[ntp:questions] Why does the "Conrad parallel port radio clock" driver has a standard offset of 0.1725s?

Martin Burnicki martin.burnicki at meinberg.de
Wed Jan 2 11:39:05 UTC 2008


Folkert van Heusden wrote:
> While going through the documentation we found that the "Conrad parallel
> port radio clock" driver has a default offset calibration factor of
> 0.1725s.
> Why is that specific factor chosen?

I bet this has been determined by a measurement. The DCF77 amplitude is
lowered at the beginning of a new second. Most cheap receivers detect the
second change when the amplitude has dropped below a certain limit. The
delay of this depends strongly on the bandwith of the transmitting and
reeiving antenna and circuit.
> This is especially interesting as my GPS has an offset of -0.173s! Is
> that a coincidence?

I'm sure it does. You might try to "fudge time1" for that particular device,
if the driver supports that.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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