Barrage jamming is radio jamming accomplished by transmitting a band of frequencies that is large with respect to the bandwidth of a single emitter. Barrage jamming may be accomplished by presetting multiple jammers on adjacent frequencies, by using a single wideband transmitter, or by using a transmitter capable of frequency sweep fast enough to appear radiating simultaneously over wide band (e.g. a carcinotron). Barrage jamming makes it possible to jam emitters on different frequencies simultaneously and reduces the need for operator assistance or complex control equipment. These advantages are gained at the expense of reduced jamming power at any given frequency. Barrage jamming has to be used against frequency-agile radars, which change frequencies too quickly to follow them in a conventional way. The use of barrage jamming may also affect the communications capability of the jamming source in a negative fashion.
Photomultiplier tubes were popularized during World War II since they could be used as high bandwidth (up to several hundred MHz) noise sources. Although wide bandwidth sources typically suffer from low spectral power per unit frequency, the photomultiplier tube offers high gain (about ) amplification of photon shot noise, making it advantageous over other lower gain noise sources.
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