[time-nuts] Upper limit on phase noise from two oscillators.

Dr. David Kirkby drkirkby at medphys.ucl.ac.uk
Wed Apr 27 18:12:30 EDT 2005

Dr. David Kirkby  Ph.D. CEng MIEE,
Senior Research Fellow,
Department of Medical Physics and Bioengineering,
Malet Place Engineering Building,
Gower St,
University College London,
Tel: 020 7679 0273

On Wed, 27 Apr 2005, Tom Van Baak wrote:

> > If I have two different oscillators (HP 10811A & 10811-60111) can I work
> > out an *upper* limit of the phase noise on one of the oscillators. I
> > think I can, but will not know what oscillator is the worst.
> Correct. If you use 3 oscillators you can find which
> is best/worse.
> Now is low phase noise really what you're after, or
> are you more interested in low short- and long-term
> Allan Deviation?
> /tvb


In the short term I just want to build an accurate oscillator that use
with the time-interval counter to get a second oscillator (for my
pendulum clock) on frequency.

That is why for a quick solution I have bought the rubidium oscillator, as
that will be good enough, without locking to GPS, for what I initially

The pedulum clock just needs long term stability of course, but I think a
TXCO will be sufficient, and an oven a bit OTT.

In the longer term, I am likely to have other uses for a decent
oscillator. I have some sig gens and a microwave counter.  I might at some
point in time use it for a reference for a 10GHz ham project, in which
case phase noise would be critical. I don't really know what in the long
term I will use this for.

I found that Shera's article interesting, so thought why I am putting
something together, I might as well make the best job of it I can. Hence I
will lock a crystal and/or the rubidium to a GPS.

I suspect there are compromises, but my knowledge of this is not great, as
you can guess.

David Kirkby

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