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oups.com...
Sirs:

I am a programmer and electrician, but not a radio person! I am
sending an experimental balloon to over 100,000 ft. I have purchased
two 900MHz RF Aerocomm ConnexLink Radios. The radios have a power of
1000 m.a., which states it will transmit and receive up to 20 miles
line of sight. I do realize that this is probably under ideal
circumstances and will not likely be the case when I actually deploy.
I would be interested in purchasing some antennas which would somehow
increase the range. What sort of characteristics make up a good
antenna for what I want to do? It is possible that someone could find
me one that would work with my project? Also, anything you might
contribute concerning radio transmission would be very much
appreciated.
Money is no object for this experiment, so any ideas you have are very
much welcome.

Just about any antenna will work . I would look into a 1/4 wave antenna
mounted upside down so it is pointed down for the balloon. I hope you ment
1,000 mw, or one watt of power for the transmitter. I have heard the hams
in the space shuttle and space station with a 5/8 wavelength on my car.
They only run a few watts and are over 100 miles up. Also talked with an
airplane at 40,000 feet that was over 150 miles away. I was using a 10 watt
radio and a small beam. He was using a handy talkey with maybe 5 watts
inside the plane. Unless you are under a bunch of trees , there is not
much beter conditions than to be line of sight. While it will probably be
too small to see without a telescope, as long as the balloon is in sight
almost anything will work.