If your friend is flying with an FPV-setup he should be aware of the allowed frequencies and transmitting-power.
In most european countries only 2.4 and 5.8 GHz are usable, also with limited TX-power.
2.4 Ghz -> 2.400 - 2.500 GHz (limited to 10mW)
5.8 Ghz -> 5.725 - 5.875 GHz (limited to 25mW)