[time-nuts] Stepping up the output of an OCXO

Magnus Danielson cfmd at bredband.net
Sun Feb 4 14:06:51 EST 2007

From: Dr Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] Stepping up the output of an OCXO
Date: Mon, 05 Feb 2007 01:22:54 +1300
Message-ID: <45C5D01E.5080508 at xtra.co.nz>

> Ulrich Bangert wrote:
> > Bruce,
> >
> > I have seen this specs before but do you know how to find the
> > schematics?
> >
> > Best regards
> > Ulric Bangert
> >
> >   
> Ulrich
> Since the earlier NBS isolation/distribution amplifiers consisted of dc 
> coupled cascaded common base stages (according to Magnus who had looked 
> at some),

One of the NBS/NIST articles is "Design Considerations in State-of-the-Art Signal Processing and Phase Noise Measurement Systems" by F.L. Walls, S.R. Stein, J.E. Gray, and D.J. Glaze:

See Fig 1 for the amp that I was talking about. Look - no coils!
I actually wander if they have not made a point of building it off 3 2N3904
rather than some more suitable transistor. I've seen similar stuff from these
culprits before.

> the newer generation developed in conjunction with the 
> technical university of Torino may merely use the same topology with 
> faster transistors (SiGe??) perhaps in IC or hybrid form.

Why not? ;O)

> I suspect that the 0.3ps/K may have been a typo and they use amplifiers 
> similar to the Spectradynamics Distribution amplifiers rated at 3ps/K. 
> These distribution amplifiers  are recommended by the BIPM.
> For the 1-20MHz amplifier see:
> http://www.spectradynamics.com/HPDA-15.html
> See attached files for phase noise plot and mechanical shielding used.
> I guess there's a passive splitter in there somewhere and a bandpass 
> filter (which probably contributes most of the phase tempco) in there as 
> well.

Indeed. Probably an initial boost, passive splitter and iso-amps.


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