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Show it.illrri 1 - li. iioui,'iiis Wat-amp. Ciluur oi Kadiu Merchandising. J T 1 1 1 ' 1 U L3eJ 1 r r en 1 t u Ljt- Lill! I -01 rn 1:1:1:- 1 P " 1 1 1 4r The Reflex, Circuit Using Four Tubes. The Last One Acts as the Detector While the First Three Play Double Duty and Supply Three Stages of Radio Frequency and Two Stages of Audio Frequency Amplification. By J. L. GOLDSMAN, I.R.E.A.I.E.E. Very much discussion has been carried car-ried on as to the practicability of the so-called reflex circuit a circuit designed, de-signed, developed and patented In April and November of 1917 by Marlus Latour, a French radio engineer. The circuit consists of four tubes, the first three acting as radio frequency fre-quency transformers, which are designed de-signed for limited wave lengths, the last tube acting as a detector. After the rectification of the high frequency oscillations the current Is led back to the primary winding of an audio frequency transformer and thence to high voltage and the filament The secondary winding of the transformer trans-former is placed In the grid circuit of the second tube, which consequently amplifies the audio frequency oscillations oscilla-tions at the same time as the radio frequency. The latter does not pass through the secondary windings, but Is shunted across a fixed condenser of approximately .002 mfds. The audio frequency currents are amplified by the second tube and pass through the primary winding of the second audio frequency transformer. The secondary winding of this transformer Is In the grid circuit of the third tube. This tube also amplifies the audio frequen- cy currents which flow through the telephones, which are included in the plate circuit of the third tube. Fixed condensers are placed across both primaries pri-maries and both secondaries of the audio frequency transformers to prevent pre-vent the windings from Interfering with the high frequency oscillations flowing simultaneously In the same circuit. cir-cuit. This circuit Is complex and difficult to control due mostly to capacity ca-pacity effects, etc. In lieu of the radio frequency transformers I substituted sub-stituted oscillation transformers (.0004 variable condensers and approximately approximate-ly .2 millihenry inductance). Better results were obtained. Great care must be taken to prevent understage radio frequency transformers acting as grid condensers and rectifying the high frequency oscillations before they reach the detector tube. This Is common com-mon with many radio frequency sets on the market today. Atlanta Journal was heard In Toledo with this circuit using an aerial, but from all indications indica-tions the standard five-tube radio audio frequency circuit Is preferred where a loop Is practical. Another circuit cir-cuit along these lines Is now under test using only three tubes and with a few changes in wiring greater audibility audi-bility has been obtained. (Copyright, Radio News.) |