Patent GB-758727-A (GB)
Title: Arrangement in constructions for automatic radio direction finding
IPC: G01S13/02
Filed: 1953-09-21
Abstract: 758,727. Radio direction-finding; radar. SVENSKA AKTIEBOLAGET GASACCUMULATOR. Sept. 21, 1953 [Oct. 6, 1952; Oct. 27, 1952], No. 25968/53. Class 40 (7). An automatic radio direction finder and a radar are arranged to scan the same field and to provide indications on a common indicator. The aerial systems 10 and 11 of the directionfinder and the radar respectively are arranged to rotate synchronously with each other and in fixed angular relationship. This may be achieved by mounting both aerials on the same vertical shaft driven by the same motor 11. By means of gearing 16 and 17 and mechanical linkage 18, 19, the deflection coil system of the cathode-ray tube indicator may be driven in synchronism with the aerial rotation. Signals picked up by direction-finding aerial 10 are fed through receiver and amplifier 141 to give an output pulse having a width dependent on the aerial beam. This pulse is fed over line 29 to timing device 42. Device 42 may be a device of the kind described in the Specification 740,362 which effectively determines the midpoint of the pulse fed to it and give a delayed short output pulse a fixed time thereafter. The short output pulse may be fed over slip-rings directly to deflection coil 21 of the indicator (Fig. 1, not shown) to produce a single radial line indication or over the additional circuitry shown. In this the output pulse from unit 42 is differentiated by elements 33 and 34, then fed to trigger monostable multivibrator 39. The square wave output 36 from this is differentiated at 40 to give two oppositely directed short pulses (37) which by means of transformer and rectifier network 41, 44 give two positive pulses 38, separated by a short period of time equivalent to the return period of the multivibrator, across the load 45. These pulses may then be applied over the slip-rings to coil 21 to produce two radial lines spaced angularly by a small amount. The radar apparatus 14<SP>11</SP> is connected to its aerial 11 by means of the lower pair of slip - rings. Its output fed over line 22 gives a correctly orientated P.P.I. on the indicator tube. The angular displacement between the direc. tions 31 and 32 from which the aerial systems are capable of receiving signals is arranged to exactly compensate for the delay introduced in unit 42 so that, in the case of the single linebearing indication, the bearing line on the display passes through the radar image of the object, giving rise to it. Where two bearing lines are displayed the radar image of the object is arranged to appear on the line bisecting the angle between the bearing lines. As the brightened bearing indication does not in this case pass through the radar image of the object the image becomes easier to view. The true bearing can readily be determined by taking the mean of the angles indicated by the two bearing lines on the bearing scale round the tube. In either arrangement at the same time as a bearing indicating pulse is fed from unit 42 a brightening pulse may be fed to the radar receiver amplifier to increase the amplification and thus the intensity of the radar image of the corresponding object.