[ntp:questions] NTP absolute accuracy?

David Malone dwmalone at maths.tcd.ie
Tue Nov 3 09:24:46 UTC 2009

David Woolley <david at ex.djwhome.demon.invalid> writes:

>David Malone wrote:

>> The Rugby unit was built by Ian Dowse, and is described here:
>> 	http://www.maths.tcd.ie/~dwmalone/time/rugby.html

>This is a simple AM detector for the slow code (I don't know if the fast 
>code is still transmitted).  It doesn't phase lock onto the carrier.

Yep - It just delivers the pulses to DCD on a serial port. The
driver uses the PPS API and averages the second marks over the
minute before delivering the dates to NTP via the SHM driver.

I do have some software radio stuff that looks at various long wave
signals. Where I am, we can hear MSF, DCF, BBC 4 and TDF, all of
which carry time signals. I have some plots of the phase here:


You can clearly see the phase-modulated timecodes on top of BBC 4
and TDF. Josh Tobin did some work with me to write software decoders
for these over the summer, and had the TDF signal working as an NTP
refclock. We haven't cleaned the code up yet, but hope to soon.


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