[aprssig] Tactical Digi use

Wes johnston wes at kd4rdb.com
Mon Mar 20 16:50:46 CST 2006

We had to learn the hard way that when you work an event with aprs, you'd 
better setup your own digi's...  There was so much QRM rolling in from 
points afar that I couldn't track a bus with a 5w HT and mag mount antenna. 
The QRM is much reduced since we've implemented the new WIDEn-n system.... 
but the lesson has been learnt.  (is that even a word?? ;-) )  Now we have 
enough portable digi equipment to cover a fairly large area.  Recently it 
was a 5 x 20 mile area for a motorcycle race.  We managed to cover the 
heavily wooded and hilly area with 1 digi that we moved in the middle of the 
event and a d700 in a car.  The tracker was a 5wHT with a stubby duck 
antenna.  We used 144.99 - dead in the middle of the now largely quiet 
packet subband.

I think Bob makes a good point... setup your own digis on some different 
frequency, for example 144.99.  I wouldn't change any of the paths on the 
trackers.  I'd just run mobile digipeaters.  Another suggestion would be to 
have cross frequency trackers setup in the chase cars.  The chase cars just 
have to stay within 3 to 5 miles of the low power trackers.

Is the race BRAG? (bicycle race across GA?)

----- Original Message ----- 
From: "Robert Bruninga" <bruninga at usna.edu>
To: <kd4moj at kd4moj.org>; <aprssig at lists.tapr.org>
Sent: Monday, March 20, 2006 5:01 PM
Subject: Re: [aprssig] Tactical Digi use

>>> kd4moj at kd4moj.org 03/20/06 4:09 PM >>>
>...on a two day 200 mile biking event in April.
> I would like to switch the local digi's and route
> digi's (temp setups) over to a tactical type
>path so if the band opens up the trackers don't
>get clobbered over.

1) An ambitious undertaking.  Can you catually
get access to ALL digis in the entire area to
make the switch?

2) If you stay on 144.39 nothing can protect you
from RF QRM.  If you are going to adjust every
digi anyway, then why not move to 144.99 if
available in your area... and then hav ea clear channel.

3) Since we have receommended that all Kenwood
D700's be permanently set to support TEMPn-N
digipeating in the UITRACE parameter, you might
think of setting them up and the fixed digis to that
setting  at the same time for the event.

4) SOunds like your intent is to not support WIDEn-N
during the event.  A lot of locals may have problems
when normal tracking ceases.

5) Better thing to do might be to just make sure
ALL surroundign digis have good UIDIGI TRAP
aliases in place to trap expected QRM...
good luck

  Has anyone set up digi's to only respond to trackers for an event like
this? This event covers from N florida into S Georgia (Albany) and I
contemplated using the GA state path since there are not many S Georgia
digi's.  Any other ideas?


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