It is suggested that the amateur experimenter not confine his work to receiving only with a single type of detector but rather accustom himself to the different instruments.
During the past few years many wireless telegraph detectors have been invented which lend themselves readily to amateur construction. It is somewhat of a convenience to have a "universal" detector which with a little manipulation may be used as more than one type and thus save unnecessary expense and much labor.
The "universal" detector shown in Fig. 88 has been so designed as to present a good appearance and at the same time be successfully operated as an electrolytic, tantalum, peroxide of lead, silicon, carborundum or any of the crystal type detectors.
Fig. 88. Universal Detector.
Fig. 89. Details of Universal Detector.
The standard, R, is a 3/4-inch hard rubber rod, 1 1/4 inches long, with a 3/16 inch hole bored through its axis. A spring, S, is made after the plan shown in Fig. 86. It is 2 inches long and 1/16 inch thick. A brass collar 1/8 inch thick and 3/8 inch diameter is soldered on the smaller end of the spring in order to so reenforce it that it may be bored and threaded with an 8-32 tap to receive a thumbscrew. The brass standard, D, is a small cylinder 3/8 inch high and 1/2 inch in diameter. A 3/16 inch hole is bored through its axis. The arm, A, is brass and measures 1 1/2 x 1/2 x 1/4 inches. The ends are rounded by filing or grinding so that they coincide with the semi-circumference of a circle having a diameter of 1/2 inch. Two holes are bored on the center line 1/4 inch from each end.
One is a 1/8-inch hole and the other is threaded with a 10-32 tap to fit the large adjusting screw. The adjusting screw, H, is 1 1/4 inches long and has a 10-32 thread. A hard rubber head 1 inch thick and 1 1/4 inches in diameter is clamped to the upper end by means of two hexagonal brass nuts. A small brass washer should be placed between the head and each of the nuts to give it a more finished appearance and prevent the nuts from marring the rubber.
