. Practical wireless telegraphy; a complete text book for students of radio communication . current are notuniformly distributed in vertical aerials, a very much greater potential exists atthe top than at the base. This non-uniform distribution exists to some extent inall types of aerials, but is less manifest in the flat top aerials than in vertical any conductors at the top or the free end of the aerial that would tend tostart leakage of the high voltage current should be widely separated and thor-oughly insulated from the aerial wires. lis. Various Types of Aerials.—Four general
. Practical wireless telegraphy; a complete text book for students of radio communication . current are notuniformly distributed in vertical aerials, a very much greater potential exists atthe top than at the base. This non-uniform distribution exists to some extent inall types of aerials, but is less manifest in the flat top aerials than in vertical any conductors at the top or the free end of the aerial that would tend tostart leakage of the high voltage current should be widely separated and thor-oughly insulated from the aerial wires. lis. Various Types of Aerials.—Four general types of aerials are in use: (1) The vertical or fan aerial; (2) The umbrella aerial; (3). The inverted L flat top aerial; (4) The T aerial. (a). The vertical aerial shown in Fig. 139 consists of a fan or harp of copper or silicon bronze wires held vertically into space by a wooden mast, a steel tower or any convenient structure of sufficient height. The wires of the harp may or may not be joined at the top. All wires, however, must converge at the lower end AERIALS OR ANTENNAE. 119. Fig. 141—Inverted Flat Top Aerial. where they enter the station house and are connected to the apparatus. The freeend of the vertical aerial must be well insulated to prevent direct leakage to thesupporting hal)ards or stays, and at the lower end the wires must be stayed totake the strain off the station house roof insulator. Although the ver-tical aerial is ac-knowledged to bethe best radiatorof electromagneticwaves practicallyequal results can beobtained from a flattop aerial (ofincreased d i m e n -sions) with a lessexpensive supportingstructure. Irrespec-tive of the degree ofefficiency obtained, a vertical aerial could not possibly be used aboard vessels onaccount of the derrick booms, mast guys and smoke funnels which take up thespace that would be required for erection. (b). The umbrella aerial shown in Fig. 140 receives its name from its generalshape and similarity to an umbrella. It wi
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
