[aprssig] Road Trip - Lessons Learned
jmaslak-aprs at antelope.net
Sat Mar 17 22:17:24 CDT 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).
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
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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