Fig. 122. Sliders.
Fig. 122 shows two forms of sliders. The first one is the better and to be preferred. A short square brass tube, S, fits snugly upon the square brass rod, R. It cannot turn around but is free to slide back and forth. A strip of spring brass, C, is soldered to the lower face of the square tube. It is bent in a double turn and a punch mark made near the lower end as shown in the illustration. The indentation is made with a center punch, but should not be deep enough to break through the metal.
Fig. 123. Double-slide Tuning Coil Circuits.
The little projection on the under side of C caused by the punch mark is the only part of the slider which should make contact with the wire on the tuning coil. It should slide easily but firmly along the wires and touch only one at a time. Long distance signals will be considerably weakened if the slider touches more than one wire at a time and short-circuits a turn.
Plate IV. Receiving Circuits. (Straightaway Aerial.)
The slider, B, is similar to A except that it has a short length of brass tubing, T, soldered to the under side of S in place of the brass strip, C. A small ball bearing which just fits the bore of the tube is pushed down into contact with the wire by means of a small spiral spring inside of the tube. Both sliders are fitted with a hard rubber handle so that they may be adjusted without the ringers coming into contact with the metal.
Fig. 124. Murdock Double-slide Tuning Coil.