[time-nuts] HP 5370B
magnus at rubidium.dyndns.org
Sat May 10 14:08:24 EDT 2008
From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] HP 5370B
Date: Sun, 11 May 2008 00:15:34 +1200
Message-ID: <482591E6.4070806 at xtra.co.nz>
> Magnus Danielson wrote:
> >> Mark,
> >> The 5335 is specified at 9 digits/second of resolution, the 5370 is
> >> specified at 12 digits/second.
> > That is severly overoptimistic on the 5370's part and just about overoptimistic
> > on the 5335's part. I think you should not use those sales-numbers, as they are
> > there to give you a one-figure-of-merit hint, but they are not qualitative
> > values.
> >> That's 3 orders of magnitude better resolution. That brings up noise that at
> >> 9d/s is simply negligible.
> > I'd suspect something like 40 times better, not 1000 times better.
> > The 5335 singel-shot resolution is 500 ps while the 5370 has 25 ps, a factor of
> > 20. The front-ends is not that good on the 5335 thought, so let's add some
> > noise there.
> > I could make some tests if you like...
> Actually the 5370 single shot resolution is 20ps, however the noise is a
> little larger than that.
Thanks for correcting that. My memory failed me there...
> It can be much larger if the input signal slew rate at the trigger point
> is much less than about 7.5V/us (input attenuation = 1X).
> The performance also deteriorates when the input amplifiers are severely
> Since the 5370 input amplifier noise bandwidth is 500MHz the wideband
> noise seen by the 5370 inputs should also be low.
Trigger jitter always adds, but single shot resolution limits the "digits
per second" fairly well.
> >> My two 5370s are rock stable if I only look at the 9 left-most digits.
> > Maybe you should trim your multiplier chain?
> Aligning the various filters in the 10MHz to 200MHz multiplier chain can
> make a considerable difference to the apparent noise.
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