In this paper, we have presented an experimental and numerical analysis of a 1 H DNP-NMR maser operating at 1.2 K. The unexpected experimental observations of distant dipolar field effects in this context can be explained by the presence of an efficient radiation feedback that leads to a persistent coherence of the magnetization on time scales of seonds or minutes. An analysis based on a classical model taking into account radiation feedback from the probe and the presence of a dipolar field, together with a simplified model for DNP polarization provided sound description of