Stress-Induced Noise in Magnetic-Cored H-Field Antennas

Abstract

Work is being conducted at the Naval Underwater Systems Center in the design and development of low-noise, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</tex> -field antennas for incorporation in submarine antenna systems consisting of towed, horizontal, electric dipole <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -field antennas. Utilization of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -field and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</tex> -field antennas in a common cable will permit omnidirectional extremely low frequency (ELF) reception by a submarine. This paper discusses various experiments that have been conducted to determine the effects of magnetic core geometry on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</tex> -field antenna SNR for the case where stress-induced core noise is the dominant antenna noise. A substantial improvement in the SNR is realized by cold-working the antenna core into a helically wrapped structure. The mechanical strain relief, or insensitivity to tensional stresses achieved, gives the helical structure a definite advantage over the axial design.