If it's not transmitting when he starts climbing it doesn't matter if he's carrying a detector or not. After he starts climbing, and then if the tower starts transmitting, what can he do about it ?

All a detector will do is let him know why he is falling to his death. Tell your buddy this can be a good example of how idiots are eliminated from the human gene pool.

Simple answer. Shut the power down which is related to the Antenna and then use the RF field detector to see if it is still transmitting or not.

Carry a RF field detector meter to test it !

Remember, a small 100W RF transmitter in any frequency is able to give a good electro-shock and throwing your buddy away and dead by falling down !

a small coil ( 100-200 turns ) connected to an led....when there is electromagnetic field ..it will light on ...

why he wants to climb ? say him ,it is vibrating on top parts...if he has not a safety-belt , he may fall .....

A small fluorescent tube or neon lamp, but your friend must have a death wish to do so.

Tune into the frequency or frequencies of its signal source or sources and monitor that.

My buddy wants to climb an antenna, but dosent want to climb it when it's transmitting. How can you tell if it's transmitting??