strong enough that it would overwhelm the radar's own signal, filling the radar display with noise and rendering the aircraft invisible. To test whether such a system would actually be effective, the RAF purchased a carcinotron from CSF and fit it to an aircraft christened "Catherine". In tests beginning in late 1954, the jammer proved to be able to render the area around the aircraft unreadable, even when the aircraft was still below the radar horizon. In one test, any aircraft to either side of the jammer was invisible, meaning a single powerful jammer could hide an entire formation of aircraft. As the jammer aircraft approached the radar station, the signal would be picked up in the radar antenna's side lobes, until the entire display was filled with noise and nothing could be tracked anywhere. It appeared that the decade-long effort to provide radar coverage for the UK was being rendered useless at a stroke. Plan Ahead As the nature of the threat of the carcinotron became clear, the Air Ministry began looking for potential solutions. Two concepts appeared to offer a potential solution. One was to simply overpower the carcinotron; although it could produce about a kilowatt of output in total, it would have to spread that signal across all the frequencies being used by the various radars. This meant the amount of energy in any one frequency was limited, estimated to be about 10 Watt per megahertz of bandwidth. If the receiver carefully filtered the return signal tightly around the broadcast frequency, it might only receive a few watts of jamming. With enough transmitted power, on the order of 10 MW, the signal reflected off a target at 200 miles would be about 11 W, thereby allowing the radar's signal to remain visible. This solution only worked if the carcinotron was forced to spread its signal over a wide bandwidth, and would not work if it could concentrate its signal into a smaller number of frequencies. To ensure this, the radar's signals had to be randomly spread across a wide bandwidth. This could not be accomplished with the magnetron, whose output frequency is a function of its physical construction, but this was possible using new high-power klystrons. This possibility was developed under the name "Blue Riband", using twelve klystrons that were randomly mixed together to produce an output signal on two widely separated frequencies. Another possibility was to