Patent GB-401921-A (GB)
Title: Improvements in or relating to thermionic valve oscillatory systems
IPC: H03B5/34
Filed: 1933-02-06
Abstract: 401,921. Valve generating circuits. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.- (Assignees of Tunick, H. ; 7, Wainwright Street, Rye, New York, U.S.A.) Feb. 6, 1933, No. 3648. Convention date, Feb. 6, 1932. [Class 40 (v).] Comprises a crystal-controlled oscillator of the kind in which the output circuit is associated with the frequency-determining circuit by virtue only of electron coupling within the valve, thereby rendering the frequency independent of load variation. The crystal 2 has two pairs of electrodes, one pair 60 connected to the outer grids 8 of a push-pull pair of valves 1, 3, and the other pair 62 connected to their inner grids. Capacity coupling between the grids and their leads is prevented by earthed screens 70, the effective back coupling being through the crystal 2. The output impedance 14 may be connected between the plates, and tuned to the crystal frequency or an odd harmonic thereof; or the impedance 14 may be connected between the cathode and both plates and tuned to an even harmonic. Supply voltages are applied through centre-tappings on a choke 76 for the inner grids, on a resistance 74 for the outer grids, and on the output impedance 14 for the plates. The Specification as open to inspection under Sect. 91 describes various other forms of crystal-controlled oscillators. As shown in Fig. 1 (Cancelled) the crystal 2 shunted by a leak 16 is connected between an inner grid 4 and cathode 6, and a tuned circuit 12 is connected between an outer grid 8 and battery 22, the inter-grid capacity being supplemented if necessary by an external capacity 34 to maintain oscillations in the circuit 12 at the frequency of the crystal 2. The output is taken by a tuned circuit 14 or other impedance connected in the anode circuit of the valve. The crystal may be connected between the two grids (Fig. 3 Cancelled, not shown) and a further shielding grid may be interposed between them. The tuned circuit 12 may be transferred to the inner grid circuit, and the crystal 2 shunted by a choke coil transferred to the outer grid circuit (Fig. 4 Cancelled, not shown). The cathode, or the outer grid, or the plate may be earthed ; and the plate may be connected to a tapping on the coil of the tuned output circuit 14. Push-pull pairs of valves may be employed with the crystal connected between the inner grids, or between the outer grids, and with centre tappings for connexion to cathode, grid bias, or plate supply batteries (Figs. 5 and 6 Cancelled, not shown). The output circuit may be tuned to an odd or even harmonic of the fundamental frequency. In Fig. 9 (Cancelled) a magnetic back coupling 108 is employed between the circuits of the two grids, the inner grid circuit 110 being tuned and connected to the grid 104 through the crystal 2. The cathode is connected to a centre tap 114 on the tuned circuit, and the capacity between the crystal electrodes is balanced by a capacity 112. In a modification similar to the accepted figure but using a single valve (Fig. 7 Cancelled, not shown), a pair of electrodes on one side of the crystal are connected together and to the cathode. A space-charge grid is employed and a further screening-grid between the grids 4, 8. In a further arrangement, Fig. 7a (Cancelled), the plate is associated with the crystal electrode 82, the inner grid with the electrode 84, and the screen-grid with the screening system 70. This subject-matter does not appear in the Specification as accepted.