One of the requisites of a good wireless telegraph detector of the crystal type, is that it be so constructed as to permit easy removal and substitution of different metals for the electrodes, as different metals sometimes produce different results.

Fig. 233 - Details of the construction of the wireless telegraph detector.

The necessary parts of a simple yet very efficient wireless detector are as follows: A base, of the dimensions shown in Fig. 233- 3 inches of 1/2-inch round brass rod; 4 inches of 3/16-inch round brass rod; some brass tubing-, 3/16 inch inside diameter; two thumb nuts of brass or hard rubber, and two binding posts.

The 3/16-inch rod is cut into two equal parts, and both pieces threaded to within 3/8 inch of one end. The other rod is also cut into two equal parts, making a pair of standards. At 1/4 inch from the top of each of the standards a hole is drilled and tapered to receive the smaller rods. The other end of each standard must also be drilled and tapped to receive a machine screw, by which it is fastened to the base. The positions of the standards on the base are indicated on the drawing. The smaller or pressure rods are screwed in the holes on the standards, with the untapped ends facing each other, and the thumb nuts, having previously been tapped to fit the rods, are screwed on them.

The binding posts must now be mounted on the base, and connected to the standards by wires) run underneath the base.

To make the removable electrodes, the brass tubing is cut in 3/8-inch lengths. One-inch disks of 1/16-inch brass, copper, and other metals are cut out, and at the exact center of each is soldered one of the brass tubes, with its length perpendicular to the disk. When it is desired to use them, the tubes are slipped over the ends of the rods, a crystal placed between them, and the rods screwed up so as to hold the crystal in place. Carborur lum and silicon are the most common crystals, although there are many others that produce excellent results.

Fig. 234 - Electrical connections of the wireless telegraph detector.

Fig. 235 - A simple wireless telegraph detector.