Just remember the frequency.
The lower you go, the closer it gets to longwave.
The groundwave is superior to the skywave at lower frequencies. A small power increase at 648kHz is more effective than it would be at the top end of Medium Wave.
The power increase here in Lincolnshire, almost totally flattened the skywave content that was causing distortion after dark.
Plus the stations that share the channel were also flattened.
This has to be taken into account when doing comparisons. Especially on a vertically polarised transmission, which is actually meant to favour groundwave as opposed to DX after dark.
It obviously does not stop it, but it has a great effect.
Bear in mind that DX after dark is mostly Horizontal, as the RF gets twisted on reflection.
David (G1ZQC).