Patent GB-160799-A (GB)
Title: Improved electric oscillation generator
IPC: H03B5/10
Filed: 1921-03-24
Abstract: 160,799. LÚvy, L. March 29, 1920, [Convention date]. Thermionic oscillation generators; thermionic modulating systems and apparatus; directive signalling. - Relates to oscillation - generators of the " multivibrator " type shown in Fig. 1, in which two relays 1, 2 are supplied from a single battery, the controlling circuit of each relay being crosscoupled to the secondary circuit of the other relay by means of external capacities 13, 14. The characteristic feature of such a system lies in the fact that the output is extremely rich in harmonics, those of the fundamental frequency not being predominant. According to the present invention, the efficiency of such an arrangement for the production of oscillations of a definite frequency is increased bv the inclusion of auxiliary circuits of the type shown in Figs. 1<a>, 1<b>, or 1<c>, capable of free oscillation, whereby the energy output of the system can be tuned to a given fundamental frequency carrying relatively few harmonics. More than two valves may be similarly arranged in cascade; and the circuits may be coupled magnetically, as shown in Fig. 6, instead of capacitatively as shown in Fig. 1. As shown in Fig. 4, the two resistances 9, 10 of the basic arrangement are replaced by oscillating circuits 15, 16 forming aerials 25, 26 earthed at 27, 28. By regulating the length of the aerials experimentally so that current loops are formed at the points 27, 28, and arranging the distance between these points to be of the order of half the wave length, directive transmission according to the Blondel method may be achieved. In this arrangement impedance coils 29, 30 replace the original grid discharge resistances 17, 18, thereby avoiding too great a charge on the grid condensers 18, 14. Fig. 5 shows a combined telegraphy and telephony set. Here the radiating-valve 2 is considerably more powerful than the valve 1; it may consist of a group of valves in parallel. The microphone transformers 39 may be inserted at the points z, t or z', t'. The corresponding microphonic variations in the plate circuit of valve 1 give rise to voltage effects across the choke coil 33, which are impressed on the grid of the power valve 2, and thence to the aerial circuit 16, 23, 24. A switch 42 connects the primary of the transformer 39 with a microphone 40 or to an ordinary telephonic line 44, through an amplifier 43 if necessary. The filament battery is replaced by a generator 48, and the plate tension is supplied by a continuouscurrent or ultra-acoustic alternator 34 protected by a condenser 36. A condenser 37 prevents short-circuiting of the generator 34 but passes high-frequency pulses in the plate circuit. Telegraphic signals may be sent by means of a key 46, which short-circuits the arid-circuit coil 30 of the valve 2. This key may be actuated at high speed, for example by a Wheatstone transmitter. In a cascade arrangement, the plate circuit of each valve is coupled selectively to the grid circuit of the next valve, the plate circuit of the last valve being similarly linked with the grid circuit of the first valve of the series.