[aprssig] TEMPn-N and callsign digipeating
Robert Bruninga
bruninga at usna.edu
Mon May 29 09:54:31 EDT 2006
>>>> "Wes johnston" <wes at kd4rdb.com> 05/28/06 9:33 PM >>>
>.. and the thing I can't grasp is _why_ change the
>alias to TEMPn-n? During an emergency, the
>last thing I want to be doing is reconfiguring a bunch
>of trackers.
Think of the backup TEMPn-N network only as a D700
capability only. That is all that TEMPn-N is, is the
ability to -pre-configure- all D700's as TEMPn-N
digis. This way, they are already configured and can
be called into service at any time or used by anyone
at anytime without having to use a laptop to
reconfigure each D700 each time it is needed.
So given that TEMPn-N is a backup D700 capability
only, this new idea of adding TEMPn-N support
to alt-input dgis on 144.99 too is just a way to then give the
D700 emergency backup system, a pre-configured
entry point back into 144.39.
> Much easier to just... make the only configuration
>change to the trackers to change the offset from simplex
>to +600.
That is all they ever have to do. Because the alt-input
system listens for W1-1 and in addition, any TEMPn-N
D700 tepmorary digis also listen for W1-1 (set from the
front panel).
But the key here, is that the purpose of temporary as-
needed TEMPn-N is to support emergency needs such
as messages into and out of an emergency area. It is
not intended to support trackers because the whole idea
here is to use TEMPn-N by stations that do not have to
be reconfigured with a PC.
Scenario is this. Emergency happens. WIDEn-N does not
work in an area at the scene. D700 volunteers to drive
to hill top. Instantly anyone in the area can get out
by changing their path to TEMPn-N because the D700
should already be configured as a TEMPn-N digi. All
of this is still on 144.39. Primarily for messaging in
and out of the deadzone area.
But this new idea is to simply
suggest that alt-input digis also be listening for
TEMPn-N packets. This is so that the D700's that
are serving as a backbone multi-hop link into or out of a
special area, can operate on 144.99 to drastically
eliminate the QRM and so that their traffic will move
much faster. Yet, this TEMPn-N traffic can be gated
over to 144.39 by any alt-input digi if needed.
>the thing that is paramount here is to make sure that
>only trackers TX on 144.99... all routed/digipeated
>traffic must stay on 144.39 so the trackers have nothing
>but other trackers to compete with.
Yes, but now I am suggesting that this channel can also
be used for emergency communications needs and the
range further extended using TEMPn-N. Again, not
for extending tracker range, (unless they can reconfigure)
but for extenindg messaging capability.
>My suggestion for high digi's that want to be alt input is
>that they go ahead and invest in a set of 2m cavities
>tuned 144.39/99. That way the digi won't go deaf on 99
>when it transmits on 39.
This is economically not justifyable. The TX dutycycle
of the alt-input digi is so low, that it makes no sense to
install cavities for such a low percentage of time that it
would make any difference. Say you have 5 low power
trackers at 2 minute rates in range of this digi. That
means that the probabilty of a collision you describe is
less than 5%. A really big Investment in cavities to
improve performance from 95% collision free to 100%
collision free is not a good return on investment.
>Also, holdoff sensing on 144.39 is very desireable.
Agreed.
Thanks
Bob, Wb4APR
----- Original Message -----
From: "Robert Bruninga" <bruninga at usna.edu>
To: <wa7nwp at jnos.org>; <aprssig at lists.tapr.org>
Sent: Sunday, May 28, 2006 7:15 PM
Subject: Re: [aprssig] TEMPn-N and callsign digipeating
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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