<i>Alternatively, could this be an unpowered antenna that is picking up signal from a nearby powered one? </i><p>I&#x27;m pretty sure this is what&#x27;s happening.  From past experience with high voltage arcs (admittedly at 60hz, not ~1 MHz), I don&#x27;t think we&#x27;re seeing more than a few hundred watts of power in that arc.  Also, if this tower was actually the one transmitting that signal (presumably 50kW is the transmitter power) they&#x27;d shut it off or switch to a different antenna for maintenance on this one.  If you shorted the output of the transmitter at the point where it&#x27;s normally driving a resonant load, the best possible case is that it would trigger some kind of automatic shutdown on the final amplifier.