Abstract: Pulse radar apparatus particularly for marine use has a dispersive antenna so that transmitted pulses sequentially of two or more different frequencies are radiated in different azimuthal directions. The antenna is continuously rotated and the receiver has separate channels for the different frequencies and display means correlating information received on different frequencies from the same azimuth thereby to reduce sea-clutter on the display.

Abstract: A pulse radar apparatus has video quantizing means for digitally encoding the received video signals at a first clock rate. The encoded video is fed into storage means, read out at a second clock rate, converted to analogue form and applied to a cathode ray tube to give a display, e.g. a P.P.I. display. The cathode ray tube has a constant time base speed and different range scales for the display are obtained by switching the speeds of writing into and/or reading out of the store. Multiple stores permit asynchronous reading and writing. Multi-level amplitude coding of the video amplitude is employed.

Abstract: A receiver for a pulse radar apparatus has a pulse length discriminator in which the amplitude of the received radar signals after detection is sampled at a rate such that there would be a plurality of samples, e.g. 4 to 12 samples in the time duration corresponding to the transmitted pulse length. Processing means are provided giving an output only when the number of successive samples having a predetermined amplitude lies between predetermined limits, e.g. not less than 4 and not greater than 8.