GB601733A - Improvements in or relating to object-locating or -detecting systems - Google Patents

Abstract

601,733. Radiolocation saw-tooth generating circuits. WATSON, D. S., LAWS, C. A., and BUCKINGHAM, J. June 8, 1945, No. 14635. [Classes 40 (vi) and 40 (vii)] A cathode-ray tube radar indicator with a type A scan is provided with means for increasing the speed of a small section of the time-base, a calibration mark generator, and gating.means for allowing only the calibration mark occurring in the expanded part of the sweep to provide an indication on the tube. Synchronizing pulses from the radar transmitter are applied over condenser C1 to amplifier V1 and the output applied to single-stroke multivibrator V2. A positive pulse from anode '' a " of this valve is fed to the suppressor grid of V4, which is an anode-grid coupled time-base generator, and the time-base sweep is applied to the X1 plate of the cathode-ray tube and also to the grid of " b '' section of cathode coupled double triode V6. The potential of the grid of the '' a " section of this valve is controlled by coarse ranging potentiometer P and when the sweep potential applied to the " b '' grid falls through the " a " grid potential, the current through the valve changes over from the '' b " to the " a " section and a negative pulse is passed to the grid of V7. This pulse is delayed after the start of the time-base by an amount determined by the setting of P and initiates the expanded sweep. V7 is normally conducting, but is driven to cut-off by the applied negative pulse, the anode potential rises as the anode-earth capacity charges up through R9, providing the fast sweep which is applied to the X2 plate of the tube. The negative pulse from V6 is also fed through a network providing a delay of half the duration of the expanded section of the time-base to V9 which passes a positive pulse to gate valve V19 at the centre of expanded time-base. The calibration marker generator is triggered by a negative pulse derived from the b section anode of V2; this is used to suddenly cut off valve V10 and cause ringing circuit L3 and C14-16 to oscillate. Oscillations are applied to cathode follower stage V11 and then applied to V12 which feeds signals back to coil L4 to maintain oscillation. In order that oscillation shall not be continuous, V12 is normally cut off by suppressor grid bias, but is allowed to function by a positive pulse applied from the " a " section of V2 at the same time as V10 is cut off. The feed-back resistor R15 is adjusted to maintain oscillation. V11 also feeds a second cathode follower V13 which is' transformer coupled to phase-shifting networks which feed in quadrature the two field coils F1 and F2 of a goniometer. The phase of the output of the search coil is dependent on the coil's position and this provides the vernier range control which may be linked with the coarse control. The search coil output.is fed to amplifier V14, to squaring and amplifying valve V15, and then to V17 which produces short positive calibration pulses from the squared wave. These are applied to the grid of gate valve V19, but only the one occurring near the centre of the expanded section of the time-base is allowed, by the positive pulse from V9, to pass on to provide either light or dark spot modulation of the trace. Specification 583,475 is referred to.