Notes on Reaction

Radio Record, Volume II, Issue 7, 31 August 1928, Page 28

Notes on Reaction

EE eee HUARLY Reinartz circuits gave reaction control that was very subject to hand-capacity effects that were not properly suppressed even by the use of metal panels, Later modifications of the Reinartz circuit have done away with this difficulty by connecting the reaction coil direct to the plate of the valve, and interpo ing the reaction condenser between this coil and earth, so that provided the moving plates of the latter are joined to earth, a metal-lined panel can be used to remove any lingering traces of hand-capacity effects. If this type of citeuit, which is perhaps the most satisfactory of all, be adopted, it is found that the tuning ean be made sufficiently independent of the reaction control to make ad-" justment of the receiver easy, though it is usual for the setting of the reaction condenser to vary widely over the different parts of the tuning range, This, however, is not found to make tuning difficult, and so is of but little practical importance. It is found in practice that the greatest degree of . independence between the controls is attained when the reaction condenser is not too small. It is therefore easier to handle a receiver in which the reaction coil is small, or loosely coupled to the tuned circuit, but is fed through a condenser of maximum capacity, perhaps 0.00038 mfd., than one in which the same degree ‘of reaction is obtained by the use of quite a small condenser in conjunction with a large coil. The remarks here made are equally. applicable to receivers in which a stage of high-frequency amplification precedes the detector, even although in this case critical reaction should be required less frequently.