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Entry  Sat Sep 2 01:38:27 2017, Craig, DailyProgress, BEAT, Sept 1st Calibrated Spectrum 20170902_005925_CalibratedSpectrum.pdf20170902_003309_OLG_from_PLL_EXC_to_OUT2_02-09-2017_000601.pdf20170902_001540_PLL_EXC_to_OUT2_02-09-2017_000601.pdf20170901_235334_TransBeatnote_5MHzStop_01-09-2017_234323.pdf
    Reply  Sat Sep 2 13:01:22 2017, awade, DailyProgress, BEAT, Re: Sept 1st Calibrated Spectrum 
Message ID: 1892     Entry time: Sat Sep 2 13:01:22 2017     In reply to: 1891
Author: awade 
Type: DailyProgress 
Category: BEAT 
Subject: Re: Sept 1st Calibrated Spectrum 

Great. Its probably ok to use a (slightly) larger slope on the Marconi ext modulation input for now.  I guess we should have some number estimates on the noise at different settings to 'calibrate' our understanding on how much benefit there is in going to lower and lower values. A quick nasty fix would be to hook up an ethernet box to the marconi and send GPIB commands to adjust the abolute frequency of the carrier to bring the PLL actuation signal back to the middle of range; I looked around and there weren't any python modules ready made so maybe not worth the time.  

The factor of two that you are seeing between the Aglient and the SR785 may have to do with their input impedance.  Aglient is 50 Ω and SR785 is 1 MΩ so the aglient will report a voltage times two from a 50 Ω output of the SR560 preamplifier. 

The calibration looks fancy but maybe unnecessary for a first pass? G/(1-G) => 1 well within the bandwidth of the PLL. So if we raise the PLL bandwidth to a decent frequency our in loop actuation signal should be a faithful representation of Hz/sqrt{Hz}.  I think just multiply the Hz/Vrms on the front panel display by 1/sqrt{2} is enough for a rough calibration.

Do we have any of the band passing filters turned on on the SR560. I'm not sure I understand why OLG is converging to two there.

 

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