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Entry  Sun Jan 30 19:26:03 2011, Koji, Summary, Green Locking, Prototype freq divider freq_divider.pdfIMG_3813.jpgIMG_3814.jpg
    Reply  Wed Feb 2 03:27:20 2011, Koji, Summary, Green Locking, 85MHz Freq divider freq_divider.pdfIMG_3816.JPGIMG_3818.JPG
       Reply  Wed Feb 2 09:56:55 2011, Koji, Summary, Green Locking, Installed the freq divider and Rana's PFD freq_divider_installation.pdf110201_freq_divider_output.pdf
          Reply  Wed Feb 2 10:44:26 2011, Koji, Summary, Green Locking, Freq fluctuation measured by the freq divider and Rana's analog PFD 110201_green_freq_fluctuation.pdf
             Reply  Wed Feb 2 12:55:34 2011, Koji, Summary, Green Locking, Freq fluctuation measured by the freq divider and Rana's analog PFD 
             Reply  Sat Feb 5 23:03:04 2011, rana, koji, Summary, Electronics, Analog Frequency Discriminator: splitter + mixer + long cable mixer.pdfUntitled.pngfsm.png
                Reply  Sun Feb 6 02:29:28 2011, rana, Update, Electronics, Analog MFD: longer cable mfd18.png
Message ID: 4255     Entry time: Sun Feb 6 02:29:28 2011     In reply to: 4254
Author: rana 
Type: Update 
Category: Electronics 
Subject: Analog MFD: longer cable 

I swapped over to a 3x longer cable (old 65 ft. Pasternak cable from ancient 40m days). The old one was 6m, the new one is 18.2 m. It was already coiled up so I put it into a tupperware box to shield it somewhat from the HVAC wind.

The noise went down nearly proportional to the length (after I recalibrated the DAQ channel for the ~3x higher phase->voltage gain). With this length, the peak-peak mixer range is 5.5 MHz, so still enough to go an FSR here.

mfd18.png

I give credit to the low frequency improvement entirely to Tupperware for their excellent containers. The current noise limit is most likely the SR560.

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