GB639991A - Improvements relating to control apparatus for cathode ray tubes - Google Patents

Abstract

639,991. Radiolocation. DODDS, J. M., WHALLEY, H., and METROPOLITANVICKERS ELECTRICAL CO., Ltd. Jan. 3, 1947, No. 269. [Class 40 (vii)] Radar display apparatus for producing a rotating-radial or spiral time base comprises a cathode-ray tube CRT, Fig. 2, encircled by a symmetrical polyphase winding W having tapping points connected to corresponding points on a Selsyn-type transmitter T, the rotor of which is fed with alternating current and positioned in accordance with the aerial system. In order to produce a substantiallylinear time-base the tube beam is suppressed excepting over a portion of each alternating cycle when the current is either continuously increasing or decreasing. This is effected by the circuit comprising valves V1 and V2. The alternating wave A, Fig. 1, is applied to V1 and produces at the anode, a square wave which is then differentiated by C1, R1, the positive pips triggering a flip-flop circuit V2. A negative square-wave B generated at the left-hand anode is applied to the cathode-ray tube cathode and renders the time base visible over the linear portions ab, a<1>b<1>, &c. of the wave A. The positive square-wave D at the right-hand anode is differentiated by C5, R4 to produce wave E. The positive pips occur at the commencement of the time base and are employed to trigger the transmitter. Received signals at H modulate the tube grid. By operating the time base at twice the transmitter recurrence frequency, a spare display for calibration signals becomes available. The apparatus is suitable for producing plan-position and variable-elevation displays.