[time-nuts] trimble Thunderbolt, how to get 25 or 27 mHz from it??

Attila Kinali attila at kinali.ch
Mon Jan 8 09:12:07 EST 2018

On Mon, 8 Jan 2018 13:14:16 +0000
Chris Wilson <chris at chriswilson.tv> wrote:

> Thanks for the very fast reply! Would it be possible to use one of
> these frequency multiplier IC's? Sounds simpler, but maybe there are
> down sides?
> http://uk.farnell.com/on-semiconductor/nb3n502dg/pll-clock-multiplier-8soic/dp/2101849

Bruce's idea is much lower noise. The NB3N502 datasheet states
an typical output jitter of 15ps. That's HUGE for a normal VCXO
output that is usually below 1ps. The low-noise OCXOs have something
in the order of 100fs. Alternatively, you can use something like
an ADF4002 and an VCXO with 25/27MHz. That should give you a much
better performance, mostly limited by the VCXO. But you will need
to have a sine-to-square conversion of the 10MHz output of the
Thunderbolt first, as the ADF4002 has a slew-rate limit on its
reference input.

BTW: stay away from any VCXO that mentiones "programable" in its datasheet.
These are XO + fractional PLL combinations where the PLL allows quick
and cheap realization of odd frequencies. But their spurs and noise floor
is much worse than normal XOs.

			Attila Kinali

It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson

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