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A new valve development in Denmark.
Two views of the Renode valve.
Details of a new type of valve developed by A Schleimann Jensen of the Skandinavisk Robrfabrik have just been released. The valve is a radical departure from accepted practice and has no grid in the ordinary sense of the word. The arrangement of the electrodes is shown in Fig. 1.
Fig. 1. - In the Renode, the cathode K is surrounded by a shield Kc which has a slot to permit the exit of electrons.
It will be seen that the emitting cathode K is surrounded by a screen Kc, which has a lengthwise slit parallel to the cathode. The auxiliary anode Ha also has a slit of the same size in it. The electrons emitted by the cathode pass through the cathode slit and are formed by it into a beam, which passes through the slit in the auxiliary anode to the main anode A. Between the two anodes the beam passes between two deflecting plates X and Y.
In operation the cathode and deflecting plates are operated at the same potential while the anode and auxiliary anode are positive with respect to them. The cathode shield Kc, which is termed the concentrator, has a negative bias applied to it, and when this has a certain value the electron beam between cathode and anode is concentrated into a straight path shown at (a) Fig. 2.
Fig. 2. - Depending upon the potentials applied to the electrodes, the beam of electrons between cathode and anode can be made narrow as at (a), brush-like as at (b) or it can strike the deflecting plates (c).
When the negative bias is reduced, the beam widens out (b) and eventually some of the electrons hit the deflecting plates (c). This last condition is the one normally employed, and the application of HF potentials to the deflecting plates by a circuit such as that of Fig. 3 causes the beam to be deflected alternately towards one or the other of the plates. The particular plate towards which the beam is deflected at any instant collects in consequence an increased number of electrons and there is a rise in current in the external circuit.
Linear Detection
Fig. 3. - A push-pull input circuit for use with the Renode when it is operating as a detector.
With the circuit of Fig. 3, full-wave rectification is secured, and as regards the external circuit the action seems very similar indeed to that of the ordinary push-pull diode detector. As a result of rectification, a steady potential appears across the load resistance R, and its polarity is such that the deflector plates become negative with respect to the cathode. If the HF input be modulated, this 'steady' potential fluctuates with the modulation, and both plates fluctuate together at the same average potential, although their instantaneous HF potentials may be quite different. As a result. the anode current is varied at the modulation frequency. As regards the external circuit, the action is very similar indeed to that of the American Wunderlich valve, which, it will be remembered, is the equivalent of a push-pull grid detector. The internal structure of the Renode, however, and its internal mode of operation are quite different.
Fig. 4. - The detection characteristics of the Renode (A) compared with those of an HF pentode (B).
It is not essential to employ the Renode with a push-pull input circuit, and if the two deflector plates be joined together a conventional input circuit can be used. HF currents then appear in the anode circuit. and it is quite possible to obtain reaction effects. The curves of Fig. 4 show at A the input output characteristics, and at B those of an HF pentode, the vertical scale representing the deflection of a mirror galvanometer in cms. The linearity with the Renode is well marked, and it is claimed that it extends to an input of at least 1 Volt. As an HF amplifier the valve is also more linear than an HF pentode, and damps a tuned circuit to which it is connected to a lower degree, thus leading to improved selectivity. The stage gain obtainable is somewhat higher than with conventional valves, but not greatly so.
It is clear from the few details which are yet available that the new valve promises to be an extremely interesting development. As the illustration shows, the external appearance differs little from that of an ordinary valve, and the dimensions are presumably of a similar order.
Fig. 5. - The non-radiating valve has two false grids A and B, and a. cathode which is only half coated.
In addition to the Renode a further valve, this time of more normal design, has also been developed. This consists of a triode which has two- false grids, A and B (Fig. 5), inserted between the control grid and cathode. Only one-half of the cathode is covered with an emitting layer, so that grid B is round a blank cathode, while grid A surrounds an active cathode. It is claimed that by using this valve in the correct circuit, presumably some form of balanced bridge, full reaction effects can be secured without any danger of radiation from the aerial, even if the reaction control is mishandled. Here, however, details of the circuit are not yet available, so that it is too early to form any opinion on the value of the device.
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