evan.goetz@LIGO.ORG - posted 14:11, Thursday 02 May 2024 - last comment - 14:27, Tuesday 07 May 2024(77579)
DuoTone signal seen in h(t)
This may already be known, but in case it is not I am posting it in the aLOG again. In Fscan spectra, we can see the 960 Hz and 961 Hz DuoTone signal in h(t). I don't recall seeing this in previous observing run data. Is the DuoTone signal expected to be seen in h(t)? It is hard to see on the summary pages, but it can be seen in the Fscan plots or interactive spectrum. I attach a zoom from the interactive plots from May 1, but this can also be seen as far back as the start of O4a. It is also seen at L1.
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Just wanted to add in a DARK spectrum as reference to this, indicating this is coming from the local electronics chain, and given I see some of this on the same ADC but non-DCPD channels, likely within the chassis itself. I also see even more of a 1 Hz forest than Evan's plot. See for example LLO alog: 71027.
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