| 摘要 |
401,600. Wireless transmitting systems. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.-(Assignees of Usselman, G. L. ; Port Jefferson, Long Island, New York, U.S.A.) May 11, 1933, No. 13756. Convention date, June 22, 1932. [Class 40 (v).] The output from a radio-frequency transmitter 1, Fig. 1, is supplied to an aerial-feeding transmission line 8 by an inductive coupling 2, 3,the degree of coupling being adjustable by including variable series impedance coils 9, 10 in each side of the line 8, or a variable condenser across the line, or both. Preferably a second transmission line 7 is provided as an alternative to the line 8, a switch 4 being provided for changing over to a different wave-length. In this case, the coupling may be designed to suit one of the lines, and the variable impedances 9 provided in the other line. Series blocking condensers 6 are included in each line. The plate supply lead, which is connected to the mid-point of the transmitter coil 2, is also connected through a high resistance 5 to the coil 3 to prevent arcing between the coils. In Fig. 4, series coils 9, 10 and shunt capacity 21 are both employed, the capacity 21 being divided and its centre plate earthed through an adjustable coil 13. By tuning the coil 13 and condenser 21 to the second harmonic, energy of this frequency is byepassed to earth. A condenser 14 connecting the mid-point of coil 3 to earth also reduces the second harmonic, whilst in Fig. 6 the same purpose is effected by connecting each side of the transmission line 7 to earth through a line or coil 30 whose effective electrical length is one-quarter of the wave-length. Switches 15, Fig. 4, serve to connect the idle aerial and line to earth. |
