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[aprssig] Road Trip - Lessons Learned

Joel Maslak jmaslak-aprs at antelope.net
Sun Mar 18 03:17:24 UTC 2007


I tried a small caravan with another family member this weekend.  I  
decided to use APRS to track the other vehicle (I have a dash-mounted  
GPS unit hooked up to the D700, so I was planning on using it to  
track the other vehicle).

The tracker was a Garmin eTrex (yellow one) hooked to a D7 with an  
external antenna (1/4 wave magmount).


Lessons learned:

Portability of the tracker is nice, but not nearly as important as  
robustness and difficulty for accidental reconfigurations.  I might  
go to a business class radio next time, with only one channel  
programmed into it.  Early in the trip, I realized I wasn't seeing  
the other vehicle, so we stopped and took a look.  I was off- 
frequency, as a control got bumped.  I fixed that and the trip went  
pretty well.

Taking off-the-shelf batteries (AAs) in the radio and the GPS was  
very handy.  They work.  Rechargables should work but often don't  
(probably because I can just buy AA batteries while I have to care  
for and charge rechargables).

Ready made cables were a big plus.  Yes, I could solder the  
connectors together.  But not having to do that meant I had a cable  
that I actually trusted to stay connected.

I did 1 minute beacons for the "dumb" vehicle.  I am not sorry about  
that at all.  Even one minute at 70 MPH is quite some distance.   
Smart beaconing would be better.  Too bad my GPS+D700 doesn't do dead  
reckoning.  I figured back east we are out of an area's coverage  
relatively quickly, minimizing QRM.  Obviously I shut things off when  
stationary for more than a few minutes.

I used a path of WIDE1-1.  I also set the mobile D700 (50 W vs 2.5  
W!) to digi WIDE1-1 (yes, I know, bad practice in general), to let  
the packets from the dumb tracker get a bit further in the boondocks  
(most of the trip had no local digi coverage even with a 50 W  
mobile).  I might do WIDE1-1,WIDE2-1 next time to let it reach into  
the internet easier (I can pull up findu via my cell phone, so if we  
got seperated, couldn't hear a common digi, but the other tracker was  
within range of some digis, it'd be good to make it into the inet).   
This was handy because at one point we were separated by about 8  
miles, outside of simplex range, but a local digi was hearing the  
dumb tracker and my vehicle heard that fine.  I was able to meet up  
with the dumb tracker reasonably easy even with both of us moving  
down an interstate.  It was nice for one party to be able to do a  
quick stop without fear of being separated.  We had cell phones as  
backup, but we didn't need them.

We also used FRS between the vehicles.  That didn't work nearly as  
well - after more than 1/4 mile or so at the most, we lost  
communication that way.

One of the neatest examples was when we arrived at our destination  
and needed to find a hotel.  The other car was separated from me (I  
took a wrong turn).  I was able to still use FRS to talk to them, but  
their directions made no sense to me.  But I saw them on my GPS and  
drove right to the hotel parking lot that they were in.

This was hardly a life-and-death situation, and we would do fine  
without having APRS, but it was a nice thing to play with.




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