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Entry  Tue Nov 11 01:38:23 2014, Koji, Update, LSC, Notch at 110MHz twin_t_notch.pdfnotch_tf.pdf
    Reply  Wed Nov 12 00:55:56 2014, ericq, Update, LSC, Notch at 110MHz 165_Notched.pdf
Message ID: 10699     Entry time: Wed Nov 12 00:55:56 2014     In reply to: 10695
Author: ericq 
Type: Update 
Category: LSC 
Subject: Notch at 110MHz 

Quote:

Q >> Please measure the RF spectrum again with the notch. 

The notch filter has been installed directly attached to the output of the SHP-150 at the PD output. Structurally, there is a right angle SMA elbow between the two filters; I set up a post holder under the notch pomona box to prevent torque on the PD. Via directional coupler and AG4395, we measured the output of the REFL165 RF amplifier with the PRMI locked on REFL33. 

Note, the plot below is not referred to the amplifier output, as in my previous plots; it is directly representative of the amplifier output spectrum. 

165_Notched.pdf

There are no RF signals being output above -28dBm, thus I am confident that we are not subject to compression distortion. 

Given the last measurements we made (ELOG 10692), I estimate that the notch has reduced the power at 110MHz by ~33dB, which is 9dB higher than the notch performance Koji measured when he made it. Maybe this could be due to the non-50Ohm impedance of the HPF distorting the tuning, or I physically detuned it when mounting it on the PD. Still, 33dB is pretty good, and may even give us room to amplify further. (ZRL-700+ instead of the ZFL-1000LN+?)

 

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