A Simple Logarithmic Receiver

A receiver with a logarithmic input-output law can be used with advantage on radar equipment, but it has hitherto been difficult to obtain such a law without the addition of a considerable number of tubes. One system by which such a law can be obtained is described and a circuit is given which shows how the method may be simplified to produce a receiver which can be either logarithmic or linear by the operation of a single switch. A method of predicting the shape of the input-output curve of such a receiver is described. The measured input-output curves for three logarithmic receivers of this simplified type are shown and the relevant circuit values specified. Some design notes are added. A note on the use of the logarithmic receiver as an anticlutter device is followed by consideration of the display of signals from a logarithmic receiver, and a brief discussion on bandwidth variations.