UG-570 Rev A, page 15 says "The clock frequency must be between 5 MHz and 320 MHz...."
"The valid frequency range for the RFPLL phase detectors is 10 MHz to 80 MHz...."
The data sheet for the AD9361 rev F on page 5 says that the Reference Clock Input Frequency Range for the External Oscillator is 10 to 80 MHz. It also lists the signal level into the external port as 1.3 Vp-p. This tends to make one believe the frequency range is also for the external and not the PD.
My assumption is that the UG-570 is correct and the data sheet actually means the freq range of the PD and not the external reference. Can you please verify this?