At an altitude of 100,000 feet 1000 mw [1 watt] should reach to the radio
horizon of about 300 miles assuming a good receiver on the far end of the range.

A vertically polarized 1/2 wavelength antenna should work fine. At least it
would be my starting point. Second option would be an inverted [upside down] 1/4
wavelength ground plane. Either antenna is not expensive.

What information is to be transmitted? If you are looking for moderate speed
telemetry then a path loss versus error rate study needs to be done. If data is
being transmitted a gain antenna may be required at the receiver. Gain antennas
are not expensive and the antenna needs to be pointed at and follow the
balloon's flight path.

/s/ DD

wrote:

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.

Thanks,
Brett