Radio age (May 1922-Dec 1923)

12 RADIO AGE— "THE MAGAZINE OF THE HOUR" of two or three thousand ohm receivers. Figure 3 shows how all the connections are to be made, and the builder can mount the outfit as he pleases, either in a box with a panel front, or on a table or base-board. The method of winding the coil is shown at "B" in Figure 2. If this set is carefully constructed, the results obtained will surprise the most skeptical reader and with one step of amplification it will produce results equal to two steps of amplification on the vario-coupler and variometer set. The amplifier, however, should be of a specially designed circuit, which will be explained for those wishing to add it to their sets. Amplification for Reinartz Tuner. Figure 4 shows the method of adding one step of amplification to the Reinartz tuner. In this circuit a variable condenser is shown in place of the grid-leak and condenser. The use of either of these is optional with the builder. The variable condenser will give better tuning eflfects, but the set will work very well if the grid-leak and fixed condenser is used; in fact, the set from which these specifications were taken used the fixed condenser and grid-leak. The method of connecting the amplifier to the circuit is similar to that of the ordinary The head phones are refrom the circuit shown in 3 and replaced with the winding of ten to one GR/D LEAK fiiND CONDENSER Circuit, moved Figure primary ratio audio amplifying transformer. In the set from which these specifications were taken, this primary winding of the transformer furnished enough reactance to make the tube oscillate properly, but this is not always the case. If it is found that the filament has to be burned at a dangerous degree of brilliancy to produce the oscillations, then an extra inductance should be inserted in the circuit at the point marked "X" in Figure 4. If however, the tube is found to oscillate without crowding the filament, then this extra inductance "X" should not be inserted. If it is found that the inductance is necessary it can be made by making a small form similar to the one on which the two coils are wound, but much smaller, and winding six turns of wire of the same size as that used on the large coil. This has been found by experiment to be the correct number of turns and should not be changed. The secondarv of the transformer is RHEOiTAT VftHIABLE CoeiOENSEfi ■001 M.f. 6 VOLT A-BATTeny -li|i|i|»|i|i|iK 2 2 '4 VOLT B-Bt^TTBRy _ CiHOUNO FIQORE 3 connected to the grid and filament circuit as shown in Figure 4. The circuit shows only one set of "B" batteries used for both the detector and amplifier tube plates, but stronger signals may be obtained by adding another twenty-two and one-half volt "B" battery between the head phones and the battery shown on the drawing. This is shown in Figure 6. It is absolutely necessary to see that the positive side of the "B" battery is connected to the part of the circuit, which eventually gets to the plate. AER/AL and the negative side must always be connected to the filament. Another important thing is to see that the rotating part of the condenser "C" is connected to the aerial, and that the rotating part of condenser "D" is connected to the earth. The set will not give good results unless this is done. The connections to the aerial, ground, and batteries are taken out through the back of the case, to avoid using binding posts on the front of the panel, as this always makes an unsightly wiring job. Tf X TRMSFORMER f-L^ RifeosTOT pHoNes)] X2J4VOLT riGURE 4-. desired, however, binding posts can be put on the ends of the case and all connections taken from there, but if holes are drilled in the back of the box and hard rubber, or porcelain bushings are inserted for the wires to pass through, it will make a very neat looking job. The^paneH for the controls is best of bakehtc, hard rubber one-eighth of an.