Converter Tube

a receiving tube that converts the frequency of electrical oscillations by mixing the oscillations with oscillations of another frequency; for example, in a superheterodyne receiver the signals received are mixed with oscillations from a local oscillator (see alsoFREQUENCY CHANGER and MIXER).

Converter tubes are usually multielectrode tubes, most often heptodes; combination tubes (triode-heptodes, triode-hexodes, and triode-pentodes) are also used. A typical feature is the presence of two control grids which permits dual control of the plate current in order to obtain combination oscillations. The mixer and the local oscillator are combined in a single envelope. If the local oscillator is a separate tube, the other tube is only used for mixing frequencies, in which case it is known as a mixer tube.