GB787797A - Improvements in or relating to electron velocity modulated tubes - Google Patents

Abstract

787,797. Velocity modulated tubes. STANDARD TELEPHONES & CABLES, Ltd. May 31, 1956, No. 16822/56. Class 39(1). [Also in Group XL(c)] In a velocity modulated tube of the type in which an electron beam is projected diametrally across a coaxial line resonator and designed as a frequency modulated oscillator, the frequency modulation voltage is applied between the inner and outer conductors of the line, the coaxial line resonator being coupled via a disc seal 10, Fig. 3, and clamp 16 to the outer conductor 15 and via a top cap 11 to the inner conductor 19, of an external coaxial line resonator 13, the inner conductor 19 being divided into two portions capacitively coupled together by a condenser 20 comprising conductive flanges and a mica disc 26 and disposed at a h/f voltage maximum at the centre of the tuning range, the inner conductor part 19 being formed as a coaxial line 23, 24, the frequency modulation voltage being applied via transformer 21 between conductor 24 and external earthed conductor 15. Escape of energy along coaxial line 23, 24 into the modulation circuit is prevented by increasing the diameter of conductor 24 to form a choke section of low characteristic impedance, the portion adjacent dielectric plug 30 being a #/4 section of high characteristic impedance. Conductors 23, 24 are effectively shorted for high frequencies at the end adjacent capacitor 20 by continuing conductor 24 through an aperture in mica disc 26 and securing it to inner conductor 18. The centre conductor of the internal coaxial line resonator is mounted within the envelope as described in Specification 664,281, and the external resonator is tuned to the centre frequency of its range by piston 14 output is taken from the external resonator by loop 28 and coaxial line 29 and permanent magnet 12 focuses the beam. The electron gun comprises a cathode, control grid and screen grid.