Technical issue with Measured Phase Difference: x2 Ettus B200 minis

[911_Guy_inLA]

I am attempting to use two B200 minis at the same time to measure differences in amplitude and phase from a single signal over coax cable and a 3dB splitter. I am using gnu radio companion to run this radio setup. I am splitting a PPS signal and running to both radios. 

I am having issues in the measured phase difference. It seems that either radio is not locking to the reference (PPS), and the phase difference for the measured signal continues to vary as a function of time.

I have attempted the following:

• Use a 10MHz reference from my signal generator
• Running gnu radio as admin
• Issue a state timer using various delay, trigger, cycle time settings
• Using various sample rates and Rx IBW

Also, using a simulated source in gnu radio does produce the expected result. However, when I switch back to the radios the results are variable again. I'm beginning to think there might be an issue with the radios but would like to open a discussion to see what else we can try to get this setup going...

gnu radio setup and radio setup pictures are provided to aid discussion.