[ntp:questions] NTP absolute accuracy?

Unruh unruh-spam at physics.ubc.ca
Mon Nov 2 03:12:59 UTC 2009

John Hasler <jhasler at newsguy.com> writes:

>Bill Unruh writes:
>> Sorry, at 10usec, the distance away of the transmitter must be less than 3 km.

>10usec at the transmitter.

>> Also your system needs to see the start of the tone to 10usec which
>> means that the tone would have to be about 1MHz which is a bit beyond
>> audio.

>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.

Ie how fast is the carrier actually switched off and on. It cannot be
instantaneous or the signal would spill out badly into neighbouring bands. 

>John Hasler 
>jhasler at newsguy.com
>Dancing Horse Hill
>Elmwood, WI USA

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