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This paper considers a number of problems which have been encountered and solved in the design and construction of an experimental millimeter-wave amplifier using a microscopic helix only 0.015" in diameter. Amplifications of as much as 19 db have been obtained at a wavelength of 6 millimeters, and amplifications of 9 db have been measured at wavelengths as short as 5.2 millimeters.
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Sloan D. Robertson (1954) studied this question.
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