r of surrounding objects as possible. A simple
porcelain cleat at either end, as shown in the drawing, will serve to
insulate it sufficiently.

Your ground connection can be made best by wiring to the cold water
pipe, although wiring to a steam or gas pipe will do almost as well.

You are now prepared to mount the various instruments in their proper
locations. For your table instruments, get a good pine board about
seven-eighths of an inch thick. Buy four binding posts and use one for
the aerial wire, one for the ground wire, and two for the phones or
head set.

To operate the set, first bring the hinged coil of wire close up to
the fixed coil and adjust the detector until you can hear in your
receivers the loudest click caused by the turning on and off of the
key to a nearby electric light. If no light is available, a buzzer and
dry battery should be used. When the detector is properly adjusted you
will be able to hear the buzz quite distinctly in the head phones if
the buzzer is not too far away.

[Illustration: Figure 2]

The actual adjustment of the detector is rather a delicate job, and
once it is in the proper position it is a good plan to avoid jarring
it, as it is liable to get out of adjustment very easily.

Once the sensitive spot on your detector is found, slowly turn the
knob on your condenser and at some spot on it you should be able to
pick up signals of some sort, either of radiophone or spark. If the
set does not work, then go over all your wiring and be sure that the
windings of the two coils are both running the same way.

The above set will work well for short distances, say up to twelve or
fifteen miles. Beyond that, however, it will not receive music unless
you have unusual facilities for putting up an aerial to a considerable
height and well clear of surrounding objects.

Such a set should be constructed at a minimum of cost and may later,
after you have become familiar with the operation of radio appliances,
easily be converted into a set of much greater range by the use of a
vacuum tube as detector and may even, by slight changes, be given the
much desired regenerative effects.

CHAPTER I

A CRY IN THE AIR

"Well, Bob, here we are again. And no word from Jack yet."

"That's right, Frank. But the weather has been bad for sending so
great a distance for days. When these spring storms come to an end the
static will lift and well stand a better chance to hear from him."

"Rig