Standing Electric Waves on Parallel Wires

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Abstract
Measurement of short electric wave-length with a parallel wire receiving system.—Electromagnetic waves of from one to ten meters in length and highly constant in nature were obtained by means of a valve oscillator. Two types of generating circuits are described. Analysis of the possible free modes of electric vibration of the parallel wire receiving system indicates that for normal coupling with the valve generator there are always to be found two sets of current maxima. When the sliding bridge is at a position indicating maximum current flowing through the thermo-junction, standing waves exist in a section of the parallel wires included between the bridge and one or other end of the wire system. A change in the terminal conditions at either end of the parallel wires changes the position of the set of resonance points formed by reflection of waves from that end, but does not alter the location of current maxima which are determined by standing waves reflected from the other end. The half wave-length is equal to the distance between successive positions of the bridge at resonance in each of the two sets. Measurements obtained were constant to one part in one thousand for readings requiring a total time of only from two to four minutes. The measured wave-length is independent of mutual effects of exciter and receiver. It is not altered by a change in the diameter or spacing of the receiving wires, or by a change in the material, provided it is non-magnetic.

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