If the two stations are really at the same frequency, the diode detector in the receiver can act like a synchronous detector, which has better signal-to-noise ratio than a diode detector for low signal levels. The local station acts like the local oscillator of the synchronous detector. Of course, the two frequencies will not actually be exactly the same, and there will be interference in the form of flutter or fading between the stations because of the varying difference in phase of the carriers. The sidebands of the local station will also cause interference with the distant station.