So we've had an AT1800 (single channel receiver, so it's got diversity) for almost a year now. On random occasions we get an unusual noise pattern; signal sounds perfectly clean when talent is not speaking, but on the "edges" of words when speaking, there's a... what to call it... rattle... distortion... fuzz. (Mic used has no effect.) Before shooting we have the 1800 scan for a clear freq, but that has no impact on whether we'll get this noise. So we end up randomly picking a freq & seeing if there's that noise - an annoying process, even if we find a clean one on the first hit. Anyone else have this problem, and anyone know what's causing it?