Thanks Calvin
Ham radio operators have a particular need for a transmitter shield that can work on 144-148 mhz (the 2m band). The reason is that we have a worldwide network of receiving stations that can receive digital positional information and then transmit it into a world wide map
see
http://aprs.fi (scroll to your nearest big city and look at all the things being tracked)
We also have a frequency in this band which is monitored by the International Space Station and can forward packets of data received by radio into the APRS network.
Putting that aside we have a amateur radio operator here in Melbourne VK3YT (Andy) who has been building small helium filled balloons with onboard transmitters. He recently had an onboard 434.500 mhz transmitter sending ssdv pictures and data.
This is probably the sort of transmitter he was using
http://www.robotshop.com/en/rf-link-transmitter-434-mhz.htmlIt puts out 25 mw of power which is hardly anything. But up in the sky with clear line fo sight, that signal can be heard for vast distances, especially with a well designed antenna. Andy used just 10mw and was heard by repeaters and gateways 100 kilometres away.
cheers Peter