as TEMPn-N digis too for emergency operations.

With #2, and #3 above, then we can instantly provide
an alternate channel for reali-time APRS support by simply
asking D700's in key areas to park on a hill and set their
radios to 144.99.  They then act as hop-by-hop links
into an out of affected areas, but the permanent
ALT-INPUT-CROSS-CHANNEL digis provide the cross link
back to 144.39.

THis way, there is no digi-to-digi traffic on 144.99 and 
even the big alt-input digis do not contribute a single
bit of QRM to that "input" channel, but the D700
TEMPn-N digis can serve as range extenders into that
system!  Wow.

We can use this FD as a TEST of this concept!  It will
be on 145.01 this year since we have already published
that frequency, but it can then become permanent
on 144.99.

Imagine a single mountain top digi in California that can
hear tens of thousands of square miles, listening on
144.99 and the ONLY thing there are low power trackers.
The QRM level would be 0.01 what it is now on 144.39.
Remember this digi does not digipeat on 144.99, but
does cross digipeat to 144.39.  Thus it does NOT add
to any QRM that would reduce the reliability of the
trackers.  Yet, everyone on 144.39 could hear them.

And if this digi also supported TEMPn-N, then a mobile
parked on a hill even a hundred miles away, could
easily serve as an emergency link back to 144.39
by a simple twist of the frequency knob...

Hummh...   I'll write up a plan.
think about any really big digis that hear too much.
Maybe they are ideal for this application...

Bob, WB4APR



>>> bruninga at usna.edu 05/28/06 6:32 PM >>>
Yes, to transition to and from TEMPn-N, then
actual calls would be needed or other generics.

But if a TEMPn-N packet arrives at your location
as DIGI1,DIGI2,TEMP3-1, then it went through
two TEMPn-N diigs to get to you, so any TEMPn-N
response would get back to him.  But if the sender
sent the packet via  RELAY,TEMP3-3, AND there
was a RELAY digi on that frequency then
it would arrive as DIGI1,DIGI2,TEMP3-2
and you would have to have a quick eye to notice
that DIGI1 cannot be a TEMPn-N digi, because 
only 1 n-N hop was used (3-2).

BUT!!! Under this emergency operations scenario,
a REPLYING staiton could always use the return
path with explicit calls and it would have to always
work.  Maybe we have to come up with procedures
to eliminate these kinds of problems:  Rules:

1)  TO be CERTAIN of successful reply to an incomming
TEMPn-N messsage, try listing each digi explicitly.

2) Hum,m,h... we cannot tell senders to avoid
creative mixing of TEMPn-N and explicit digis, becuause
that is what this is all about.  Creating paths as needed
in special circumstances.  Therefore, I guess the
rule of thumb is to always reply with explicit list of 
digis unless one is smart enough to actually figure out
how the packet got to you in the first place.  ANd
some arriving paths will simply be ambiguous to be
sure...

So only rule is #1?

Bob

>>> wa7nwp at jnos.org 05/28/06 6:13 PM >>>
>>>> wa7nwp at jnos.org 05/28/06 12:54 PM >>>
>>... getting some TEMPn-N activity here for Field Day.
>>...   Does a TEMPn-N D700 mobile digi automatically
>>digipeat on the stations callsign or will it be necessary
>>to add it to the UIDIGI settings?
>
> Im not sure I follow, but TEMPn-N packets should work
> just exactly like WIDEn-N packets, but of course will
> only go through other TEMPn-N digis.


Once we learn (thanks to callsign substitution) the digi's to use to get
to a desired alternate station, we want to switch from using the generic
Tn-N to specific calls.  For example, once I learn that the path to the
WB4APR-13 airmail station is via the WA7NWP-7 TEMPn-N digi, I would switch
to using WA7NWP-7 to Connect to WB4APR-13.  The question is, does WA7NWP-7
have to be added to one of the four UIDIGI settings on the D700 or will
the D700 automatically digipeat on mycall.  (Yes I know - it'll take about
2 minutes to test it here.  Which I will do after the shortly upcoming
afternoon adventure..)

Bill


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