Help required in making a RF beacon

[samthunderbolt]

I need to make a RF based beacon system. Expected range of operation is around 10 mins. I should just be able to detect whether the beacon is active or not. What is the easiest possible of making such a system ?

 

[chuckey]

What frequency are you licensed to operate on? What range do you need. What sort of aerial array do you use?
Frank