[aprssig] Balloon tracking questions

[Jason KG4WSV]

On Fri, Feb 25, 2011 at 1:44 PM, Ted11 <tedlists at hullar.com> wrote:

> 1.  Is there a dedicated balloon tracking list I should be sending my
> questions to?

Try the balloonatics yahoo group.

> 2.  Any recommendations for GPS, radio, and tracker combinations?

My current favorite is the T2-301.  We have also used the Alinco
DJ-C7, Yaesu VX-150, and basic Kenwood and Icom 2m HTs, all with
various versions of the OpenTracker. All work well.

Whatever you do, do NOT configure your tracker to wait for a clear
channel before transmitting - at altitude, the channel is _never_
clear.  I have left the RX audio wire disconnected (or cut it) on a
TX-only tracker, but I usually set the radio to RX on a different
frequency. 144.99 is easy, since it's 600kHz from 144.39.

> 3.  What is the best approach for power?

Lithium primary cells, e.g. energizer lithium AA, which is our
standard.  I've also flown several CR123A packs, and our students have
used some of the 3.6V AA lithium primary cells.

> 4.  What do you recommend for antennas, both on the balloon and on the
> ground?

I'll assume you're using 2m, like most folks.

For flight hardware, nothing has worked better than a dipole
tape-measure antenna, with the feed point inside the package.  A
simple wire dipole on a support (e.g. 1/4" wooden dowel) works well.
We have also used roll-up J-poles hanging below the balloon (taped to
the payload train).

Problems can occur routing the coax outside the payload.  We've had
failures due to cheap coax (PVC insulation) failing in the cold.
Using extreme temperature coax (e.g. mil-spec teflon) helps a lot, but
keeping the coax entirely inside the payload works very well.  Less to
snag on recovery, too, if your LZ has trees.

I've seen WB8ELK use the 1/4 wave HT antennas - they work well, too.
Point it down, since a 1/4 wave without a ground plane has a lobe off
the end of the antenna.

For chase vehicles, whatever you've got on your mobile.  The only
issue I've ever experienced is when the balloon was directly overhead
in the null of my Comet SBB-7.  The antennas we keep for student chase
vehicles are either Diamond 770 half-waves or 1/4 wave mag-mounts.
All work well.

VHF is line of site; if the balloon is in the air it's easy to hear.

Once it's on the ground, a yagi (e.g. Arrow, PVC pipe/tape measure
yagi, etc) may be useful.  You don't need it every flight, but when
you do need it, you need it bad.  One one occasion we had an antenna
failure (PVC coax) and the "antenna" was a 1" stub on the end of the
coax.  The arrow yagi pulled in enough signal to get a position report
and recover the payload.  On our last flight, the payload landed in a
lake; a tape measure/PVC pipe yagi got enough signal to get a position
report, and a fisherman took a team member our to recover it.

> wonder if there is a better approach to match
> balloon and receiver antennas.

That sounds extreme.

-Jason
kg4wsv