OCR Text |
Show Crystal Detector May Be Easily Constructed Experimenters are constantly bringing bring-ing out new designs for crystal detectors. de-tectors. A fine adjustment can be made on any point of the crystal with the one here described. It Is mounted on a wood base, 6 by 3 by Inches. The materials required re-quired are a base, two binding posts, a strip of spring brass by inches, a wooden pot-lid knob, three small lock washers, and several pieces from a structural toy set such as "Erector" or "Meccano." To make the universal joint first get a 2-Inch strip, three small angle pieces, and several nuts and bolts from the toy set. These are assembled as shown In the diagram with lock washers wash-ers under the nuts at the points B and 0. A round-head wood screw with a lock washer under the head is used to hold the joint to the base at A. A plain washer Is placed between the wood and the angle piece to make It turn easily. The knob Is put on one end of the horizontal arm and the cat-whisker cat-whisker on the other. A wire Is soldered sol-dered near the middle of the arm and a pig-tall lead Is made over to one binding post. The screws at points A, B ' and 0 should be adjusted to give the desired de-sired stiffness of operation. The crystal holder is shaped from the strip of spring brass. This is bent hairpin shaped as shown and an angle piece is soldered on one side. A wood screw Is used to fasten it solidly to the base. This holder is connected to the other binding post. The holder should be made so that It closes all the way when the crystal is not In It. If lock washers are not to be had, small stiff springs can be used in their place. |