The combination of amplitude modulation of the nuclear rf power at a frequencyf1and 180° modulation of the phase of the resonance microwave signal with respect to the reference microwave signal at a frequencyf2, wheref1≫f2, with successive amplification and phase sensitive detection at the two frequencies, has proved useful in electron‐nuclear double resonance (ENDOR) of unordered solids. The alternative of amplitude modulation alone often results in poor baseline stability, and the alternative of amplitude modulation plus magnetic field modulation results in the complication of summing in an uncontrolled manner ENDOR contributions from crystallites resonating at different fields and with different orientations with respect to the applied dc magnetic field.