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High Frequency Apparatus and Experiments

June, 1917
Page number(s):
117, 154

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 be 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 2½ 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 fine 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 tin-foil, and placing them in a cigar box, to hold them in an upright position. A spark gap of most any type will answer. A 1½ 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.

Fig. 1. Proper Connections for Small “Oudin” High Frequency Coll Excited by a Spark Coil or Step-up A. C. Transformer.

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 are 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 directions.

Fig. 2. Manner of Constructing Small “Oudin” Type High Frequency Coil for Carrying on a Series of Interesting Experiments. One of These Is the Artificial “Aurora Borealis,” Which Is Produced with the Aid of an Incandescent Lamp Bulb, Having Its Tip Portion Coated with Tinfoil, and Connected as Shown.

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 consumption.

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 valuable agent.

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 construction.

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