Counterweight system of the antenna, to replace the ground t. s. f.

摘要

177,869. Eckersley, T. L. Jan. 4, 1921. Aerials.-An aerial, instead of being earthed, is connected to a capacity or screen comprising a number of equal insulated horizontal wires, each wire being of a length at least equal to the height of the aerial above the ground plus the length of the horizontal part of the aerial, if any. The mean distance between one wire and the next is between two and four times the height of the screen above the ground. The breadth of the screen should be at least equal to the breadth of the aerial plus twice the height of the aerial. The height of the screen should be as low as practicable, regard being had to the increase in the number of wires necessitated by a decrease in height. The screen is supported on, but insulated from, metal posts. A nodal point of the system comprising screen and aerial may be earthed. This point may be the point of connection between aerial and screen, or a point on the loading coil. Fig. 5 shows an aerial A and one wire S of the screen. The outer ends of the screen wires may be raised as shown, and the outer wires may be higher than the inner. With an umbrella or radial aerial, the screen wires radiate from a point beneath the centre of the aerial, and the outer ends of the wires may be forked With a fan-shaped aerial of small angle, the screen wires are preferably parallel, or alternatively, as in Fig. 6, in which the outer wires of the screen S are parallel to the outer wires of the aerial A. Unwanted oscillations in the system may be minimized by making the screen wires as nearly equal in length as possibly, and balancing small effective electrical differences of length by inserting induction coils in the wires. A subsidiary screen may also be used below the main screen, the point of connection of the aerial may be adjusted slightly away from a node, or the free ends of the screen wires may be connected.