But this is New York City. The AM pirate may be entirely within one apartment, and the building's electrical system may be acting as the antenna. With FM, the antenna has to be outside and high for good coverage, but an AM antenna can be hidden. The nearby buildings will also reradiate the AM signal, so the direction finder will point towards every building. With FM multipath, the direction finder would point towards the reflector of the signal, but once you get to that place that's reflecting the signal, it would point to the source. But AM signals are reradiated for a long distance due to the higher wavelength. That's why AM stations have to plan for other towers within a mile because those reradiate the signal and mess up the directional pattern.