Anritsu MG3641A - Manual (Page 179)

SECTION 7 PERFORMANCE TEST
7-11
(5) Note on test
The demodulation zone of the modulation analyzer must be within 0.3 to 3 kHz at measurement of the modulation
factor and 0.3 to 15 kHz or 0.3 to 20 kHz at measurement of the distortion.