Dan Hoak asked me about upconversion around the OMC dither lines at 575.1 Hz, 600.1 Hz, 625.1 Hz and 650.1 Hz, since the upconversion seen in L1 has been quite large at those frequencies (amplitude and band size). 

We don't yet have the long stretches of DC readout data used to look at L1 lines, but a quick look at the Feb 26 H1 lock confirms that upconversion around dither lines in H1 is large too. Plots made with ldvw are attached. The fine structures around 575.1 and 600.1 Hz are nearly identical to each other. The same goes for 625.1 and 650.1 Hz, but their structures differ significantly from those of the two lower-frequency bands. 

To repeat a comment made in the LLO alog originally, CW searches in such severely contaminated bands are pointless. We CWers hope that the bands affected by the dithers can be shrunk before O1 begins. (Of course, there are many more pressing issues to address before that...)