Rectifying contact detector systems for very short electric waves

Abstract

Abstract 551,209. Wireless receiving apparatus. STANDARD TELEPHONES & CABLES, Ltd. (Westem Electric Co., Inc.). Feb. 4, 1941, No. 1452. [Classes 40 (iii) and 40 (v)] An ultra short wave crystal detector comprises a body of silicon of parity in excess of 98 per cent having one highly polished surface which is plated so as to form intimate contact over a large area with a conductor on which it is mounted. Fig. 1 shows a super heterodyne receiver embodying the invention, and comprising a metallic wave receiving chamber 1 having a front aperture formed by an iris diaphragm 16. Projecting through the rear wall of the chamber is a pair of semi-circular Lecher conductors 2 of a highly conducting alloy mounted in a member 24 which is slidably adjustable by means of a spindle 26 and bell-crank 23 for tuning purposes. A lens 42 of a suitable wax serves to concentrate in the chamber 1 both the incoming signal waves and waves from a local beat oscillator 3. The separation between the Lecher pair 2 and chamber 1 is such as to constitute a short circuit for the signal frequency but not for the intermediate frequency, which is taken by leads 5 from the inner ends of the Lecher pair to an I.F. amplifier 6, second detector 8 and A.F. amplifier 9. The first detector or mixer comprises a crystal 30, Figs. 3 and 4, mounted in a recess near the top of one of the Lecher conductors and co-operates with a wire 31 mounted in the other conductor. In a modification, the crystal and wire are contained in recesses in the ends of the conductors (Fig. 7, not shown). As shown in Fig. 3, the Lecher conductors 2 are separated by a strip of mica 17 and surrounded by a close-fitting dielectric sleeve 18 enclosed in a metal tube 19 joined to an insulating block 20 through which pass the leads to the subsequent stages. Also connected to block 20 is member 24 to which adjusting pressure is applied against the action of a spring 21, Fig. 1. The detector 30 comprises a machined block of silicon which is plated with silver or chromium where it is in contrast with its support. Also by means of using a reduced plating current it is stated that the active spots only of the working surface may be chromium plated so as to give permanent working spots which are easily located. The contact-wire 31 is of tungsten or a platinumiridium alloy and-may be tipped with an alloy of gold, silver and platinum. U.S.A. Specification 937,284 is referred to.

Inventors

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