The latter is shown in detail in Figure
2, and consists of a heavy piece of cardboard. The back of an ordinary
writing pad will do.
[Illustration: Figure 1]
First, draw the circle out with a compass to the diameter shown and
then divide off the outside into an unequal number of divisions as
shown. Draw a light pencil line through each of these marks to the
centre of the circle. Now with your scissors cut out the disc, after
which you cut the slots as shown.
The slots should be about one-quarter of an inch in width and of the
depth shown in the drawing. Two such discs should be made and, when
all cut out, should be given several coats of shellac to add stiffness
and to improve the insulating qualities.
Now at your hardware dealer's buy one-quarter pound of No. 24 double,
cotton-covered wire and proceed to wind the coils in the manner shown.
Keep the windings even and avoid all joints throughout the length of
winding.
When you have finished, mount the coils as shown in the drawing. Make
sure that the windings on both coils run in the same direction. If you
fail to do this, the set will not work.
For the detector, it is better to purchase a good make of galena
detector at any radio supply store.
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