GB302602A - Improvements in method and apparatus for the measurement of distances by means of electromagnetic waves - Google Patents

Abstract

302,602. Koulikoff, A., and Chilowsky, C. Dec. 15, 1927, [Convention date]. Distances, determining.- Relates to systems of the kind described in Specification 288,233 in which the transmission of a wavetrain from a local station serves to energize a distant station which thereupon retransmits a second wavetrain, the timeinterval between the emission of the first and the receipt of the return wavetrain serving to indicate the distance separating the two stations. According to the present invention transmission is periodically interrupted to allow reception to take place. Fig. 1 illustrates the arrangements at the local station. An oscillator valve 11 is coupled through coils 13, 7 to interrupt or modulate the radiation from a high-frequency generator 1 feeding the aerial 5. At the same time it is coupled through coils 14, 15 to a receiver valve 16 in such a way as to render the latter sensitive only during the intervals in which the generator 1 is quiescent. Fig. 2 shows the distant station. Incoming signals received on the aerial 23 are applied through coils 30, 40 to the grid of a modulating-valve 41, and serve to interrupt or modulate the outgoing or return wavetrain from the generator 1 destined to be received on the aerial 20, Fig. 1, of the original or local transmitter. The distance in question can be determined by varying the local modulation frequency until a maximum reception is obtained in the telephones 68, 69 of the local station. The modulation frequency then corresponds to the time taken by the wavetrain to travel to and return from the distant station. Or a minimum reception effect can be utilized, suitable correction being made in both cases for the time-constants of the respective circuits. Or the distance may be measured by the apparatus described in Specifications 227,801, 230,013; and 241,505, [Class 118 (ii), Signals], in combination with a ballistic galvanometer for integrating the total current received in a definite interval of time. The outgoing and return wave-trains may be of the same or different frequency. In a modified form the same aerial is used both for transmission and reception at the local station, whilst separate aerials are used at the distant station for reception and re-transmission. The method is applicable to determine the distance between ships at sea, between a ship and the coast, between an aeroplane and the ground, orbetween running trains or a train and a station. A lighthouse or beacon, for example, may be fitted with several active or local transmitters, the corresponding distant or passive station being carried by a ship or aeroplane, to which the respective distances may be transmitted by special signal from the operator at the lighthouse- or beacon.