Sutton tube

For this reason, from late 1941 onward, it was replaced in many sets by the Western Electric 707A (also known as McNally tube, named by its developer).

The second use, sometimes known as a soft Sutton tube or rhumbatron switch, was a key component in the development of microwave radar by Britain during World War II.

Klystrons share the basic concept that the microwave output is generated by progressively accelerating then slowing electrons in an open space surrounded by a resonant cavity.

The first cavity is connected to a source signal, and is designed to resonate at the desired frequency, filling its interior with an oscillating electric field.

The cavity's dimensions are a function of the wavelength, most are flat cylinders the shape of a hockey puck of varying sizes.

As they pass, the bunches cause a varying electric field to be induced in the cavity, re-creating the original signal but at much higher current.

[2] The introduction of the cavity magnetron caused a revolution in radar design, generating large amounts of power from a compact and easy-to-build device.

Among these was a suitable local oscillator about 45 MHz different than the transmitter signal, which fed the intermediate frequency section of the receiver circuits.

[4] As the receiver circuit requires only very little output power, the klystron, first introduced only two years earlier, was a natural choice.

Sutton, a well-known expert in tube design, was asked if he could provide a version that could be tuned across the same range as the magnetron's drift.

By changing the voltage of the reflector relative to the gun, the speed of the electrons when they reached the cavity the second time could be adjusted, within limits.

[5] This modification effectively folded the klystron in half, with most of the "action" at the center of the tube where the input and output from the single cavity were located.

This advantage was offset by the lack of a switching system to allow a single antenna to act as both a transmitter and receiver.

This is not always a major problem; the Chain Home system made do with two sets of antennas, as did early airborne radars like the Mk.

This was filled with a dilute gas, initially helium or hydrogen,[10] but eventually settling on a tiny amount of water vapour and argon.