I will be glad to give you information regarding the balloon transmitter.It is a very simple circuit using a single 2n2222 transistor.As small as it is,the signal is very strong at high altitudes as mine was heard for over 5 hours after launch. I would love to try my hand at APRS…but the cost is out of my league.Here is a photo of the transmitter using a crystal from an old 56k modem (28.224) and a picaxe keyer circuit.Look me up on QRZ.com for my email if you want a schematic. http://s430.photobucket.com/user/N2NXZ/media/DSCF0038.jpg.html?sort=3&o=34
Jim,N2NXZ