The submarine-towed ELF loop antenna

To obtain omnidirectional reception, a solenoidal loop antenna can be built into the same cable as that used for the ELF electrode-pair antenna. The loop's noise voltage is higher in level and is more complex than that of the electrode-pair antenna. Measurements of towed cable vibration, of towed antenna noise, and of the physical and electrical properties of antenna cable samples have been made to clarify the noise production process. The results have included (i) the development of a quantitative theory for each significant noise type, (ii) the identification of a number of noise suppression techniques, (iii) the realization of a low noise level, in agreement with theoretical predictions, when an antenna incorporating some of these techniques was tested at sea, and (iv) the construction of various laboratory facilities for testing candidate antenna designs, the most notable being an antenna-towing simulator in the form of a shielded water-flow tunnel.