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Reports until 14:50, Tuesday 07 August 2018
nolan.king@LIGO.ORG - posted 14:50, Tuesday 07 August 2018 - last comment - 08:58, Wednesday 08 August 2018(43296)
ISC Racks R1 and R2 Balun Replacements
Dick, Marc, Nolan

Replaced 6 baluns in ISC Racks R1 and R2. The insertion loss and phase shift through each balun was measured prior to installation, and compared to the phase shift through removed balun. Serial numbers, locations, bode plots and phase differences for each are annotated in the attached file (Doc and PDF formats). Noise measurements are attached, with most recent measurement (Aug 7, 2018) after replacement of final 6 baluns in green. 
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Comments related to this report
gabriele.vajente@LIGO.ORG - 15:39, Tuesday 07 August 2018 (43299)

[Hang, Gabriele]

We noticed that some of the signals (in particular LSC-POPAIR_B_RF18 and LSC-POPAIR_B_RF90) got different offsets. We put the IMC offline and retuned the dark offsets.

H1:LSC-TR_X_QPD_B_SUM_OFFSET and H1:LSC-TR_Y_QPD_B_SUM_OFFSET had to be tuned manually, since the script was not accurate enough (or did the wrong things, we did not investigate further)


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rich.abbott@LIGO.ORG - 16:05, Tuesday 07 August 2018 (43301)ISC
Hi Hang and Gabriele,
I was looking at the offset timeseries for this change, and it seems that the offset got larger after the balun change.  Is this what you see too?  I would have hoped that offsets get smaller if the ambient static RF field is reduced.  Nothing is obvious in this stuff.
gabriele.vajente@LIGO.ORG - 16:46, Tuesday 07 August 2018 (43303)

Actually, the offsets changed only slightly. See plot below.


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marc.pirello@LIGO.ORG - 08:58, Wednesday 08 August 2018 (43316)

Due to some lower limits of the RTL-SDR RF antenna, only the 27 MHz and the 45 MHz "before and after" RF scans came out correctly.  With the improved balun the 27 MHz leakage is significantly better.  The 45 MHz leakage appears to be slightly worse...  I second Rich's claim that "nothing is obvious in this stuff."

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