[ntp:questions] Re: Suppressing IP6; Keeping /dev/ppsX; simple MSF clocks and monitors

jonathan at uk.me.buzzard jonathan at uk.me.buzzard
Mon Nov 24 10:31:08 UTC 2003

In article <iojTDbCm8Hv$EwLf at nospam.oak-wood.co.uk>,
	Chris Hastie <chris at nospam.oak-wood.co.uk> writes:

> Simple MSF clocks and monitors
> ==============================
> I've noticed after producing a few graphs that my server synchronised to
> a simple MSF clock (the Jonathan Buzzard one) tends to be pretty close
> to other servers at times that I'm generally sat at the console but have
> offsets of around -1.6ms at other times. I couldn't see that I was
> somehow changing the load significantly, and there were odd times when
> the me-at-the-console sync continued all day although I wasn't at the
> console. After some pondering I hypothesised that sync was closer when
> the monitor was turned on. After leaving it on all day yesterday this
> does appear to be the case. Could anyone suggest a mechanism for this?
> Is it likely to be a simple as the magnetic field from the monitor
> affecting the radio clock such that re-positioning the radio clock
> further from the monitor will produce more consistent time? Or is the
> issue more likely to be in proximity of cables or some obscure thing
> inside the PC box?

It is almost certainly monitor related. You could try changing the
refresh rate, or alternatively you might just be stuck with the
fact that one or more of the switched mode power supplies in the
monitor is operating at 60kHz or some harmonic there of. In which
case the receiver board will take longer to decide there has been
a change in MSF signal which is what you are noticing. If this is
the case move the clock futher away from the monitor. I have
found that more height is also useful.


Jonathan A. Buzzard                 Email: jonathan (at) buzzard.me.uk
Northumberland, United Kingdom.       Tel: +44 1661-832195

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