Starting at 08:38 PST this morning the 1PPS signal from EY CNS-II clock, as seen by the comparitor, started dropping from is nominal range of -200 to -700 nS.

This had been seen before and was coming and going about every month about a year ago to the point where Erik installed a Rb clock under the computer rack at EY as a second independent clock and ran its 1PPS BNC into the next port on the comparitor, at which point the problem went away for 8 months until today.

The timeline for the past year is:

07dec2024 CNS dropped to -700 for a few hour

16jan2025 ditto

25feb2025 ditto

04mar2025 Rb clock installed

21nov2025 problem reappeared 8 months since last one

The Rb clock signal is a linearly varying time difference and it does not show any jump this morning confirming the CNS-II signal itself is the problem, not the comparitor or the local timing fanout.

In the trend posted CNS-II is BLUE, Rb-clock is ORANGE