In a message dated 6/9/2007 23:54:50 Pacific Daylight Time, [EMAIL PROTECTED] writes:
>Measurements taken from 3325B at 1 MHz: >5370B reference: INT EXT (same 5087A as 3325B uses) >Square wave, 2v pk: 15-20 ps 11-12 ps >-- john, KE5FX Hi John, now I am jealous. I checked the switches, they all seem to work as required. Wanna trade :) ? Tom wrote: >What definition of jitter are you using? Are you looking at >every zero-crossing at 10 MHz? Or every Nth one? What >sample size? Or would you rather know the ADEV at tau >1 second? etc. >/tvb Hi Tom, the Wavecrest can be set up with arbitrary bin sizes. In this case it was 1000 measurements per bin I think (default setup). Going higher doesen't change the measurement much, and the Manual states the same. The unit uses zero crossings. I usually AC-couple square-waves into it. The unit calculates RMS jitter at the touch of a button, and I used all the standard settings. Not sure what the hold-off is, but it's asynchronous. Basically the unit starts as soon as it can after a stop event. The histograms I sent are averages of many measurements, there is some info in the picture. On a good oscillator the histogram is a perfect Gaussian curve, with about 2.7ps RMS jitter (basically the internal jitter noisefloor of my Wavecrest unit). I once correlated the results of the Wavecrest numbers with an Agilent 86100A 20GHz scope on my best OCXO, and the RMS jitter numbers were within 200femtoseconds of what the Wavecrest gave! Since the jitter is so large, any good scope should be able to show the 5370B jitter, such as a 54720D or similar (has about 60ps noise-floor if I remember correctly). The >200ps jitter on the 5370B should be visible on that, but then again maybe it's a fault in my unit :( I get about 100ps best case RMS jitter on my measurements with the internal OCXO, and about 30-50ps using a Fury as a reference. Still think besides the noisy time-base that the unit just needs a very careful calibration... I wonder who has the needed equipment to do a by-the-book calibration on these guys. bye, Said ************************************** See what's free at http://www.aol.com. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
