Owen Duffy wrote in
:

On Fri, 28 Jul 2006 21:20:43 GMT, "Ralph Mowery"
wrote:


wrote in message
groups.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

So that would have its pattern null pointed down at the earth?

Not to imply that the balloon would necessarily be directly above the
observer(s), but if and when it was at the zenith, it would be
relatively hard to hear.

I used to do a lot of radiosonde work. Those balloons would go to
110,000 feet at times. The transmitters were small, probably not more
than a watt, but we tracked them with an automatic system. The instrument
used a 1680mhz transmitter with an upside-down ground plane antenna in
the bottom (I think that was the freq. but it was near there). The
tracking antenna, though, was a parabolic dish with a wobbling feed-point
antenna that automatically tracked the balloon's radio, giving us a
continual readout of azimuth and elevation angles. By combining this
data with the received data from the instrument's aneroid barometer,
temperature and humidity sensors, we could locate the balloon with good
accuracy in three dimensions. Thus the run would provide temperature and
humidity profiles as well as data on winds aloft. Balloons almost never
go straight over you and when they do it is almost always early in the
flight when the signal is close and strong.

The OP hasn't told us the elevation angles of the locations of the
balloon in flight, how fast it is likely to spin, data rate or
equivalent (eg is this intended to send images back?), etc... they are
all relevant to commenting on suitability of the 1000mA??? radio, and
the type of antennas for the balloon and ground station(s).

A lot depends on frequency, too. Tracking a 2.4 or 5.8 ghz transmitter
is different from tracking a 35mhz transmitter.



--
Dave Oldridge+
ICQ 1800667