Patent GB-223615-A (GB)
Title: Improvements in and relating to electric signalling apparatus, particularly for wireless reception
IPC: H03F3/48
Filed: 1923-04-19
Abstract: 223,615. Taggart, J. Scott-, and Radio Communication Co., Ltd. April 19, 1923. Thermionic amplifiers and detectors.-Comprises various modifications in dual amplification circuits comprising two or more valves. The circuit shown in Fig. 1 comprises a valve V<2> operating as a dual amplifier, and a valve V<2> operating as a low-frequency amplifier. The grid of the valve V<1> is connected directly to the aerial inductance, and the tuned anode circuit L<2>, C<3> is reactively coupled to the aerial. A crystal D and the primary coil T<1> of a transformer are connected across the tuned anode circuit, and the condensershunted secondary coil T<2> is connected in the grid circuit of valve V<1>. The anode circuit of this valve also includes a transformer primary T" which transfers amplified low-frequency currents to the grid circuit of the valve V<2>, the loudspeaker or other indicator LS being :n the plate circuit of this valve, and shunted bv a condenser C<4>. A stabilizing-resistance R is connected across the high-frequency coil L<1>, or the low-frequency coil T<2>, or as shown across both coils. A highfrequency amplifying valve may be inserted between the aerial and the valve V<1>, its tuned anode circuit being coupled to the grid circuit of the valve V<1> either by an inductive, coupling, or through a blocking condenser. Fig. 4 shows a two-valve receiver in which both valves function as dual amplifiers. The first valve V<1> has a tuned anode circuit C<3>. T<5> coupled to the grid coil T<6> of the valve V<2>. A crystal D and transformer primary T' are connected across the tuned anode circuit L<3>. C<6> of the valve V<2>, and the secondary coil T<2> feeds rectified current into the grid circuit of the valve V<1>. The low-frequency current is amplified and transferred to valve V<2> through the transformer T<3>, T<4> and after further amplification passes through the indicator LS. The transformer primary T<3> may be connected between the anode of the valve V<1> and the tuned anode circuit C<3>, T<5>, and the high-frequency potentials of the tuned circuit C<3>, T<5> may be transferred to the grid of the valve, V<2> through a blocking condenser. In this case, the secondary coil T<4> of the transformer is connected between the filament and grid of the second valve in series with a resistance or impedance, which prevents high-frequency energy from being short-circuited by the selfcapacity of the coil T<4>. Fig. 6 shows the combination of a dual amplifier V<1> and a detecting- valve V<2>. The tuned anode circuit of the valve V<1> may react on the aerial coil L<1>, and its potentials are applied to the detector valve V<2> through a condenser C<5>. The indicator LS<1> is connected between the anode of the valve V<1> and the tuned circuit L<2>, L<3>, the potentials across the indicator LS thus not affecting the grid of the detector V<2>. The tuned anode circuit may be inductively coupled to the grid circuit of the detector. Reference has been directed by the Comptroller to Specifications 131,092, 132,668. and 194,459.