| 摘要 |
1,225,489. Radio direction-finders. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 16 Sept., 1968 [3 Oct., 1967], No. 45065/67. Heading H4D. The direction of a transient radio signal (e.g. associated with a nuclear explosion) is determined by apparatus comprising three non-directional aerials N, S, W (Fig. 1, not shown), means operable by signals derived from the aerials for determining the order in which the aerials receive the transient signal, and means for determining the time interval between the receipt of the transient signal by the first two aerials to receive it. Two apparatuses may be provided to fix the position of a nuclear explosion. Each aerial is preferably a vertical aerial at the apex of an equilateral triangle and is connected by emitter-follower, transformer and cable means to a gate 8 to afford a positive output. A circuit 11 is triggered by a circuit 10 if the transient exceeds a predetermined level (e.g. 3 volts/metre) and each circuit 11 is connected to a "first-arrival" trigger circuit 12 and a " second-arrival " trigger circuit 13. Circuit 12 triggers if the field-strength at any aerial exceeds the predetermined level but circuit 13 triggers by such an input only if it has first been primed by prior triggering of circuit 12. Each aerial has associated coincidence gates, e.g. 15, 16 with aerial N so that one lamp of lamps 22, 23, 24 shows the "first-arrival" aerial and one of lamps 25, 26, 27 shows the "second - arrival" aerial. Time interval measurement is by counter 28. Trigger circuits 11, 12, 13 are bi-stable and are reset after each received transient by the trailing edges of pulses from generators 40, 31. The gates 15 to 20 are also bi-stable but are reset manually by a pulse from a circuit 42. In a modification all resetting is automatic, resetting pulses being gated by a signal from a detection apparatus as in Specification 1,165,331 (Division G1); thus there is rapid resetting after a large number of transients due to non- nuclear events (e.g. lightning) but the indication of a nuclear explosion transient is retained. Detailed circuits.-The aerials are vertical 1 metre rods mounted on 20 foot masts, each having a 1 metre square ground plane; a balanced cable compensator corrects for highfrequency cable loss by increasing low frequency attenuation; attenuators 5 equalize effective aerial sensitivities and a tunnel diode is utilized in each circuit 11 and has a clamping diode in its circuit to limit the voltage across the tunnel diode. Tunnel diodes are also used in other trigger circuits. |
