The output level of the MG645B can be varied by a step dial and a vernier dial from 130dBµ (+17 dBm) to -30 dBµ (-143 dBm).
AM can be modulated up to 100% and FM up to 200kHz in deviation.

The Anritsu MG645B's carrier frequency has excellent accuracy and stability thanks to use of a high-performance counter and a phase lock loop (PLL) which can lock on the frequency corresponding to the frequency channel.