300 Mw ?
The biggest AM station was 1 Million Watts (1 megawatt).

UHF TV stations are licensed up to about 3 Megawatts, but this is "beamed" by
concentrating the signal along the horizon. The actual transmitter is 100 KW or
so.

Shortwave broadcast stations have transmitters up to about 500 kW but antenna
gains of 20 dB or more can make it seem like several million watts if you're in
the target area.

But let's assume that since Mindanao has mostly AM receivers that the the 300
megawatt transmitter is non directional (no antenna gain), then it would need
to draw about 400 to 500 Megawatts of power from the power grid.
Enough to power a major city or two.
Will they be erecting two or three new nuclear power plants nearby to power it?

At 5 Billion dollars each, this seems very wasteful of scarce resources. So
it's a 10-15 Billion dollar project.

SOMEBODY must a have a really important message