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Entry  Wed Apr 27 18:14:48 2011, kiwamu, Update, LSC, preparation for DRMI locking : RF status RF_Work_Status.png
    Reply  Wed Apr 27 21:08:08 2011, rana, Update, LSC, AS11 AS11.png
    Reply  Mon May 2 15:53:27 2011, kiwamu, Update, LSC, PRMI locking prep : demodulation boards RF_Work_Status.png
Message ID: 4576     Entry time: Wed Apr 27 21:08:08 2011     In reply to: 4574
Author: rana 
Type: Update 
Category: LSC 
Subject: AS11 

I worked on AS_11 today. Its ready for its noise / optical gain calibrations. I have left it on Suresh's desk.

AS11.png

This was one of the 24.5 MHz Black Box (Ben Abbott) style RFPDs rescued from LLO. The tunable inductor that was installed was too small to get the frequency down to 11 MHz and so I swapped in one of the shielded, ferrite core ones from our '7mm' CoilCraft kit. It had a range of 1.2 - 1.8 uH according to the datasheet.

I wasn't able to simulataneously get the peak at 11.06 MHz and the notch at 59.3 MHz and so I took Koji's advice and tuned the peak best. The plot above shows how the notch is slightly off. I think its not a problem; to get it better we would have to change out the inductor for the "2-omega" notch, but I was too lazy. The thinking is that its more important to have the gain be symmetric around the signal readout frequency so as to not imbalance the audio sidebands.

Since this one is going to be AS_11, we think that the 22 MHz signal will be tiny: the transmission of the 11 MHz sidebands to the dark port is small. If we later want to put in a 22 MHz notch anyway, there is space to do this via the 'active notch' pads around the MAX4107.

For the above plot, I used the Jenne laser. The DC output of the PD was ~30 mV (~0.6 mA). The RF drive to the laser was -10 dBm: no saturations. I have calibrated out the cable responses, but not using the 1811 setup, so the absolute calibration has yet to be done.

Also, it needs some new stickers. It would be handy if someone can figure out how to get some sheets of stickers that we can put into the printer. Then we can laser printer all of the data onto the stickers and stick them to the RFPD box.

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