Directive radio transmission on a wavelength of 10 meters

Directive radio transmission on a wavelength of 10 meters

Author: Dunmore, F.W. Engel, F.H.

Year: 1923

Reference is made to Marconi's recent work on short wave-length transmission and the advantages of short waves for directive work. The authors have experimented on a 10-m. wave-length using at the transmitting end a parabolic cylindrical reflector. The apparatus is described in great detail, with dimensions to enable other investigators to continue the experiments. The transmitter was a 50-watt tube of the coated filament type, inductively coupled to a balanced aerial and counterpoise. This was placed at the focus of a grid parabolic reflector (see diagram), each wire of which was tuned to 10 metres. The focal distance was 1/4 of the wave-length. The radiative properties of this reflector are discussed in detail. The receiving apparatus was a 3-valve instrument coupled to a frame aerial capable of orientation, and intensities of signals were quantitatively recorded by means of a thermocouple. The results obtained, under various conditions with fixed receiver and rotated transmitter, are shown by polar diagrams. These demonstrate the effect of detuning and tuning each wire of the reflector, effect of increasing the reflector aperture, effect of removing alternate wires, and effect o