GB631872A - Improvements in or relating to radio beacons - Google Patents

Abstract

631,872. Radio navigation. SADIR-CARPENTIER. June 25, 1946, No. 19023. Convention date, June 25, 1945. [Class 40 (vii)] An equisignal type radio beacon comprises a central aerial fed from a transmitter and two laterally spaced. aerials with means for alternately varying the characteristics of the lateral aerial circuits in phase opposition at a frequency of the order of audio frequencies. The laterally spaced aerials may or may not be energized. In the case where these are not energized no high frequency feeders are re. quired for the lateral aerials. Fig. 2 shows such a beacon wherein a transmitter 7 energizes aerial A. and the tuning of lateral aerials B and C is alternately varied by audio frequency modulator 6 which operating through transformer 5 causes diodes 3 and 4 to conduct during alternate half-cycles and alters the effect of the reflector aerials by damping the tuned circuits. The received modulation depth is zero along the axis and has the same value but differs in phase by 180 degrees at symmetrical points on either side of it. To identify to which side any deviation from course takes place the transmission from the central aerial may be modulated so that its modulation is in phase with that created to one side of the course and thus adds to it and subtracts from that received on the other. By inverting the phase of this modulation by keying means 8 at a low frequency and in dot-dash or similar rhythm standard equisignal indications can be obtained on the craft. Instead of diodes contact rectifiers may be used (Fig. 3, not shown) and instead of shunting the tuned lateral aerial circuits supplementary reactances may be alternately inserted and removed (Figs. 4 and 5, not shown). To obtain phase reversal of the lateral aerial currents with constant amplitude it may be arranged that the detuning effected when a rectifier is conductive is equal but opposite to that occurring when the rectifier is non-conductive. The inverter 8 may be inserted in the modulation frequency coupling to the lateral aerials instead of in the modulation feed to the central aerial. Fig. 6 shows the feed to one of the lateral aerials in a system in which the lateral aerials are energized. The characteristics of these aerials are modified by any of the means previously described (not shown in Fig. 6) at an audio frequency and phase reversing means 8 inserted in each feeder. The directly fed component of the energy may be adjusted in amplitude and phase in the coupling circuits so as to produce the desired signal when combined with that directly induced at C by aerial A.