High Frequency Apparatus and Experiments
By Hubert A. McIlvaim
MANY experimenters either do not realize the vastness of the high
frequency field, or think that they have not money enough to buy
the necessary apparatus. It is the purpose of this article to
explain the manner of constructing a few simple instruments, and
the method of carrying out some simple experiments.
In the first place, a high frequency transformer must he
constructed. An Oudin coil will be the best for all-around work,
and it may be made in the following simple manner: Procure an
ordinary pasteboard mailing tube, about 2 1/2 inches in diameter
and 10 inches long, and cover it with a thin coat of white shellac.
While this is still wet, wind the tube with line copper wire,
spacing the turns far enough apart to ensure proper insulation.
(Enough wire may be found in an old telephone ringing magnet.) Glue
this tube upright to a base and fasten three posts on the base. The
primary coil may be made of 6 turns of No. 14 copper wire,
connected as in the diagram, Fig. 1.
A condenser can be made by coating both sides of old photographic
plates with tinfoil, and placing them in a cigar box, to hold them
in an upright position. A spark gap of most any type will answer. A
1 1/2 inch spark coil should be used.
When the above instruments are constructed, they should be
connected up as shown in diagram, and the apparatus is ready. When
the spark coil is operated, a brush discharge of purple light
should appear around the free end of the secondary, upper end of
coil, with sparks about 2 or 3 inches in length. If a piece of
metal is held in the hand, a very long spark can be drawn from the
secondary wire, without the slightest shock. If, however, the spark
is drawn directly into the hand, a severe sting may result. On the
other hand, if a pane of glass is held between the secondary wire
and the hand, a spark may be received directly into the hand
without pain; the spark, being dispersed or spread out while
passing over the glass.
If a person insulated from the ground grasps the free terminal of
the secondary, a match may be lighted from any part of the body. A
Geissler tube will light up brightly, when brought near the body.
This is also a good way in which to treat heart and nervous
diseases. If there is any local trouble, a grounded metallic object
should be brought near the point to be treated, thus taking out the
induced current at this point.
An interesting experiment is to produce an artificial Aurora
Borealis. This may be accomplished with a large electric bulb (a
100 watt, burned out one will do), covering the tip with tin-foil.
Insulate the bulb from the ground and fasten the screw end to the
secondary wire. Place a strong permanent magnet on each side and
start the coil. A beautiful auroral effect will form inside the
bulb. Also, if there arc any loose pieces of filament, these will
begin to revolve rapidly about the inside of the bulb and will
continue to do so for some time after the current is shut off, and
each time they touch the glass a shower of sparks will Fly in all
A by-product of high tension electrical stress in the air is ozone.
Ozone is merely electrified oxygen. When a high voltage discharge
takes place in air or pure oxygen gas, the atoms of oxygen are
"torn apart" and exist in what is known as a nascent state. In this
state each atom combines with one other atom, and the chemical
affinity of these two atoms is such that, as there is nothing with
which they can combine, these atoms pull to themselves and combine
with a third atom of oxygen. Thus it is that a new gas is formed.
This gas is much denser than oxygen and is many times as active.
The smell of ozone is very strong and there seems to be a slight
difference in the smell of ozone produced with a static machine and
the ozone produced with high frequency current. Ozone is an
excellent "germ killer." as it kills all kinds of disease germs on
contact. If it is administered properly, and in time, it will cure
The electric stress about the coil is so great, that immense
quantities of ozone are constantly being generated. In order to
treat diseases obtain a box which is large enough to contain the
coil and still leave enough space (about 4 inches) on each side to
prevent the coil from "grounding." Run the coil wires through the
box and leave the free end of the secondary about six inches long,
so as to obtain good radiation surface. Place a hose in the top of
the box and another in the lower part of one side. Paraffin the box
to prevent leakage, and put a small window in one side so that the
coil action may be viewed. Either air or pure oxygen is taken in
thru the lower hose and the ozone is inhaled, or otherwise applied
from the upper hose. In fumigation, treatment of coughs, pneumonia,
colds, and for many other medical uses, besides oxidation of
certain materials, bleaching flour and cloth, experimenting with
its use in welding and many other commercial uses, ozone is a most
Taking the high frequency field as a whole, it is well worth while
for more experimenters to work with it. High frequency current has
the properties of both static and galvanic electricity, besides
many properties which neither of the above possess. It will pass
over ordinary insulators, such as glass, almost as easily as low
frequency current will pass thru copper. It travels over the
surface of a conductor and seldom thru it. Its oscillations are so
rapid that it will not produce an audible sound in the receivers,
so that the discharge of an Oudin coil cannot be used for the
transmission of wireless messages, altho who can say, if it is
properly conducted to the aerial, that it does not travel as far or
farther, than an undamped wave.
It is very probable that high frequency current of a periodicity
which is not detected by the senses, will play an important part in
radio thought transmission.
If experimenters will build apparatus, similar to that described,
they will never regret the little amount of time required for its
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