I was digging around trying to find some software to help me design a magnetic loop antenna for use on VLF frequencies. I stumbled across this page, which provided a lot of interesting insights, as well as a Spice model to help you understand how they work.
The article clarified something to me which I only vaguely understood before. If you desire narrow band performance, the best way to do it is to make the antenna resonant by paralleling it with a capacitor, and using it in combination with a high impedance load to measure the voltage from the antenna. But if you desire wide band performance, then you want to use it combination with a very low impedance, which basically means that you feed it into a transimpedance amplifier which effectively shorts the antenna to ground and converts the current to a voltage.
I might have missed it, but while the page presents an Spice model for the antenna, it doesn’t seem to have it available for download. I’m working on putting it into LTSpice, and should have it available for download sometime in the next couple of days.