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9o8
Radio Broadcast
following explanation, designate these respectively, as A, B, and C. "A" connects to the posts or jack prong on the super which leads through to the grid of the first detector tube, either directly or through the pick-up coil. A short inspection of the receiver will identify this lead. In the case of loop binding-posts, it is generally the upper one. "B" runs to the remaining loop post or prong. The connection leads through to the filament of the first detector tube. The upper part of the loop is now connected in the usual manner, exactly as the whole loop was before the change was considered.
"C" is now connected to one side of a variable condenser having a capacity not less than .00035 mfd. This will be sufficient, though if more convenient a larger condenser may be used. The condenser shown in the photograph (Fig. i) is a Freshman mercury condenser, capacity .0005 mfd. The other and remaining side of the condenser is connected to the plate of the first detector tube. These connections are shown diagramatically in Fig. 2, where A indicates the usual loop connections in the Haynes and other super-heterodynes, and B the regenerative system.
The experienced reader will immediately identify the resulting circuit as the Hartley system, which becomes an oscillator as the condenser, C2 is turned above the spilling over point. This system of producing oscillation is used in many transmitting stations. However, the receiving operator, utilizing regenerative loop reception should not permit the detector tube to oscillate. In this condition it is a radiator of interfering waves, which, though they are effective only over short distances, may still bother reception on another receiver located in the same building. Fortunately there is absolutely nothing to be gained by maintaining these oscillations, reception being impossible until condenser C2 is turned down.
Tuning the "super" is only slightly more complicated with the regenerative loop. As regeneration is built up, a slight retuning of the loop or oscillator dial will be required. Regeneration will be most effective on distant stations.
Fig. i shows this system adapted to the Haynes simplified super-heterodyne, described in the March, 1924, RADIO BROADCAST.
FIG. I
The regenerative loop in operation. Note the three leads from the loop. The control condenser is above the oscillator dial. Three stages of resistance coupling are plugged in on the detector tube of this superheterodyne. See January, February, and March, 1924, RADIO BROADCAST