Raids on illegal broadcasters have led to 44 pirate radio stations in London being taken off air.
The operation by communication watchdog Ofcom also uncovered drugs and weapons, including firearms.
The raids targeted studios broadcasting on the FM radio band used by the London Fire Brigade and National Air Traffic Services (Nats).
The problem is worst in London which has half of the UK's estimated 150 pirate radio stations.
In total, 53 transmitters were seized and Ofcom has also sent nine warning letters to nightclubs who had advertised on the illegal stations.
Robert Thelen-Bartholomew, Ofcom's Head of Field Operations, said: "Illegal broadcasting affects safety of life services and has links with serious crime.
"Ofcom will continue to pursue and prosecute those involved in this criminal activity."
John Anthony, London Fire Brigade assistant commissioner, said: "Pirate radio transmissions interfere with, and sometimes entirely disable, the communications systems the London Fire Brigade relies on.
"The interference makes it more difficult for the fire fighters to go about their daily business of protecting Londoners."
And a Nats spokesman said: "Unauthorised broadcasts on or close to frequencies used by air traffic controllers can interfere with the passing of vital information between air traffic controllers and pilots."
The raid which began on Saturday and ended on Wednesday night was a joint operation by Ofcom and the Metropolitan Police.