Further to ChristianJ's calculations, actually radiating 1MW at 19.8kHz is pretty difficult. Antenna efficiencies are going to be low, especially as the highest tower is of the order of 0.025 wavelengths. This means a very low feed impedance and doubtless a high reactance, so the losses in the matching will be pretty enormous. To actually radiate 1MW will probably need something of the order of 50MW of RF out of the transmitter. Not impossible, but you need your own power station!