As you surmise, it works to some extent like SNRM. It fluctuates all the time, probably in near-tandem with SNRM, but with finer movements. At one time it was the indicator I used when looking to re-sync for higher speed.
The indispensable man or woman passes from the scene, and what happens next is more or less the same thing as was happening before.
My broadband basic info/help site - www.robertos.me.uk.
Domains, site and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync 58162/14182kbps @ 600m. - BQM