I have a local MW station (630 WMAL) that is radiating harmonics (1260,
1.890, etc.) on up the spectrum.

The harmonics are strong enough that 1260 AM (also a local station) is
unlistenable for about a mile surrounding WMAL's towers. It's also an
irritation throughout the SW bands.

I am rather certain that the harmonics are coming out of the
transmitter and not the result of local rectification (near or in the
receiver) because building a trap for 630kHz has no effect on the
harmonic and the harmonic is present over a very wide area.

My first attempts (calling the station, writing a letter) have been met
with no acknowledgment that there is a problem (it is not even obvious
that anyone understands that there MIGHT be a technical issue to pass
on to engineering.)

Any advice?

Tim.