Polarization and Multipath, page 2

CHRONOLOGY OF POLARIZATION RESEARCH

A brief survey of the literature begins not with radio but with the 1943 proceedings of the National Television System Committee. The Committee considered scores of reports dating from the early 1900s and found quite important a research study performed by R W. George in New York City that demonstrated that in both the 81-86 MHz and 140-145 MHz bands, reflections were 60 percent higher for vertical polarization. Other studies showed the ratio of maximum to minimum field strength had been observed as follows:

Horizontal Ratio Vertical Ratio
176-182MHz

81-86MHz

140-145MHz

1.32

1.89

1.86

2.97

2.12

3.38

However, the Report found vertical polarization superior in ability to minimize fading and variations in field strength and in making best use of efficient receive antennas. Neither polarization was found superior in terms of basic propagation prowess. Horizontal was given the nod not only for minimal multipath reflections, but also for superior immunity to noise, and a more efficient transmitting antenna. Overall, the committee substantially agreed that horizontal had the edge, despite two sharply divided camps at the beginning of the deliberations. The "displacing of images" that could appear due to multipath signals appeared to be a dispositive factor in the adoption of horizontal polarization for television in America.

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