GB463238A - Improvements in or relating to high frequency signalling systems or apparatus - Google Patents

Abstract

463,238. Transmission systems. STANDARD TELEPHONES & CABLES, Ltd. Sept. 18, 1936, No. 25446. Convention date, Oct. 12, 1935. [Class 40 (iv)] [Also in Groups XL and XXXVI] Relates to means for modulating and demodulating carrier-waves which are propagated as displacement currents along a dielectric guide line. In Fig. 9, one or more crystals are connected in series with a choke 51 to rectify modulated waves, the extension 52 acting as an aerial or pick-up. Or the crystals may be disposed along a transverse arc of the guide. Or they may be located outside the guide in a cap S as shown in Fig. 12. In Fig. 14, the crystals are arranged radially around a central ring 56, the adjustable pistons 58, 59 providing a balanced impedance coupling between the guide and the two-wire transmission line on the left-hand side of the Figure. Other forms of balanced coupling are also described. The crystals may be replaced by thermo-electric rectifiers. A reflecting piston such as 65, Fig. 22a, may be used in combination with an iris diaphragm 70 which controls the admission of the waves to the " chamber " containing the crystals. Fig. 24 shows a method of heterodyne reception, a local oscillator f2 beating with the incoming signal frequency f 1 to form a standing-wave system in the transverse chamber between two pistons. A valve may be mounted inside the guide as shown and used either as a heterodyne oscillator, as a super regenerator, or to provide ordinary reaction. In Fig. 28, the pick-up wires or " aerials " 97 are connected to transverse Lecher wires 90, which are tuned by bridges 92, 93 and fed with local oscillations from a source 95. The rectifying crystal 94 is bridged across the wires, and feeds a receiving set Glow tubes of the cold-cathode type may also be used as rectifiers. As shown in Fig. 30, one such tube 106, set to a critical state of ionization by the battery 107 modulates the carrier wave from the source 104 by speech or television signals applied at SM. A similar tube 106<1> acts as a demodulator. Or the modulating currents may be applied to field coils surrounding the guide. Fig. 38 shows a multi-electrode valve in which each grid is connected to the wall of the guide by radial conductors 118 which pass through holes in a cylindrical anode 119. Fig. 41 shows a Barkhausen-Kurz oscillator with a change-over switch arranged either for transmission or reception.