Radio broadcast .. (1922-30)

706 RADIO BROADCAST ADVERTISER screw machine products — brass For plugs, jacks, clips, condenser and transformer parts, etc., BRASS assures economy in quantity production. It also gives the right electrical conductivity and the mechanical accuracy essential to proper operation of radio sets and parts. COPPERS BRASS RESEARCH ASSOCIATION 25 Broadway, New York STATIC ; Without Loss of Volume ELIMINATE STATIC Enjoy perfect reception regardless of weather conditions. The Static Eliminator — the newest and most startling thins in Radio — cuts out practically all static without loss of volume! And in addition it will help increase selectivity, tune out local stations, sharpen signals, remove noises, lessen interference, and prevent re -radiation ! Use It with any receiving set — simply hook up according to our simple instructions and enjoy perfect reception unmarred by static. Satisfaction absolutely guaranteed — • ^*KI Money back if Elim «^j7 inator is returned _ ^Jl within 5 days. Miil your order Today. 627 ! : L Ml*. I!/: United Bank BldiCincinnati.O. the counter disk is correct for a two-inch disk. By means of the screw on the crank, and the counter, each turn of the crank registers one complete turn of the coil. It is easier to use two rings of heavy cardboard tubing of given diameter and half an inch in width, clamped on each side of the spokes with two pieces of heavy sheet metal, than to make various size wood mandrels. In this way, one mandrel serves for all diameter coils. Take care to center these properly on the form before winding. An excellent coil can be wound in this way. These coils give fine results in a RADIO BROADCAST "Knockout" receiver. MATERIAL REQUIRED i — 45-inch x j-inch metal rod for shaft (60 penny spike will do), i — Piece of hard wood f-inch wide and of diameter desired, i — Piece of hard wood 5 inches x i j inches (support for shaft), i — Piece of heavy sheet metal 3 inches x f inches for crank. 15 — 21-inch x A-inch spikes for spokes (with heads cut off). 2 — Pieces of brass bushing, j-inch inside diameter, j-inch wide, with set screws. i — Baseboard about 15 x 8 x f inches. i — Small wood disk about 2 inches diameter j-inch thick for counter, with some small fishing nails to go around periphery. 2 — Wood spools of same size (thread spools.) 2 — Pieces of A threaded rod 2 inches long. 2 — Pieces of brass or wood tubing (pipe stems) | inch longer than spools. 2 — Pieces of metal strip 4 x f inches wide to hold spools. R. S. HART, Pisgah, Kentucky. A HANDY BATTERY THROW-OVER SWITCH WHEN a vibrating magnetic rectifier, such as the " Homcharger, " is employed to charge the storage battery, it is necessary to observe the following procedure: To charge: 1. Disconnect battery from receiver. 2. Connect charger to line supply (no volts a.c., 60 cycles). 3. Connect battery to charger. To discharge: 1. Disconnect battery from charger. 2. Disconnect charger from mains. 3. Connect battery to receiver. To eliminate the clumsy connection and removal of clips, the author has devised a simple arrangement whereby the complete process of connection necessary to the proper charge and discharge of the baitery is controlled merely by the movement of a double-throw switch. The switching device is illustrated in the accompanying diagram, Fig. 7. The dimensions of the switch itself are unimportant, so long as the extra contact which connects the charger to the line supply is made large enough so that the switch blades connected to the battery are entirely clear of their contacts before the line supply is cut off. BERNARD SALZBERG, New York City. ECONOMICAL SUB-PANEL BRACKETS BEING suddenly faced with the necessity of making a pair of brackets for a sub-panel, I tried the following: Get from a good hardware or plumbing supply store, a piece of i*s-inch channel brass, |-inch wide. This will be shaped as shown in i, Fig. 8. Measure how far the bracket must project back from the front panel and add about two inches for support to fasten on to the front panel. At the point where you wish to bend the strip make a cut, perpendicular and square across, with a hack saw, merely cutting through the side walls as illustrated in 2, Fig. 8. Then, with a three-cornered file, widen the saw cut to a "V" shaped notch, as in FIG. 7 Tested and approved by RADIO BROADCAST FIG. 8 3. Be sure the angle at the bottom of the notch is one of 90° and that it is pretty accurately placed 45° on each side of the perpendicular. The bracket is now bent, as shown in 4. If your angle is correct, the top piece will project from the panel exactly square, and the weight on the subpanel will be supported nicely by the side walls of the notch as they come together. Of course, by regulating the angle of the filed notch, you may make a bracket that projects from the panel at any angle of more or less than 90° as you wish. This idea could be used in making sets with a sloping panel. To finish the bracket, fill the corner where the brass was bent, with solder. This prevents the bracket from bending back under pressure from beneath, such as is exerted when the foot on the subpanel rests on a table or the bottom of the cabinet. R. L. DOUGLAS, Huntington Park, California.