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