[aprssig] > 1. Airborne APRS (William McKeehan)
K. Mark Caviezel
kmcaviezel at yahoo.com
Fri Oct 28 12:27:14 CDT 2005
I've tracked and recovered tons of balloons, mostly
from car, but also some from planes.
Firstly, by performing a flight prediction with
BallTrack or other balloon trajectory software, you
can have a good idea where the balloon is going. If
the prediction indictates it's gonna fly into a
badlands area, consider moving the launch site.
Having a ham near the predicted landing site,
receiving packets from the balloon is a great thing.
Observe wind speed and direction, and you can gin-up a
very useful dead reconned location from the last
balloon packet be it 500 ft AGL, 1000 feet AGL, or
whatever. With the dead reconned position, 'sniff'
the area with a 4 element beam and there is an ok
possibility that you can recieve a decodable packet
from a package on the ground. Sometimes I
ocassionally stop and hop up on the roof of my SUV and
hold the antenna at armlength over my head which gets
it a useful 11-12 feet off the ground.
Having a good topo map can be useful. If the dead
reconned position is 1/4 mile from the nearest road
(but with high terrain between), but shows a possible
view factor to a road 2 miles in the other direction,
drive and listen on the road 2 miles out. If you get
a good packet from the package on the ground, that
makes it all easy.
Ok all that said, from inside a plane, I'd suction cup
mount a D7 HT right in the window. Run it on
batteries to avoid cockpit clutter. Putting a real 2m
antenna on a plane is an expensive chore that most
aircraft owners and all FBO operators avoid like the
plauge. Because of the high noise level in any
general aviation cockpit, and the incompatibility of
the aviation muffs with your ham HTs, a good air to
ground voice link can be like this: use the aircraft
radio on an appropriate freq to talk to hams on the
ground (many ham radios can monitor, but not transmit,
the 118-136 MHz AM aviation band), and use 2m ham
freqs for ground to air. The pilot or passenger can
use an 'earbud' earpiece under his noise attenuating
muffs to monitor the ground-to-air voice comms.
- KMC ng0x Denver hot air balloon ng0x-11
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