Nige, your right in #13, no competition there, some organizations though demand stuff like that.
Fankllll, a jammer doesnt generally remove or delete radio waves, it interferes with them, ie if you transmit audio tones on the same frequency as a radio station, and the person you target receives a higher signal from you than the radio station pretty much all they get is the audio tones.
Another more modern way is to use up all the channels on a microwave band, disabling devices.