MOST boys are interested in wireless telegraphy, and it is possible for any one of them to make a simple apparatus by which they can “cut in” and receive any wireless message that happens to be passing through their particular zone.
The receiving set will require a number of different parts, but they are easily made—when one knows how.
For actual hearing you will need a telephone receiver of some sort. One may be bought for about seventy-five cents at an electrical supply house, or an old one, provided it is in good condition, may be used.
Next comes a “detector.” This consists of a wooden base about six inches long by four wide and an inch thick, on which is mounted a piece of silicon about the size of an egg. An insulated wire passed once around the silicon and then through two holes in the base will hold the silicon in position in the center of the block. Put a brass screw an inch long at each end of the block and “connect up” the silicon in the following way: First take a piece of No. 22 single-covered copper wire, scrape off a few inches of the covering, and wind this bare copper wire several times around a small round stick to form a spring. The bare end of the spring must be filed to a point and rest against one end of the silicon, while the other end of the wire is wound around one of the brass screws. Next, take a piece of ordinary insulated telephone wire, bare one end far enough to wind firmly around the free end of the piece of silicon, and then wind the other end of this wire around the second brass screw. This makes a metallic circuit through the silicon which will “make” or “break” with the touching or removing of the spring.
Detector.
Tuning Coil.
Next you need a “tuning coil.” This has a wooden base twelve inches by six and an inch thick. To make the coil itself a stick twelve inches long and one and a half inches in diameter—a piece of an old curtain pole will do—and wind carefully on it a half pound of the No. 22 single-covered copper wire. The end of this wire is fastened to the stick with a small tack, and it should be wound very evenly and closely. The last end is left free for a connection. After it is wound give the wire three coats of shellac, making sure that each coat is dry before another one is put on. When it is thoroughly dry mark two straight lines from end to end, a quarter of an inch apart. With a sharp knife scrape off the insulation so that the wires are bare on the outside, but be careful not to disturb the insulation between the wires. To mount the coil, nail at each end a wooden strip three inches wide, three and a half high and one inch thick. This has also to be nailed to the base, and it should be placed so that the coil will clear the base by a half inch. The strip of bare wire on the coil should be uppermost. Now get a brass rod one quarter of an inch square and thirteen inches long; a thin brass strip one quarter inch wide and two inches long; another strip one inch wide and one and one-quarter inches long; and two round headed brass screws. Bend the wider brass strip around the brass rod to form a slider. Bend the narrow brass strip in the center to form a V spring. Solder one end of this to the slider so that it is in the position shown in the drawing. Slip the slider on the brass rod, place the rod in position directly over the pathway of bared wire on the coil so that the lower end of the V spring will press on this pathway, and fasten the rod securely with the brass screws to the wooden end pieces.
Aerial.
Switch.
For the “aËrial” get three or four hundred feet of wire—No. 16 galvanized wire will do, though aluminum or copper wire is better—some insulator knobs, and two cross spreaders three feet long. The parallel wires in the aËrial should be at least two feet apart, and the aËrial should be placed as high as possible so that surrounding buildings, etc., will not interfere with the wireless wave. The bare wires, wherever they are fastened to poles or trees must, of course, be wound around insulators. For a ground connection, fasten an ordinary insulated wire to a water pipe or to a piece of iron pipe sunk five feet in damp ground. A safety switch may be made, like the drawing, from a piece of wood six inches square and an inch thick, a piece of stiff brass three inches long and a half inch wide, and three round-headed brass screws.
Diagram of Circuit.
This completes the separate parts of the receiving apparatus. To connect it up for use, follow the circuit diagram. One wire from the aËrial leads through the safety switch to the tuning coil. From the tuning coil carry an insulated wire to the detector, and from the detector to the ground. The receiver has two wires leading from it—one to a point between the detector and the tuning coil, and the other to a similar point between the detector and the ground. When not in use the aËrial should be connected directly with the ground by means of the safety switch. Where two wires are connected they must of course have the insulation scraped off so that bare wire rests against bare wire.
When you have learned to translate your messages you will be able to do quite a bit of wireless eavesdropping, and your receiver will click with countless messages.
THE END
TRANSCRIBER’S NOTES:
Obvious typographical errors have been corrected.
Inconsistencies in hyphenation have been standardized.
Archaic or alternate spelling that may have been in use at the time of publication has been retained.
