When running high power AM, (and short antennas) you have to be ready to expect the unexpected. getting all of the bugs worked out is the challenge and half of the fun...........
I worked for a Mexican radio network back in the 70s, and had to rebuild a vertical antenna matching unit in Oxaca.
If I remember, it operated around 800 kHz and the tower was only some 80' high, pushed by a 5kW transmitter. A real 'shorty', close to the flight path at the local airport.
The whole damn thing glowed blue at night & pulsed with modulation, too cool.
It was the only time I had to use the 'extended range' on my operating impedance bridge to do a base measurement. It read some ridiculously low resistance, and the -J was in the thousands of ohms.
Not efficient, but it was the best they could do on the dirt available.
The ATU had been whacked by lightning, and was a total loss.
73DG