GB546238A - Improvements in or relating to direction finding radio beacons - Google Patents

Abstract

546,238. Directive wireless systems. AGABALTIC RADIO AKTIEBOLAG. Dec. 5, 1940, No. 17323. Convention date, Nov. 28, 1939. [Class 40 (v)] A transmitting beacon for providing an equisignal course line comprises a pair of aerials connected at spaced points to a feed line, a switch operated by complementary signal currents being arranged to short-circuit the line at its connection to one of the aerials. Means may be provided for avoiding key clicks. The shortwave source 10 is connected by a line 11 to two dipoles 12, 14 spaced apart about a quarter wave length or an odd multiple thereof. When both are energized directly, radiation is a maximum to the right, and a minimum to the left, the polar diagram being approximately a cardioid. When the switch 16 is closed by the relay 17, the dipole 14 is not directly energized and the polar diagram is reversed. An equi-signal course is thus set up in a direction perpendicular to the plane containing the dipoles 12, 14. Relay 17 may be controlled by a cam 26 on a rotary shaft operating a switch 29. In order to avoid clicks in the receiver as the switch opens and closes, the source 10 is short-circuited at these moments by a condenser consisting of fixed plates 32, 33 and movable plates 36, the latter being formed as suitably-placed lugs on a disc fixed to the cam shaft. In a modification (Fig. 8, not shown) the lugs 36 operate a switch which is arranged to impose momentarily a prohibitive bias on the grid of the output valve of the source 10. The dipoles may be replaced by open quarter-wave aerials, one of the wires of the line 11 being connected to an earthing net (Fig. 6, not shown). The Specification also describes known arrangements in which a source energizes an open aerial and a frame aerial, the feed to the latter including either a receiving switch, or a resistance bridge which is unbalanced in opposite direction by operating a shorting contact placed across part of the resistance in one of the arms (Figs. 1 and 2 not shown).