[time-nuts] 1PPS for the beginner

Dana Whitlow k8yumdoober at gmail.com
Wed Aug 15 08:38:48 EDT 2018


On Peter Vince's topic, *does anybody in the group know what part of the*
*waveforms transmitted by WWV & WWVB mark the second boundaries?*

I was once comparing the timing of PPS pulses from a GPS receiver with
WWV's ticks, and saw about 5 msec delay to the ticks (in south central
Texas).
Obviously propagation and my receiver's internal delays account for most
of that, but I never could decide which part of the audio waveform I should
be referencing.

For WWV, I feel that the best choice would be the central peak in the
response
of a matched filter designed around the tick waveform, but I bet "they" did
something entirely different.  Hence the question posed above.

Dana


On Wed, Aug 15, 2018 at 7:22 AM, Peter Vince <petervince1952 at gmail.com>
wrote:

> I was astonished to see the pulse-width in the document defined from the
> base of the (sharp-cornered!) edges, and not the mid-point - totally
> impractical!  Near the top of the previous page it says: "If required for
> testing purposes, the pulse width at the 50% level may be determined by
> extrapolation."  Now OK, the very wide tolerance on the pulse-width makes
> this all rather academic, but surely that spec wasn't written by an
> engineer? :-)
>
>      Peter
>
> On 15 August 2018 at 05:03, Björn <bg at lysator.liu.se> wrote:
>
> > Hi Bernd,
> >
> > One reference to 20us 1PPS pulse length is the ICD-GPS-060, see figure
> > 3-2, page 3-3 (pdf page 19)
> >
> > https://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf
> >
> > Group - Are there other standard documents defining duty-cycle, voltage
> > levels, rise times etc?
> >
> > MfG
> >
> >      Björn
> >
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