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[aprssig] > 1. Airborne APRS (William McKeehan)

William McKeehan mckeehan at mckeehan.homeip.net
Fri Oct 28 18:16:40 UTC 2005

The desire for an airborne tracker results from the first launch. They did not
get enough helium in the balloon and it nearly became a floater. It traveled a
long way and took hours to make the trip; missing the predicted landing zone
by miles (about 100 if I remember correctly). The only onboard APRS beacon was
a Pocket tracker on 144.39 - the number of packets received was very low, then
the GPS stoped working after a certain height was achieved. There were several
points along the chase that we thought we had lost it, then, out of nowhere,
somone would pickup a packet and the chase was on again. It made for a very
exciting (and long) chase! It also made them nervous about loosing their
payload. Should another flight give similar performance/problems, they were
thinking that an airplane flying over the area where they think it may have
landed would have a better chance of hearing the 250mw Pocket Tracker than
vehicles driving around it.

On Fri, October 28, 2005 1:27 pm, K. Mark Caviezel said:
> 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.
> good luck!
> - KMC ng0x Denver  hot air balloon ng0x-11

William McKeehan
Internet: mckeehan at mckeehan.homeip.net

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