[time-nuts] Tbolt time constant

WB6BNQ wb6bnq at cox.net
Mon Oct 12 21:08:09 UTC 2009

Hi Tom,

Can you explain what is meant by "damping ?"

How is the "damping" related to the time constant ?

I gather from your referenced web page that it seems that a higher number was
better. Is this a correct assumption ?



Tom Van Baak wrote:

> > Does the longer time constant actually make a "better" frequency standard, or
> > does it just push the noise from one frequency region to another?  Has
> > anybody with gear good enough to measure close in noise looked at the
> > spectrum for different time constants?
> Hal,
> Last I checked - phase noise, as in L(f), is the same for all
> time constants.
> Frequency stability, as in sigma(tau), ADEV, etc. typically
> improves as the TC increases, out to 1000 s. The default of
> 100 s works pretty well for normal environments. But if your
> sat visibility and voltages and temperature and air currents and
> local seismic (vibration, shock, kids playing, doors closing, etc.)
> environment is unusually stable then you could bump the TC
> beyond 100, maybe even near 1000. I run my best TBolts
> closer to 300.
> For some time constant plots, see:
> http://www.leapsecond.com/pages/tbolt-tc/
> /tvb
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