If I lock multiple ADRV9009s to a common reference clock, are these channels phase locked for phase coherent FFH. If I tune from one frequency to a new frequency and back to the original do I get the original phase or is re-calibration needed?
Yes phase sync will operate, but depending on the dwell time, it may not have time to react. Phase sync is a slow loop that maintains the phase of the LO with respect to the input REF Clock and the loop dynamics are inherently slow by design to prevent fast phase changes when correction is needed.
Please refer to User guide section "RF PLL PHASE SYNCHRONIZATION" for more details.