40m
QIL
Cryo_Lab
CTN
SUS_Lab
TCS_Lab
OMC_Lab
CRIME_Lab
FEA
ENG_Labs
OptContFac
Mariner
WBEEShop
|
40m Log |
Not logged in |
 |
|
Wed Nov 18 22:49:06 2020, gautam, Update, ASC, Some thoughts about AS WFS electronics
|
Sun Nov 22 21:09:37 2020, gautam, Update, ASC, Planned mods for WFS head  
|
Wed Nov 25 18:18:41 2020, gautam, Update, ASC, Planned mods for WFS head 
|
Sat Nov 28 21:44:53 2020, rana, Update, ASC, Planned mods for WFS head
|
Thu Dec 10 22:46:57 2020, gautam, Update, ASC, WFS head assembled 
|
Thu Dec 17 15:23:56 2020, gautam, Update, ASC, WFS head characterization    
|
Wed Nov 25 18:30:23 2020, gautam, Update, ASC, Some thoughts about AS WFS electronics
|
Wed Dec 2 23:07:19 2020, gautam, Update, ASC, Electrical LO signal for AS WFS
|
Thu Dec 3 11:02:35 2020, rana, Update, Electronics, Electrical LO signal for AS WFS
|
Thu Dec 3 13:55:52 2020, Koji, Update, ASC, Electrical LO signal for AS WFS
|
Thu Dec 3 20:38:46 2020, gautam, Update, ASC, Electrical LO signal for AS WFS  
|
Thu Dec 3 21:14:38 2020, Koji, Update, ASC, Electrical LO signal for AS WFS
|
Thu Dec 3 21:44:49 2020, gautam, Update, ASC, Electrical LO signal for AS WFS
|
Fri Dec 4 03:02:40 2020, Koji, Update, ASC, Electrical LO signal for AS WFS
|
Fri Dec 4 22:41:56 2020, gautam, Update, ASC, Freq Gen Box revamp
|
Sat Dec 5 20:44:35 2020, gautam, Update, ASC, Freq Gen Box re-installed 6x
|
Mon Dec 7 12:38:51 2020, gautam, Update, IOO, IMC loop char  
|
Mon Dec 7 22:54:30 2020, gautam, Update, LSC, Modulation depth measurement
|
Sat Jan 16 18:59:44 2021, gautam, Update, LSC, Modulation depth measurement   
|
|
Message ID: 15704
Entry time: Thu Dec 3 20:38:46 2020
In reply to: 15702
Reply to this: 15705
|
Author: |
gautam |
Type: |
Update |
Category: |
ASC |
Subject: |
Electrical LO signal for AS WFS |
|
|
I removed the Frequency Generation box from the 1X2 rack. For the time being, the PSL shutter is closed, since none of the cavities can be locked without the RF modulation source anyways.
Prior to removal, I did the following:
- Measured powers at each port on the front panel
- Gigatronix power meter was used, which has a maximum power rating of 20dBm, so for the EOM drive outputs which we operate closer to 25-27 dBm, I used a 20 dBm coupler to make the measurement.
- Attachment #1 summarizes my findings - there doesn't seem to be anything majorly wrong, except that for the 11 MHz EOM drive channel, the "7" setting on the variable attenuator doesn't seem to work.
- We can probably get a replacement from MiniCircuits, but since we operate at 0dBm variable attenuation nominally, maybe we don't need to futz around with this.
- Measured the relative phasing between the 11 MHz and 55 MHz signals using an oscilloscope.
- I measured the relative phase for the EOM drive channels, and also the demod channels.
- The scope can accept a maximum of 5V RMS signal with 50ohm input impedance. So once again, I couldn't make a direct measurement at the nominal setting for the EOM drive channel. Instead, I used the variable attenuator to set the signal amplitude to ~2V RMS.
- I will upload the time-domain plots later. But we now have a record of the relative phasing that we can try and reproduce after making modifications. FWIW, my measured phase difference of 139 degrees is reasonably consistent with Koji's inferred from the modulation spectrum.
One thing I noticed was that we're using very stiff coax cabling (RG405) inside this box? Do we need to stick with this option? Or can we use the more flexible RG316? I guess RG405 is lower loss, so it's better. I can't actually find any measurement of the shielding performance in my quick google searching but I think the claim on the call yesterday was that RG405 with its solder soaked braids offer superior shielding.
Before doing any modification you should check how much the distributed powers are at the ports.
Also your modification will change the relative phase between 11MHz and 55MHz.
Can you characterize how much phase difference you have between them, maybe using the modulation of the main marconi? And you might want to adjust it to keep the previous value (or any new value) after the modification by adding a cable inside?
|
|
|
|
|
|
|
|