Fig. 11. Murdock Receiving Set.
Fig. 11 illustrates a receiving set manufactured by the Wm. J. Murdock Company. The tuning coil is fitted with hard rubber composition ends and is wound on a special core which is not affected by temperature changes. The detector is of the crystal type and is of rather unique construction, since the small fixed condenser is mounted in the base of the detector itself.
The Clapp-Eastham set in Fig. 12 employs a receiving transformer which makes great selectivity possible. The detector is mounted at the left-hand side of the outfit. A very sensitive mineral called "Ferron" is used in the detector. The fixed condenser is enclosed in a brass tube fitted with hard rubber ends and is located on the front of the base, directly in the center. A variable condenser of the rotary type is placed at the right-hand corner.
Fig. 12. Clapp-Eastham Receiving Set.
The Prague Electric Company manufacture the apparatus shown in Fig. 13. The cabinet is mahogany and is fitted with a hard rubber cover. A fixed condenser and a double slide tuning coil are mounted within the cabinet. The sliders of the tuning coil project through two long slots in the cabinet. A universal detector mounted on top of the cabinet is so designed that any material may be experimented with or tested.
Fig. 13. Prague Receiving Set.
Fig. 14 shows a receiving set built up from apparatus described in this book. The cabinet is 12 x 16 inches and 4 inches deep. The wood should be 1/2 inch thick, and in order to present a good appearance is preferably of mahogany. As mahogany is sometimes very hard to procure and expensive, some may find red birch an excellent substitute. When stained with a mahogany stain it presents a fine appearance.
