On the Wireless Beam of Short Electric Waves. (VI)

Abstract

A new method of direction control of the short wave beam is described, and the experimental results are given in the paper.
The arrangement of the system for the case with eight directionality is shown in the following figure.
A vertical sending antenna denoted by O is at the centre, and of 16 other conductors erected around it, R's are reflectors and D's are directors. They are arranged on concentric circles whose radii are 1/4λ and 1/2λ(λ being the wave length) respectively.
Maximum energy is radiated in the direction of the arrow. When the length of D's is varied, the radiation in the arrow direction changes, and so long as the length is larger than 1/2λ, the wave is almost screened and comparatively little energy is transmitted.
On the other hand, when their length is made smaller than 1/2λ, there is a region in which the received energy becomes much augmented due to the existence of the rods.
If means are provided to control the natural wave-lengths of rods, so that the wave may be radiated in any other desired direction, then the beam with variable directionality can be produced. Thus the wave may be sent into several different directions in any desired order or especially in successively rotating manner. The control of rods may be done electrically or mecanically, by push button device or by automatic means, and the beam can thus be roted neither by changing the position of conductors nor by revolving a large structure.
Another case for 16 different directions has also been experimented, and the polar curve is given.
More wave directors may conveniently be arranged along radial lines to improve the sharpness of beam in those directions. The interval between these directors must of course be larger than 1/4λ and smaller than 1/2λ.
This sort of short wave radio beacon is quite simple and is belived to find applications in directing ships approaching the shore or guiding the aviators flying in the darkness.