Jitter question

• Jitter question
  Posted by jimon on 24 Jan, 2015 12:03
• Question repost from here (Haven't got answer there, but I'm really curious).
  
  I'm playing around with modified FE-5680b frequency standard (modified to output 60 MHz instead of 1 pps, but I've checked other internal frequencies also, 20 MHz, 30 MHz). I'm using hacked DS1054Z.
  
  So if I trigger on this 60 MHz and then scroll for couple of microseconds then the waveform start to look really jittery, is it a issue with time domain oscillator in the scope ? Or maybe it's a limitation of scope trigger circuit ? I assume frequency standard is named "standard" for a reason
  
  Also exactly the same happens when I play around with cheap AD9850 DDS from ebay.

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• #1 Reply
  Posted by wraper on 24 Jan, 2015 12:22
• Update to the latest firmware. Dave even made a video about this.
• #2 Reply
  Posted by jimon on 24 Jan, 2015 14:19
• Yep, update have fixed this issue. 
  Thanks for the help !
• #3 Reply
  Posted by c4757p on 24 Jan, 2015 14:45
• Quote from: jimon on 24 Jan, 2015 12:03

  So if I trigger on this 60 MHz and then scroll for couple of microseconds then the waveform start to look really jittery, is it a issue with time domain oscillator in the scope ? Or maybe it's a limitation of scope trigger circuit ? I assume frequency standard is named "standard" for a reason
  
  Also exactly the same happens when I play around with cheap AD9850 DDS from ebay.
  

  
  For what it's worth, these Rb standards actually can have fairly bad jitter, they're just super-accurate with a little bit of averaging. But it's not that bad. I'd expect the AD9850 to have quite poor jitter performance at certain frequencies, particularly approaching the maximum (that's inherent in DDS chips running from a fixed clock, nothing wrong with the AD9850), so don't worry if you still see that.