I have heard this same frequency random heterodyne on 1100 kHz, WTAM was well aware of it too. The warble cadence is not precise but predictable. It almost sounds like an oscillator automatic frequency control (AFC) of some sort or the oscillator is just unstable. I don’t know how eastern European transmitter manufacturer’s frequency synthesis works or what stability methods they use if any, but just the way it sounds and what has been heard before, it makes me think it is simply a malfunction. It doesn’t take a lot of power to wreak havoc with a heterodyne over a wide area.