You'll be much better off simply using the conventional radio approach than trying to simulate everything, especially when circuit equivalents are nebulous like this.
After all, if you can't quite tell what it *should* look like, how would you know if you could implement your model once you've found a satisfactory result?
What kind of antenna are you looking at, loop? The first thing to know about a loop is, if it's a very small loop (I'm guessing, at this frequency, it is), its radiation resistance is very low, meaning, you can treat it as a nearly pure inductance (Q > 10 I think is typical), and its bandwidth (even with a matched load) will be correspondingly narrow.
The nature of the incoming signal could be modeled as a voltage or current source; how doesn't really matter, because it isn't really either, it's a power source that couples in. Again, you don't have voltage without current and vice versa, it's all about power flow, and the matching that allows the power to flow.
Since the loop is inductive, your first priority is to resonate it with a capacitor at the desired frequency. This will require a very precise value, and even for a single frequency, may require a variable capacitor to account for manufacturing tolerances. In the AM BCB, a Q of 10 gets you 50-160kHz bandwidth, so you only get a few channels for any given tuning position. And if the Q is higher, you get even fewer.
Now that you've got a high Q resonant tank, you can do two things: couple into the voltage across the capacitor, or the current through the inductor. You need only a small fraction of either, because the Q is still going to be large. This can be arranged with a voltage divider (usually the capacitor is split into a huge hunk and a small variable part, e.g., 300pF variable + 10nF, output from across the 10nF), a transformer (a potential transformer across the cap, or a current transformer in series with the inductor), an inductive pickup (the big loop carries lots of volts, but you only need a few, so a much smaller loop can be placed inside the big loop), an impractically large inductor (like in my example circuit, which models radiation resistance as a parallel equivalent), etc. Whatever the case, you need to match transmission line impedance (e.g., 50 ohms) to radiation resistance (whichever series or parallel equivalent you have).
Once you get the signal into a transmission line, with a reasonable match (Z ~= Z_line, or alternately, SWR ~= 1), you can do whatever you want with it. Put it into an amplifier (don't forget to match it, too), etc. Yes, you're going to have funny behavior at other frequencies, and if you're concerned about those frequencies, you'll have to choose the coupling circuit and adjustable (or selectable) components accordingly. But for the most part, you completely ignore any frequency that you aren't tuning for, usually enforcing that concept by inserting filters to reject any stragglers.
Example: suppose you have a loop of 5uH and need to tune it to 500kHz. It has a reactance of 15.7 ohms. Suppose further it has Q = 20. The ESR (not counting DCR and skin effect) is X_L / Q, or 0.78 ohms; alternately, the EPR is X_L * Q, or 314 ohms. The capacitor required is 20.3nF. If we use a current transformer to match to a 50 ohm line, it needs an impedance ratio of 1:64, or a turns ratio of 1:8. If we use a voltage transformer, it's of course 8:1. (A capacitor divider is unsuitable for resonant impedances less than line impedance, since it can only divide the impedance down. If the inductance were a lot larger, it could be used.) To a rough approximation, a smaller inductive loop, of 1/8 diameter of the larger, I think, would also work.
Tim