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394
Radio Broadcast
receivers to be had which embody rather complicated circuits, but are made for operation by an unskilled person and some of them are good, although they are not cheap.
Before attempting radio-frequency or any other involved arrangement, it is best, therefore, that you master the operation of your detector tube, for much can be accomplished by proper filament adjustments at various plate voltages. A potentiometer is of great value. And regeneration is not the sort of thing that takes care of itself — it requires skill.
negative terminal of the B battery may be used to connect that terminal to the negative terminal of the A battery (Fig. i).
THE PARTS NEEDED
Radio-frequency transformer. Vacuum tube (amplifier). Vacuum tube socket. Rheostat.
potentiometer (2oo-ohm). fixed condenser (.005 mfd.) It is possible to do without the potentiometer
FIG. 2
By employing the proper spider-web or multi-layer coils and their customary condensers, Fig. i is made into a short-wave, regenerative receiver with one stage of radio-frequency amplification
One of the greatest advantages of the threecircuit receiver is found in the variable coupling between primary and secondary. Properly employed, it is helpful in cutting out stations that would otherwise interfere. Do you know how to use it properly? If you feel that you are getting the best possible results from your receiver and want to increase your receiving range or desire to use a loop antenna, the following pointers on radio frequency may help you to avoid some of the pitfalls.
There is no use in trying to use radio-frequency unless you are willing to go to the trouble of using it properly, and more than one stage is recommended for use only by those who have mastered a single stage satisfactorily.
We are taking it for granted that you are using a potentiometer in connection with your detector tube, but if this is not the case, the wire connecting the centre post of R4 to the
and the fixed condenser but the results obtained are not as satisfactory.
A SIMPLE ARRANGEMENT
The circuit illustrated in Fig. i may be used in conjunction with any type of tuner and is comparatively easy to handle. It is a simple matter to add an audio-frequency amplifier or additional stages of radio frequency. By employing this arrangement with a standard multi-layer coil mounting, a number of variations are made possible with little loss of time.
The essential points in the circuit, at which the variations may be made, are represented (Fig. 2) by X, X1, X2, X3, X4, and X5, which correspond to the primary, secondary and tickler plugs of a standard coil mounting. X1 and X2 indicate the points between which the antenna tuning coil primary is plugged in. X2 and X3 are