The Radio Boys on the Mexican Border | Page 2

boy interested in radio telephony may construct his
own receiving set, the Author herein will describe the construction of a
small, cheap set which almost any lad handy at mechanics can build.
Such a set should be sufficiently powerful to permit of successfully
picking up the concerts and other programme entertainments being
broadcasted frequently by stations throughout the country.
Two drawings are given herewith which will enable boys to visualize

the appearance of the set, and will be of aid in following instructions.
Referring to Figure 1 let us examine first the construction of the
receiving inductance marked L. 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. If you are handy with tools, however, you can
buy the galena and make your own detector. It will work with more or
less satisfaction.
Your next need will be the condenser. The condenser consists of a
series of aluminum plates, some of which are movable and the rest
stationary.

Buy a small variable condenser. Its function is to tune the secondary
circuit, which is accomplished simply by turning the knob. Such a
condenser could not be made without the use of a good set of tools, and
the author strongly advises it be bought instead of made at home in
order to avoid trouble. The aluminum plates are spaced very closely
and great care should be taken to avoid bending them, as they must not
touch each other.
The aerial for this set should be about 60 to 100 feet in length and as
high and clear 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