Going back to investigations last week on in-band line artifacts due to aliasing of higher frequency DCPD channel artifacts (see LHO aLOG 82329), here we check the 16 kHz data of H1:OMC-DCPD_[A|B]_OUT_DQ against the saved reference spectra of DCPD B on ADC channels 1, 5, 9, and 13. Attached are spectra showing:

1. 1 Hz - 7000 Hz
2. 20 Hz - 100 Hz
3. 100 Hz - 500 Hz
4. 500 Hz - 1000 Hz
5. 1000 Hz - 1500 Hz
6. 1500 Hz - 2000 Hz
7. 2000 Hz - 7000 Hz

One can see man and a lot of artifacts that are visible in the 16k channels, but not visible in the 524k channels. In addition, the DCPD A sum channel artifacts appear larger than DCPD B sum channel artifacts. As mentioned in the previous aLOG, spending some time watching the time variability of the artifacts, the artifacts change amplitude and frequency over time. The higher frequency bands show a lot of artifacts, more in the A channels, and the artifacts in question do not appear in the 524k channels.

Solving these issues, perhaps with stronger suppression through digital filtering, would be greatly beneficial to searches for persistent, narrowband gravitational wave signals.