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Entry  Tue Nov 7 17:09:23 2017, Craig, awade, DailyProgress, PLL, Communication with Marconi through GPIB 
    Reply  Tue Nov 7 20:56:48 2017, Craig, DailyProgress, PLL, PLL Beatnote Tracking through GPIB 
Message ID: 1973     Entry time: Tue Nov 7 20:56:48 2017     In reply to: 1972
Author: Craig 
Type: DailyProgress 
Category: PLL 
Subject: PLL Beatnote Tracking through GPIB 

 

Quote:

Using EQ's netgpib infrastructure, I was able to communicate with our PLL Marconi remotely.  This will enable us to continually lock our PLL despite the crazy MHz-per-hour fluctuations in the trans beatnote frequency we see.

I added the script Marconi2023A_BeatnoteTrack.py to the labutils/netgpibdata/ git repo which tracks our transmission cavity beatnote in real time.

The script adjusts the Marconi carrier frequency as the PLL control voltage approaches too close to the rails.  The rails are defined within the script, and are not yet customizable, but it would be a very simple thing to do.

The script adjusts the carrier frequency up or down by the FM deviation value itself.  So if your FM deviation value is 10 kHz, like ours, then your carrier frequency of 90 MHz will be adjusted either down to 89.99 MHz or up to 90.01 MHz.  This is not robust, and other users will have to adjust the rails and the amount and direction of adjustment based on their personal setups.

I'm going to leave this running in our lab overnight while tracking with stripTool to see if anything crazy happens.  If the PLL somehow gets out of range, the script will shut itself off, so nothing bad will happen to our electronics.

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