Patent GB-650668-A (GB)
Title: Improvements in or relating to electron discharge tube mounting arrangements
IPC: H03F3/54
Filed: 1946-02-01
Abstract: 650,668. Electric discharge apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Feb. 1, 1946, No. 3324. Convention date, April 6, 1944. [Class 39 (i)] A mounting arrangement for a vacuum tube of the " lighthouse " type comprises a hollow rectangular metallic housing across which housing a first and a second contact plate extend, each being attached to at least one wall of the housing and each having an aperture therein with a plurality of contact fingers surrounding the edges of the respective apertures and serving respectively to engage the grid ring and anode cylinder of the tube, and a cover-plate for one end of the housing supporting means for exerting pressure upon the tube. In Fig. 2, which shows the oscillator stage of a superheterodyne receiver the tube is mounted inside the square housing 3<SP>1</SP> and the square grid contact plate 2<SP>1</SP> comprises a plurality of silver-plated beryllium-bronze spring fingers 25 engaging the metallic grid ring. The cathode shell S is connected by spring fingers 251 to the end of a quarter wavelength piece of cylindrical metallic tubing 27 supported at its base by a plate 60 over which a cover-plate 49 is positioned. The anode plate 5 encloses a circular metallic plate 5<SP>1</SP> with which it is in capacitive relationship through a mica spacer M. The circular plate 5<SP>1</SP> has a plurality of contact fingers surrounding a hole in its centre and engaging the anode cylinder. Plate 5 has a hole 35 drilled in it to take the anode lead L and anode resistor 59. The housing 31 has three threaded holes accommodating coaxial line tuning stubs 4<SP>1</SP>, 11, &c. which tune the anode, grid and cathode circuits. The output adjustable tap for the oscillator comprises a movable plate 37 which is movable between the front wall of the housing 3<SP>1</SP> and a pair of flanges 39, Fig. 7. The plate 37 has an aperture through which the probe 13 enters the interior of the housing 3<SP>1</SP> and carries a threaded tubular section 43 co-operating with a spring socket 45 to form a coaxial line stub connected to the output cable. The tube is maintained in position by pressure from a " Bakelite " (Registered Trade Mark) rod R, one end of which engages the insulation stub at the end of the tube and the other end of which is in contact with a spring 51 exerting pressure on the rod. The rod R is accommodated in an opening in a "Bakelite " rod R<SP>1</SP> fastened by screws to the cover-plate 49. The rod R is maintained in position by a screw 52. The cathode is provided with a bias resistor mounted on the tube socket and connected between the cathode and the shell S. The amplifier stage is similar to the oscillator stage except that the grid contact plate extends entirely across the interior of the housing and the probe makes direct contact with the anode plate instead of being capacitively coupled. The converter stage also includes a " lighthouse " tube positioned within a grounded hollow rectangular metallic casing and the anode is byepassed for radio-frequency voltages by a built-in 6 ÁÁf capacity provided between the housing cover-plate and the spring fingers making connection with the anode ring and supported from the cover-plate by three Isolantite insulating means.