Woroncow, Aleksander (1977) Development of active loop antennas for 2-30 MHz. University of Southampton, Doctoral Thesis.
Abstract
Active antennas using a single balanced loop, and ar omnidirectional crossed loop arrangement have been constructed, up to 160 cm diameter, for reception in the frequency band 2-30 MHz. Their performance has been investigated theoretically and experimentally. 160 cm active loop antennas are atmospheric noise limited for approximately 75% of time, according to C.C.I.R. noise data. Under conditions of minimum atmospheric noise (less than 25% of time) their performance is short by 7-11 dB of that ideal goal, and so, for that matter is a 160 cm active monopole. Linear amplifiers using bipolar transistors, accommodating signals up to 5,V/m, have been developed; there is the possibility of increasing this figure up to 10 or 1S V/m. Noise in transistors has been investigated and this has led to the development of amplifiers with improved signal to noise ratio for active antennas. Performance of active loop antennas has been compared theoretically and experimentally with that of active monopoles, and it has been shown that approximately equal signal to noise ratio is obtained for either of these electromagnetic sensors when their overall dimensions (diameter and height) are similar.
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