In the radio's init field:
this setPos [(getPos this select 0),(getPos this select 1),(getPos this select 2) + 2]
And change the 2 until it's at the right height.
What's happening here is that the getPos function is looking at the position of the radio (this) and splitting it into x,y,z coordinates in an array of output. So getPos radio select 2 returns the z value (height above ground, not sea level).