There would be a moire pattern of regions of roughly the dimensions of a wavelength (~3 meters) within which interference would be mainly constructive or mainly destructive. Reception would suck or not exist in all the regions where interference was not constructive. Then the usual multi-path interference issues.​ Complicated and a good reason to keep transmitters well spaced-out. To do this right you are pretty much building a phased-array antenna which uses the interference intentionally to aim the beam by varying the synchronization among the signals from the different antennas and that is way too complicated for this - you have to track the location of the receivers somehow for one thing, and that's just the beginning.