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Entry  Mon Jun 22 20:59:19 2015, ericq, Update, LSC, DFD Delay length 
    Reply  Wed Jun 24 17:30:45 2015, ericq, Update, LSC, DFD Delay length 
Message ID: 11374     Entry time: Wed Jun 24 17:30:45 2015     In reply to: 11371
Author: ericq 
Type: Update 
Category: LSC 
Subject: DFD Delay length 

This afternoon, I had a fruitful conversation with Rich Abbott about various kinds of cables.

I've sent an email to Steve to ask him to buy 2 x 50m LMR-195 cables, with male SMA connectors. Rich highly recommends these for their polyethylene insulation, which makes them less microphonic and less susceptible to thermal expansion, low loss, and multi-ply bonded foil shielding.

50m means that the peak to peak mixer output swing corresponds to about a MHz. 1nV of mixer output noise looks like ~6mHz frequency noise, for a Level 3 mixer appropriately driven. As a comparison, the lowest our in-loop green PDH error signals get is 0.1Hz/rtHz. 

The cable attenuation should be around 4.2dB at 50MHz, and 7.3dB at 150MHz, according to the data sheet. Thus, we should not be in the regieme where we are losing sensitivity to the attenuation. 

By my rough geometric estimation, these two should fit in the 2U box I got ahold of today fine. Jessica is designing the front panel. 

We currently have ~30m of RG-408 and RG-142 as our delay lines. 

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