[ntp:questions] NTP absolute accuracy?

Terje Mathisen Terje.Mathisen at tmsw.no
Mon Nov 2 07:23:42 UTC 2009


Unruh wrote:
> John Hasler<jhasler at newsguy.com>  writes:
>> There isn't any tone.  It's the UK equivalent of WWVB.
>
> How is the beginning of the second ( an hour) marked?
> The bandwidth of whatever marks it has to be pretty narrow, or the transmitter
> would interfer with everything around it. Ie, that means a large time uncertainty.

Not if they do the same spread spectrum modulation of the carrier as 
emplyed by the German DCF77 transmitter: By phase-locking a receiver to 
that signal, you can get down to the 10-30 us or so range.

(You still have to be close enough to the transmitter so that the 
propagation path is perfectly predictable, otherwise you'll see 
systematic excursions as a function of the time of day/night.)

Terje

-- 
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"




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