GB973800A - Automatic frequency control systems - Google Patents

Abstract

973,800. Automatic frequency control systems. SPERRY RAND CORPORATION. Oct. 21, 1955, No. 30224/55. Addition to 854,635. Heading H3A. The invention relates to the radar A.F.C. system described in the parent Specification, and comprises a modification of the circuits which operate the relay connecting the controlchannel-signals to the slow-sweep-search-generator (and disconnect the control channel during undesired image signals). In this modification, the selector relay 59 has normally closed contacts but is held open by a triode 63 in the absence of suitable pulses from the discriminator network 19. As the search generator sweeps through the I.F., positive pulses from the video amplifier 51 (which in the prior Specification were applied to the relay-closing- circuit) are fed through diode 54 to amplifier 67 to trigger blocking-oscillator circuit 68 which applies positive pulses through a long-timeconstant R.C. network 70, to a triode 63 causing it to draw grid-current and block, as the discriminator output falls between points A and B, Fig. 2 (not shown), thereby releasing relay 59 to close contacts 58, 61. The " holding circuit " comprises negative pulses from the second output of the discriminator (as before) which are connected over contact 61 to triode 66 which inverts the pulses and applies them to the triggering amplifier 67. Negative pulses from the video-amplifier 51 due to the first output of the discriminator are blocked by diode 64.