GB528861A - Ultra-short wave course beacons - Google Patents

Abstract

528,861. Directive wireless systems. STANDARD TELEPHONES & CABLES, Ltd. May 12, 1939, No. 14239. Convention date, June 11, 1938. [Class 40 (v)] In order to prevent confusion due to reflected or refracted signals forming spurious course-lines, a navigational run-way XY is defined by two sharplydirected overlapping beams A, N, A<SP>1</SP>, N<SP>1</SP> confined to the limited angular zones 11, 14 and 15, 18, and navigational signals are provided outside these zones by less sharply-directed lobes P, Q. The true course is unaffected by any reflecting object, such as 20, outside the angular zones, although navigational signals can still be received outside these zones. Preferably the course-line is marked by complementary A-N signals, and each of the sharplydirected beams is produced by two V aerials radiating 3-metre waves modulated at 500 c.p.s., the aerials producing the beams A, A<SP>1</SP> being energized simultaneously with those producing the beams N, N<SP>1</SP>, so that the same keying signal is heard irrespective of the direction of approach. The figure-of-eight field P, Q is produced by a central energized aerial and two lateral keyed reflectors which produce only a small field-strength along the course-line. The same wavelength is used as for the beams but modulated at 2,000 c.p.s., the lobes P, Q being keyed by A-N signals which are not quite complementary so as not to produce another continuous dash on the course line ; alternatively two separate arrays may be employed to produce the lobes P, Q. The beams and lobes may be distinguished by the use of different carrier frequencies or keying signals.