Patent GB-722343-A (GB)
Title: Improvements in or relating to standing wave indicators for wave guides
Inventor: BURR RONALD LAWRENCE
IPC: G01R1/26
Filed: 1952-04-03
Abstract: 722,343. Current and voltage measuring. DECCA RECORD CO., Ltd. April 7, 1953 [April 3, 1952], No. 8693/52. Class 37. [Also in Group XL (b)] In a standing wave indicator wherein a carriage is traversible along the face of a rectangular wave-guide carrying a tongue with a probe extending therefrom by an adjustable amount through a longitudinal slot in the wave-guide, the probe being connected over a coaxial line to a radio frequency detector indicator, guide rails of durable metal are provided for the carriage on the upper surface and side faces of the wave-guide, and the carriage is firmly urged into its seating on the guide rails by a spring-loaded member bearing on a separate guide rail spacedly mounted from the waveguide and parallel to its axis. A length of rectangular wave-guide 10 (Figs. 1, 3) is mounted on a base 11 with its broad surface uppermost, along which extends a longitudinal slot 12 tapered for a distance of half a wavelength from each end to a width 1/#2 of that of the central part. A probe 26 extends into the wave-guide slot through a tongue 25 and rectangular section guide rails 14, 15 are secured to the outer surface of the waveguide along the two upper edges, to support a carriage laterally traversible on ball-races 19, 20, 21, 22, 23, 24 (Figs. 4, 5, 6), engaging the upper and side surfaces of the guide-rails to accurately locate the carriage with regard to the axis, the slot, and the inside surfaces of the wave-guide. A U-shaped member 27 horizontally pivoted to the carriage at its closed end is upwardly spring-loaded to urge a friction roller 31, vertically above the centre of gravity of the carriage and mounted on a rotary spindle 32 carried by the arms 30 of the U-member parallel to its pivot, against a fixed guiderail 33 (Figs. 1, 3) mounted parallel to the slot 12 on flanges 34' fixed to the wave-guide whereby the carriage is held firmly on the guide-rails for lateral motion parallel to the guide axis. A knob 35 mounted on the U-member rotates the friction roller 31 through a slow-motion drive to traverse the carriage and the probe along the slot into a position accurately measurable by a linear scale 37 on rail 33 and a vernier 38 on the carriage, or by a dial gauge 41 clamped by a bracket 39 to the guide rail 33 so that its feeler 42 engages the carriage. A pair of choke grooves (not shown) are formed wavelength deep (or wide) in the underside of the carriage, with their inner sides spaced “ wavelength from the line of the slot. The probe assembly (Fig. 7) mounted on the carriage comprises a two-part outer casing 45, 46 joined by a screw locking- ring 47, having at its upper end a threaded micrometer thimble 44 carrying a central rod 43 reduced at its lower end to form the probe 26 whose depth of penetration into the wave-guide slot is thus adjustable. The rod 43 is surrounded by a flanged sleeve 49 threaded to the casing 45 at its upper end and to a cruciform member 52 attached to interconnected sleeves 50, 51 at its lower end, the latter of which is provided with spring contact fingers 55 engaging the rod, which is centred in an insulating bush 48, so that the probe is effectively terminated in a short-circuited half wave coaxial stub. The side arms 53, 54 of the cruciform member respectively extend through an insulating bush 59 within a side-member 58 of the casing 45 to a crystal detector indicator 57 (Fig. 1) and through a side member of the casing to an adjustable short-circuited coaxial stub of the kind described in Specification 700,438, [Group XL (b)], wherein a dielectric sleeve 62 carried by a thimble 63 threaded to the member 61 is movable in or out of the coaxial line formed by arm 54 and member 61 for tuning.