Keita, Evan
We went into the PSL to see if we could find a source for today's 45 MHz glitches.
We didn't find anything conclusive. Mostly, it seems that bending the main cable (the LMR195 that carries the 45 MHz into the PSL) causes large glitches in the AM stabilization control signal, similar to what is seen by bending/tapping the LMR195 cable at ISC R1. We did not really see anything by bending the slow controls / power cables, or the rf cable that drives the EOM.
The main cable passes from the ISC rack, through the PSL wall, through the (overstuffed) cable protector on the HPO side of the PSL table, over the water pipes underneath the PSL, and then terminates at the EOM driver, which sits just underneath the PMC side of the table. Keita notes that the pipes don't seem to be vibrating.
It is worth noting that these glitches, which are clearly seen in the control signal time series of the EOM driver in the PSL, do not show up in the control signal time series of the spare driver hooked up in the CER.
After this, Keita and I went to the ISC rack, inserted a 20 dB coupler after the balun on the patch panel, and looked at the coupled output on a scope. We didn't see anything.
However, around the time that we inserte this coupler, it seems that the glitches went away. The attachment shows 12 hours of AM stabilization control signal. The first loud burst appears to coincide with the lockloss at 16:20 Z. The second loud burst around 19:40 was Fil and me wiggling the cable. The third loud burst around 23:30 is Keita and me in the PSL. The dc shift in the control signal around 00:30 is the time period with the coupler inserted.
When inserting the coupler, I noticed that the balun casing is slightly loose; I was able to twist the face of this casing just by unscrewing the cable from it.