Regenerative and Reflex Receivers
This file contributed by Kim Smith and The Radio Electronique.
One Tube Receiver
A single vacuum tube may be used as a detector for satisfactory headphone reception up to fair distances. A non-regenerative one-tube receiver with condenser tuning is shown in Fig. 1. The coil and condenser are chosen according to information given under Coil, Tuning, Sizes Required for. A similar non-regenerative receiver, but with variometer tuning is shown in Fig. 2. The receivers of Figs. 1 and 2 are both of the single circuit variety, delivering considerable power but having little selectivity.
Regenerative one-tube receivers are shown in Figs 3 and 4 The antenna circuit is loosely coupled in both of these types, the single circuit arrangement being a too powerful radiator to allow its use with regeneration. The circuit of Fig. 3 uses the usual tickler coil feedback. The receiver of Fig. 4 uses a plate variometer for producing feedback through the internal capacity of the tube. Both of these methods of obtaining regeneration are described under Regeneration, Methods of Obtaining.
This type of receiver employs regeneration in the detector stage by using any of the methods described under Regeneration, Methods of Obtaining. The most commonly employed system uses a variable tickler winding on a rotor mounted in one end of the coupler. The layout, wiring and specifications for such an outfit are shown. Distance Range: About 200 miles with two audio stages added. Selectivity: Fair. Audio Amplifier: Any amplifier shown under Receiver, Audio Amplifier for, may be added by connecting to wires at right hand side of diagram. Construction: Easy to build and wire. See Regeneration, Methods of Obtaining; also Coil, Tickler.
A tickler coil is a coil electrically connected in one circuit and coupled to another circuit so that energy from the circuit in which the coil is connected may be introduced into the circuit to which the coil is coupled. A tickler coil is used as shown in Fig. 1 to secure a feedback of energy from the plate circuit of a tube to its grid circuit for the purpose of causing regeneration. The tickler coil is connected in the plate circuit and coupled to the grid coil of the tube.
Tickler coils may be of either the variable type or the fixed type. The variable type, as in Fig. 1, is mounted so that its magnetic coupling with the main coil may be changed; usually by rotating the tickler coil. The variable coupling might also be changed by sliding the tickler one way or the other.
The fixed tickler coil shown in Fig. 2 is not movable in relation to its main coil. The effect of the tickler, or its effective coupling, is then controlled by a variable condenser or variable resistance, thus giving a capacitive or resistance control of feedback and regeneration. See Regeneration, Methods of Obtaining.