The onboard transmitter I use is 2.4 Ghz. It has 4 channels. That is you can switch between any of four frequencies. The only requirement as far as I know in Australia is the power output.
Have a look at
http://www.allthings.com.au/Catalogu...der%20menu.htm
Seems like 10mw is the max allowed in australia.
I have used 10mw TX and it is adequate, not brilliant.
I am still experimenting!!!
Regards