Page:Wireless Telegraphy and Telephony (1908, Massie and Underhill).djvu/34

12. The Antenna

What is probably the most striking characteristic of a shore station is the very tall mast which towers above the operating building. This mast supports a wire, or group of wires, known as the antenna.

The antenna possesses electrical capacity (also inductance), and, therefore, when connected with other apparatus, as in Fig. 7, it disturbs the earth’s magnetic field, as was fully described in Art. 5.

The antenna is connected to the inductance through one of the flexible connections, as shown in Fig. 7. The length of the antenna varies according to conditions, the supporting mast in some cases being nearly 200 feet high, and in at least one case the height is 418 feet. The antenna is sometimes attached to captive baloons or to kites, and suspended in this manner for temporary service, as in military operations. On boats the antenna is attached to the masts.

13. Tuning the Transmitting Apparatus

As explained in Art. 5, it is necessary to have the oscillations of the Leyden jars in synchronism with the antenna circuit. The adjustment is made on the inductance coil as shown in Fig. 7. It can be readily seen that the Leyden jars and antenna circuits can be adjusted independently of one another, but always having more or less