NEW ENGLISH VALVE

Radio Record, Volume I, Issue 19, 25 November 1927, Page 15

NEW ENGLISH VALVE

FOR RADIO FREQUENCY, A big English radio-parts manufacturing company is shortly marketing a new type of radio-frequericy valve which | will render neutralising unnecessary. The amplification factor is given as 110, with a filament rated at 6 volts ond a current consumption of .25 amperes. Neéutralising Faults. A London writer says: "It is well known that the most careful shielding of the components in radio frequency amplifier circuits is useless unless some. form of neutralisation is adopted, and even then the fact that the neutralising condenser cannot have the same phase angie as the inter-electrode capacity makes perfect balance impossible. Further, this neutralisation is only effective over a comparatively narrow band of frequencies, and requires. adjustment as the tuning changes if the set is to be kept at its most sensitive stable wciking point. Nentralising Unnecessary. "The new valve is designed to overcome the iriter-electrode capacity effect within the valve itself, and thus ueutralisatioa is unnecessary. "A fine mash grid is placed between a.‘standard type grid und the atrodea flat circular plate with dished edges. The grid and filament are supported by and connected to'a cap at «ne erd of the ‘glass tube, ‘aid the ancde end screening grid by a second cap at the opposite extremity. : Methed of Use. a ‘Tn use, the valve is mounted in special holder placed in a it-orzizontal -position, the grid and plate circuits being separated by screening boxes so arranged that the partition dividing them is in the same plane as the screening grid, and cut away suificiently to allow the glass bulb te pass throvgh. The partition is earthed and the scrcening grid connected to a suitable print in the B battery {about 80V}, so that a complete electrostatic screen-is formed. ‘About 120V. is then applied to the plate throngh a. suitable H.I. transformer or‘ tuned anode coupling. ‘The best type of coil to use is a smule layer solenoid wound with ‘litz? wire, scme form of ‘ficldless’ winding being employed. . "Thus the new vatves bring within reach an amplification of 30-50 per stage with absolute stability and maximum efficiency over a wide range of wavejJengths. A single stage jresents no particular coustrnctional difficulties, and a second or third may be easily added if required." !