GB152693A - Negative and positive resistance vacuum tube devices especially for use in wireless telegraphy - Google Patents

Abstract

152,693. Taggart, J. Scott-. July 25, 1919. Thermionic relays; electric oscillations, producing; wireless telephony.-In an arrangement of vacuum tubes which may be adapted for use as an amplifier of wireless signals, or a wireless telephone receiver or transmitter, two three-electrode valves are provided, the anode of the first valve being connected to the grid of the second and the anode of the second valve being connected to the grid of the first. The cathodes 1, 4, Fig. 1, are connected together, and across the grid 2 and the filament 1 is connected a variable high resistance F. If a conducting circuit is connected across D, and the potential of anode 3 is increased with respect to filament 1, the potential of grid 5 will be increased, and a corresponding increase of current will result in circuit 6, E, F, 4. This will cause a decrease in the potential of grid 2. Increasing the potential of anode 3 therefore has two opposing effects upon the anode current of the first valve, one tending to increase it, and the other to decrease it by reducing the potential of the grid 2. The value of resistance F varies the relative magnitude of these two effects, which determines whether the device has a negative or a positive resistance characteristic. In order to increase potential variations on grid 2, two or more valves acting as amplifiers may be used in series instead of the single valve 4, 5, 6. Fig. 2 shows the arrangement adapted by wireless reception. An oscillatory circuit K is coupled to the aerial system L and included in the anode circuit of the first valve, a telephone M also being included in series. In Fig. 3, the arrangement is shown adapted for use as a wireless telephone transmitter, the valve A having an additional grid 7 connected to the cathode 1 through the secondary of a transformer 0, the primary of which is connected to a microphone P. This modification may also be adapted for receiving, the receiving oscillatory circuit being connected across the cathode and the additional grid of the first valve, while the telephone is connected in the anode circuit thereof, or the receiving oscillatory circuit may have one side connected to the second grid of the first valve, and the other to a point on a resistance in the anode circuit of the first valve. Used with a negative resistance characteristic, the device as .described with reference to Fig. 1 may be utilized to neutralize grid or anode circuit losses in threeelectrode valve circuits, by connecting the anode circuit of the negative resistance device in parallel with the grid or anode circuit of the said threeelectrode valve circuit. In general the positive resistance of a circuit may be lessened by placing said circuit in the anode circuit of valve A. One of the Provisional Specifications states that instead of using two separate vacuum tubes a single duplex tube may be used. The other Provisional Specification states that the device may be used as both a current and voltage amplifier, and by connecting an oscillatory circuit in series with the first anode circuit it will act as an oscillation generator.