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Entry  Wed Nov 18 22:49:06 2020, gautam, Update, ASC, Some thoughts about AS WFS electronics 
    Reply  Sun Nov 22 21:09:37 2020, gautam, Update, ASC, Planned mods for WFS head aLIGO_wfs_v5_40m.pdfTFs.pdfnoise.pdf
       Reply  Wed Nov 25 18:18:41 2020, gautam, Update, ASC, Planned mods for WFS head anodeVsOutput.pngsensitivity.png
          Reply  Sat Nov 28 21:44:53 2020, rana, Update, ASC, Planned mods for WFS head 
          Reply  Thu Dec 10 22:46:57 2020, gautam, Update, ASC, WFS head assembled aLIGO_wfs_v5_40m.pdfTF_meas.pdf
             Reply  Thu Dec 17 15:23:56 2020, gautam, Update, ASC, WFS head characterization oNoise.pdfZ_Hi.pdfZ_Low.pdfIMG_9030.jpgiNoise.pdf
    Reply  Wed Nov 25 18:30:23 2020, gautam, Update, ASC, Some thoughts about AS WFS electronics 
       Reply  Wed Dec 2 23:07:19 2020, gautam, Update, ASC, Electrical LO signal for AS WFS RF_Frequency_Source.pdf
          Reply  Thu Dec 3 11:02:35 2020, rana, Update, Electronics, Electrical LO signal for AS WFS 
          Reply  Thu Dec 3 13:55:52 2020, Koji, Update, ASC, Electrical LO signal for AS WFS 
             Reply  Thu Dec 3 20:38:46 2020, gautam, Update, ASC, Electrical LO signal for AS WFS RF_Frequency_Source.pdfdemodPath.pdfEOMpath.pdf
                Reply  Thu Dec 3 21:14:38 2020, Koji, Update, ASC, Electrical LO signal for AS WFS 
                   Reply  Thu Dec 3 21:44:49 2020, gautam, Update, ASC, Electrical LO signal for AS WFS 
                      Reply  Fri Dec 4 03:02:40 2020, Koji, Update, ASC, Electrical LO signal for AS WFS 
                         Reply  Fri Dec 4 22:41:56 2020, gautam, Update, ASC, Freq Gen Box revamp 
                            Reply  Sat Dec 5 20:44:35 2020, gautam, Update, ASC, Freq Gen Box re-installed 6x
                               Reply  Mon Dec 7 12:38:51 2020, gautam, Update, IOO, IMC loop char OLTFcomparison.pdfdemodMons.pdfOLTFcomparison.pdf
                               Reply  Mon Dec 7 22:54:30 2020, gautam, Update, LSC, Modulation depth measurement modDepth.pdf
                                  Reply  Sat Jan 16 18:59:44 2021, gautam, Update, LSC, Modulation depth measurement PLL.pdfmodDepth.pdfmodProfile.pdfEOMpath_postMod.pdf
Message ID: 15706     Entry time: Thu Dec 3 21:44:49 2020     In reply to: 15705     Reply to this: 15707
Author: gautam 
Type: Update 
Category: ASC 
Subject: Electrical LO signal for AS WFS 

I'm open to either approach. If the full replacement requires a lot of machining, maybe I will stick to just the 55 MHz line. But if only a couple of new holes are required, it might be advantageous to do the revamp while we have the box out? What do you think?

BTW, now that I look more closely at the RF chain, I have several questions:

  1. The 1 dB compression power of the ZHL-2 amplifiers is ~29 dBm, and we are driving it at that level. Is this okay? I thought we always want to be several dBm away from the 1dBm compression point?
  2. Why do we have an attenuator between the Marconi input and the first ZHL-2 amplifier? Can't we just set the Marconi to output 8 or 9 dBm?
  3. The Wenzel frequency multiplier is rated to have 13dBm input and 20 dBm output. We operate it with 12 dBm input and 19 dBm output. Why throw away 1 dBm?

I guess it is feasible to have +17 dBm of 55 MHz signal to plug into the Quad Demod chassis - e.g. drive the 55 MHz input with 20 dBm, pick off 3dBm to the front panel for ASC. Then we can even have several "spare" 55 MHz outputs and still satisfy the 9 dBm input that the ZHL-2 in the 55 MHz chain wants (though again, isn't this dangerously close to the 1dB compression point?). The design doc claims to have done some Optickle modeling, so I guess there isn't really any issue? 

Quote:

Are you going to full replacement of the 55MHz system? Or just remove the 7dBm and then implement the proposed modification for the 55MHz line?

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