The master GPS clock has been switched from the internal GPS unit of the master/fanout chassis to the external Trimble unit. This simply required to connect the 1PPS ouptut of the new GPS unit to the 1PPS input of the master/fanout chassis. Plot 1 shows that this proceeded with a small 100ns transient in the OCXO error signal but otherwise went smooth without interruption of the timing distribution system.

Plot 2 shows 1 day of second plots trending the difference between the atomic clock and the internal GPS (DIFF_1), the difference between the NTP server and the internal GPS (DIFF_2) and the difference betrween the Trimble and the internal GPS (DIFF_3). The atomic clock was shifted by +1µs and the NTP server by +0.65µs to shift the histograms towards the origin. This measurement was done before the switch over still using the internal GPS as the master. The Trimble unit seems to have about twice the variance compared to the internal GPS and the NTP server. The difference between the Trimble unit and the internal GPS is about 25ns.