GB178992A - Improvements in and relating to radio transmitting systems - Google Patents

Abstract

178,992. British Thomson - Houston Co., Ltd., and Alexanderson, E. F. W. Feb. 15, 1921. Multiplex signalling; transmitting systems; magnetic modulating systems; aerials.-An arrangement of two or more antennae in close proximity, for radiating simultaneously at different wave-lengths, is characterized by the provision of an inductive or magnetic coupling which is adjusted so as to partly neutralize the mutual capacity effect of the aerials. The aerials A, B, preferably of the type described in Specification 130,064, are supplied with high-frequency current from separate sources 1, 2, the frequency of the latter being, say, less than that of the former. The value of the coupling-inductance 5 is so adjusted with respect to the capacity effect between the adjacent aerials A, B that the intermediate circuit A, 5, B is tuned to the frequency of the aerial B, which will then oscillate as if the aerial A were non-existent. The tuning of the aerial A must then be corrected to allow for the effect of the mutual inductance and capacity. A frequency trap 7, tuned to the frequency in the aerial A, is placed as a shield in series with the magnetic modulator 6 across the source 2. Alternatively the circuit A, 5, B may be tuned to a value intermediate the frequencies of the aerials A and B, in which case a frequency trap 8, tuned to the frequency of the aerial B is also employed as shown. Instead of the inductance 5, a magnetic coupling (preferably independent of the tuning-coils 3, 4) may be provided between the aerials and be similarly adjusted so as to neutralize the mutual capacity effect. The system may be extended to three or more associated aerials. Reference has been directed by the Comptroller to Specification 169,143.