Radio broadcast .. (1922-30)

The Super-Autodyne 385 its adjacent 210 transformer. This C battery is 3 volts, and may be placed in the cabinet under the sub-shelf, since its leads should be short. It had best be wrapped in paper to prevent shorting on any of the wiring. For UV-2OIA tubes, these leads may be shorted and the battery eliminated entirely if the amplifier will oscillate without it. The remaining battery leads are brought out through a color cable, which should be coded in accordance with the data presented on page 1034 of the April RADIO BROADCAST. Unfortunately, there are a few manufacturers who have not yet adopted this coding for their cables. In Fig. 6, the colors of the various wires in the cable used for different voltages are given. This was for one particular make of cord, used on an experimental set. It will be noticed that the black lead with red tracer is used for three connections, which are made between the batteries themselves by means of other wires. ACCESSORIES AND TESTING ASSUMING the receiver to have been wired, it is ready for test. The additional material required is as follows: 6 Radiotron tubes, uv-2OiA, or uv-icjg. ov-3 De Forest tubes may be substituted for 199*5, but will require a standard-base socket shelf. i A-battery. This may be a storage battery, 6 volts, 90 ampere hours for uv-2oiA*s, or it may be the battery used in an auto, tapped by means of Lynch Leads. For dry cell tubes, three dry cells may be used, or, better yet, for home installation six in series-parallel. 1 B-battery. For permanent installation 90 volts, of large size 22, or 45 volt batteries should be used. For portable work, 6y| volts will be sufficient, of medium or small-size batteries, since the current drain is but 12 milliamperes for 20 1 A tubes, and 9 milliamperes for 1995. (90 volts will give only slightly more volume than (f]\, so it is hardly worth while to carry around the extra 22-volt battery. 2 C-batteries. One 3-voIt battery required in the set box for the r.f. amplifier, and one 4^-volt battery for the a.f. amplifier. i Loop with center tap. Any good tapped loop may be used, or one may be made by winding 16 turns spirally on a form about 24 inches square, tapped at the center, with j inches between turns. This loop with eighteen turns, T\ inches apart, may be wound on the back of a cabinet large enough to hold the set, with the batteries beneath if desired. i Loud speaker. The small Amplion is recommended for portable work as it is a most excellent speaker, and delivers very good volume and quality. For home use, the Western Electric cone speaker is best, with its leads shunted by a .0075 mfd. condenser. i Phone plug. I Set Lynch Leads if the set is to be operated in a car,' using the starting and lighting battery. The Lynch Lead may be made up from any double conductor wire. Several types of wire can be used, but the flexible, rubber covered lead is recommended. The wires, which should be colored for ease in identification, should be scraped on one end, for connection to the filament posts on the receiver. The other end of the lead should be connected to a plug which will fit into the dashboard connection to the automobile storage battery. i 7 inch x 18 inch x 7 inch mahogany cabinet. 200 250 30Q 350 400 450 500 550 600 WAVELENGTH IN METEKS FIG. 12 Typical tuning chart of a super-autodyne. The curve marked "Loop S" is for the loop condenser with the switch in the "L" position. Only one curve is shown for the oscillator. The curve embracing the upper heterodyne points would parallel the one given, starting about four degrees higher at 250 meters and ending about thirty degrees higher at 530 or 540 meters CONNECTIONS THE A battery should be connected to its leads, one tube inserted in a socket, switch S2 closed, and rheostat R4 just turned on. If the tube lights, it should be moved from socket to socket to see that all A connections are correct. The positive battery lead should then be connected to the 845 and B 90 posts. If the tube lights, the wiring or assembly is faulty and should be checked. The tube should only light when the A battery is connected to the A leads. The remaining batteries may be connected, and the loop leads run to posts B i, 62, and 83. If the loop is spiral, Bi goes to the outside