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Loop Antenna at ~60 kHz
I have a project in mind that would need a very good antenna in the
frequency range of 60 kHz. Originally I looked at loop antennas and liked the idea of a large shielded loop made of coax tuned with a capacitor. My goal is to get as large a signal as possible from the antenna and matching circuit to allow the use of a receiver with very low sensitivity... in fact an all digital receiver. I spent some time simulating antennas in spice and was able to get a bit of a feel for the circuit, but I'm not convinced it would work the way I want. Just before I set the project aside I was told I needed to model the radiation resistance. That has the potential of wrecking the Q of the circuit. I am counting on the high Q to boost the output voltage. If the radiation resistance is at all appreciable I would lose the high Q and need to start over. Anyone have an idea of how to estimate the radiation resistance of a tuned, shielded loop antenna? The other factor I don't understand how to factor in is the distributed capacitance of the coax. Is that a significant influence on an antenna or is it in the noise compared to the tuning capacitor. The coax is RG-6-Solid Coax Cable. The loop is made up from 50 feet of this. The specs are 16.2 pf/foot and 6.5 mOhms/foot in the center conductor, or would the resistance be a round trip measurement of both inner conductor and shield? I assume the shield has a much lower resistance than the inner conductor but I don't know that for sure. -- Rick |
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