Well it amplifies the signal by the Q of the antenna. The issue is that high Q resonators make lousy radiators, as the radiation resistance is very low compare

Well it amplifies the signal by the Q of the antenna. The issue is that high Q resonators make lousy radiators, as the radiation resistance is very low compared to the reactance, and bandwidth is 1/Q. But you can certainly get amplification by a high-Q resonator inserted in a field. This is why electrically small antennas have an effective aperature much, much larger than their physical size. That ferrite rod antenna in an AM radio can have a massive electrical aperature (antenna gain) since it is narrow band (high Q). The resonance is amplifying the signal. You can also transmit through it if you can keep it cool. It may have 0.1% efficiency, radiating 1W for 1 kW of input power, if you have a nuclear reactor (say a VLF antenna on an aircraft carrier where you can’t have wire antennas), you can trade power for size.