Wireless Telegraph Construction For Amateurs

by Alfred Powell Morgan

Fig. 43. Electrolytic Interrupter.

The lower end is fitted with a spark plug porcelain. The porcelain must fit the tube tightly and not leak. The electrode, P, is a piece of brass wire which will just pass through the hole in the porcelain. The upper end of the electrode, P, is soldered or fastened otherwise to the lower end of the rod, A.

A small hole, h, should be made in the tubes, N and V, above the level of the electrolyte in the jar. When the interrupter is in operation the electrolyte gradually rises in the tubes, and would corrode the lower end of A if it were not able to pass out through the vents.

In the Simon-Caldwell interrupter, a strip of lead passes from the binding post mounted on the foot of the yoke down inside of the test tube. The size of the hole in the tube is regulated by revolving the fiber head so that the glass pointed rod will be inserted in or withdrawn from the hole.

The frequency of the interruption will also depend somewhat on the concentration of the acid solution. It is therefore best to start with a weak solution and add acid slowly until it is of the proper strength.

CHAPTER VI. TRANSFORMERS.

Where alternating current is available in commercial wireless telegraph stations, the induction coil has been gradually superseded by the more modern transformer for charging the oscillation condenser. Since the transformer is less expensive to construct than an induction coil capable of transmitting the same distance, it is favored by many amateur experimenters. A one quarter kilowatt transformer has a sending range of over 50 miles when used with a properly constructed aerial about 80 feet high. This is probably the size best suited to the average private installation.

The secondary of a wireless transformer seldom develops potentials exceeding 15,000 to 20,000 volts, while those of an induction coil range from 1 5,000 to 300,000 volts. However, the strength of the secondary current of a transformer is so much greater than that of an induction coil, that more powerful and penetrating waves are developed. For these reasons a transformer is always rated by its output in watts or kilowatts rather than by the spark length produced at the secondary terminals. The spark of a one quarter kilowatt transformer is only 0.25 to 0.50 of an inch, while the spark of a one half kilowatt transformer may be the same length but still represent more energy.

There are two distinct types of transformers in use, known as the "open" and "closed," accordingly whether the core is straight like the core of an induction coil or in the form of a hollow rectangle. The open core type is used in the government stations and by the United Wireless Telegraph Co. It is the simpler and more easily constructed of the two, but is also less efficient and requires that more material be expended to bring it up to a definite rating. In principle it is simply an induction coil operated on alternating current minus the interrupter and condenser. In view of the greater currents employed, the windings must be larger and heavier than those of the induction coil to prevent heating.