Low-Profile VHF Antennas for Seismic Detection Systems.
HARRY DIAMOND LABS WASHINGTON D C
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The paper describes the design, fabrication, and evaluation of three different types of low-profile VHF antennas and their applications with seismic detection systems at or near ground level. These electrically small antennas vertically polarized include a capacitively tuned multi-turn loop over a small metal ground plane, a spiral transmission line top-loaded monopole, and a capacitor-plate antenna that can be inductively tuned over a wide frequency range. The radiation pattern of each is essentially that of a dipole, omnidirectional in the horizontal plane and represented by a solid of revolution generated by a rotating figure of 8. All of the above elemental dipole antennas were designed for optimum performance in the 100- to 200MHz frequency range, compatible with various physical, electrical, and environmental constraints determined by the terminal delivery vehicle TDV of the seismic detector system. Distinctive features of these low-profile antennas include small size 3 in. maximum, simplicity of construction, and low fabrication costs. Author
- Electrical and Electronic Equipment
- Seismic Detection and Detectors