[time-nuts] Power supply for Thunderbolt

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Aug 5 21:14:03 EDT 2008

David C. Partridge wrote:
> I'm using the Meanwell T30-B, but Tom van Baak's test on this shows a bit of
> phase noise at 1Hz offset which is a tad nasty:
> http://www.leapsecond.com/pages/tbolt/noise.htm
> I'm wondering if this can be reduced with a bit of extra de-coupling on the
> 5V supply, but haven't got round to scoping the 5V supply to see what
> happens every second (presumably as the output is sent to the serial port).
> Cheers
> Dave

Interaction between the power supply switching noise components and 
internal frequencies in the thunderbolt could produce the 1Hz spur.
It would be useful to know the noise spectrum of the power supply 
outputs both at high and low frequencies.

Careful filtering of the HF components of the power supply noise may be 
effective in reducing such interactions.
Alternatively the supply could have a low level 1Hz oscillation 
superimposed on its output.

It may well be easier and more cost effective to just use a lower noise 
supply rather than adding the complexity and cost of low and high 
frequency filtering.


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