This is an interesting, but older document dealing with stations going down to a couple of Hertz. The lower the frequency, the larger the antenna and therefore

This is an interesting, but older document dealing with stations going down to a couple of Hertz. The lower the frequency, the larger the antenna and therefore the station needs to be. Currently probably the HAARP station[1] in Alaska would qualify as the largest radio station. It goes down into the 0.1 Hz range. From my limited understanding it is only possible to do so, because it basically utilizes the athmosphere itself as antenna. [1] https://en.m.wikipedia.org/wiki/High-frequency_Active_Auroral_Research_Program https://en.m.wikipedia.org/wiki/High-frequency_Active_Aurora...