Editing Cavity magnetron (section)

===Radar===
[[File:Magnetron radar assembly 1947.jpg|thumb|upright=1.4|9.375&nbsp;GHz 20&nbsp;kW (peak) magnetron assembly for an early commercial airport radar in 1947.  In addition to the magnetron (right), it contains a TR (transmit/receive) switch tube and the [[superheterodyne]] receiver front end, a 2K25 [[reflex klystron]] tube [[local oscillator]] and a 1N21 [[germanium diode]] mixer. The waveguide aperture (left) would be connected to a waveguide going to the antenna.]] 
{{Main|History of radar#Centimetric radar|l1=History of radar (Centimetric radar)}}

In a [[radar]] set, the magnetron's waveguide is connected to an [[antenna (electronics)|antenna]]. The magnetron is operated with very short pulses of applied voltage, resulting in a short pulse of high-power microwave energy being radiated. As in all primary radar systems, the radiation reflected from a target is analyzed to produce a radar map on a screen.

Several characteristics of the magnetron's output make radar use of the device somewhat problematic. The first of these factors is the magnetron's inherent instability in its transmitter frequency. This instability results not only in frequency shifts from one pulse to the next, but also a frequency shift within an individual transmitted pulse. The second factor is that the energy of the transmitted pulse is spread over a relatively wide frequency spectrum, which requires the receiver to have a correspondingly wide bandwidth. This wide bandwidth allows ambient electrical noise to be accepted into the receiver, thus obscuring somewhat the weak radar echoes, thereby reducing overall receiver [[signal-to-noise ratio]] and thus performance. The third factor, depending on application, is the radiation hazard caused by the use of high-power electromagnetic radiation. In some applications, for example, a [[marine radar]] mounted on a recreational vessel, a radar with a magnetron output of 2 to 4 kilowatts is often found mounted very near an area occupied by crew or passengers. In practical use these factors have been overcome, or merely accepted, and there are today thousands of magnetron aviation and marine radar units in service.  Recent advances in aviation weather-avoidance radar and in marine radar have successfully replaced the magnetron with [[Gunn diode|microwave semiconductor oscillators]], which have a narrower output frequency range.  These allow a narrower receiver bandwidth to be used, and the higher signal-to-noise ratio in turn allows a lower transmitter power, reducing exposure to EMR.