[time-nuts] HP 5370B vs SR620

[Roy Phillips]

Pete
Thanks for the information.
Regards
Roy

----- Original Message ----- 
From: "Pete" <peterawson at earthlink.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Tuesday, May 19, 2009 3:27 PM
Subject: Re: [time-nuts] HP 5370B vs SR620


> Roy,
>
> The 5370s have a few quirks that you should know about to avoid
> possible surprises. These aren't newly discovered & have been the
> subject of various postings a few years ago.
>
> 1) Both instruments have some front end coupling with the data path
>    & the timebase. This was mostly corrected in the 5370B.
> 2) Both instruments have a low level issue with non-linearity of the
>    interpolator which provides the ~20ps resolution.
>
> The result of these imperfections is jitter readings taken on the 
> reference output signal (this is used in performance verification)
> will display the lowest readings you'll ever see. Real world signals
> locked to this source behave the same way. These readings are
> satisfying, but not real. When H-P spec'd the jitter floor at 30-
> 35ps, that's the true performance limit. Still quite good by any
> measure.
>
> Another candidate counter you should check out is the Fluke/
> Pendulum PM6681. These aren't common, but sometimes are
> on *bay for reasonable ($500-600) prices. This is a much more versatile 
> instrument than the 5370s with lower front end
> noise, thus somewhat better jitter floor.
>
> Regards,
> Pete Rawson
>
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