I'm starting a new personal project in High Altitute Ballooning and would like to share it here in 
case anyone has some experience/interest to share in this fasinating hobby. My goal is to launch a 
small helium-filled weather balloon carrying a small payload of a few instruments consisting mainly 
of a camera, a few sensors and tracking electronics to successfully retreive the equipment. The 
balloon will ascent at a rate of 3-5 m/s untill it reaches its bursting point at an altitude of 
29-34 km, when the payload will fall back to earth. A parachute is attached underneath the balloon 
to provide a fairly save descent rate of 5-8 m/s for the payload. The payload may land hundreds of 
kilometers away from the launch point (depending on the wind at various levels), and after finding 
it, hopefully contains some interesting data and video/photos from the earth at almost a third of 
the distance to space. 

The tracking of the balloon is the hardest part, and I plan to use the following: a GPS receiver, 
RF transmitter, microcontroller and a GSM cellphone module. The GPS will send its coordinates to 
the micro, which parses it together with other sensor data for the RF TX. The GSM module also sends 
the coordinates with GPRS to a server or with SMS to a user. On the ground I have a radio tuned in 
to receive the data and to display it on a PC to track the balloon and to predict where it will 
land. 

I have done most of the work on the GSM side, but just starting with the RF. I have a AOR AR8200 
radio receiver and hope that I can use it. I will post more detailed information here or on my sdf 
website like what types of equipment I will use and antenna designs chosen etc. Theres a few very 
usefull articles for beginners from the guys at UKHAS on their wiki site, http://ukhas.org.uk/