Wireless Telegraphy and Telephony Simply Explained / A Practical Treatise Embracing Complete and Detailed Explanations of the Theory and Practice of Modern Radio Apparatus and Its Present Day Applications, Together With a Chapter on the Possibilities of Its Future Development

by Alfred Powell Morgan

The wires leading from the aerial to the operating room are called the "rat-tail," or "lead-in." They must be very carefully insulated by leading through a bushing placed in the wall or window of the operating room.

One of the most important factors in a wireless station is the proper earthing arrangement. The usual method is to use large copper plates buried in moist earth, or thrown in the sea. On shipboard it is merely necessary to connect the earth wire to the metallic plates of which the hull of the vessel is built. Amateurs employ the water or gas pipes in the house, the former being preferred. Connections are established by means of a ground clamp.

In the country, where water-pipes are not available, the best way is to bury a sheet of copper three or four feet deep in moist earth.

A very efficient earth can be formed by spreading a large area of chicken wire netting over the ground. This method is the best where the earth is very dry or sandy, and no other way is readily convenient.

FIG. 27.—A side view of the aerial shown in Fig. 22.

CHAPTER III. THE TRANSMITTING APPARATUS.

The principal instruments composing the apparatus used for sending the wireless messages comprise an induction coil, or in its place a transformer, a key, a spark gap, a condenser, and a helix.

The current supply available will determine the type of the instruments, and whether an induction coil or a transformer is used. Unless current mains for light and power are already installed, it must be generated by an engine and dynamo, or recourse had to batteries. Induction coils may be operated on either direct or alternating current. Dry cells are most commonly employed to furnish the current for small induction coils, but a storage or some form of renewable primary cell, such as the Fuller and Edison, is necessary if the coil is a large one. When dry cells are used, they should be connected in series multiple, as shown in the accompanying diagram. This method of connecting distributes the load, and considerably lengthens the life of the battery.