Spark Gap Switches for Radar

N ESSENTIAL feature of radar is the generation, by means of an "oscillator, of high-energy pulses of short duration, repeated many times a second. The energy for these pulses is furnished to the oscillator from a power supply in a variety of ways. One of the most widely used of these is the "line type modulator" in which a pulse-forming network made up of a series of condensers and inductances is charged from the power supply through a choke and is then discharged by a switch so that a substantially constant current will flow for a predetermined short time through the primary of a pulse transformer coupled to the oscillator. This switch is, therefore, an essential component of this type of modulator. To meet the pulsing requirements of radar as it developed during the war, this line modulator switch was required to withstand thousands of volts between pulses and to carry hundreds of amperes for the pulse duration which was of the order of microseconds. Also, the switching operation had