So, at 52 MHz, the field strength drops to zero at 5 km. Well, not transmitting any energy very far like that.
And, at 1.82 MHz, they get signal out to 30,000 km! Hmmm, where the hell did they find a 30,000 MILE long radio test range? The entire circumference of the earth is is 25,000 mi, but their last data point is OVER 30K! (Or, maybe I'm confused by the different dots on the chart.)
And, of course, the FCC and other nation's agencies might have something to say about broadcasting energy this way.
Jon