The aim of the paper is to study experimentally the poloidal mode number (m) spectrum produced by a single toroidal mode number (n) Neoclassical Tearing Mode, showing how the sidebands of this spectrum may interact together via magnetic coupling, and how this multiple resonant structure interacts with the plasma, this could give a new point of view to understand the stability properties of these modes. In fact we expect that these sidebands, having different m numbers from the main one, can resonate inside the plasma at different radial positions: for example a n = 1, m = 2 mode produces m = +/-1 sidebands, which may lead to the formation of other magnetic islands at q = (m+1)/n, (m-1)/n = 3, 1.