[time-nuts] Why are 1PPS signals so skinny?

[Azelio Boriani]

Simply dividing the 10MHz by a binary counter and taking the most
significant bit for the PPS leads to a 161.1391mS pulse.

On Tue, May 15, 2012 at 9:26 PM, Don Latham <djl at montana.com> wrote:

> Came to this thread late. Could it be thin because the end output of
> even a synchronous  dividing chain needs to be resynced to the beginning
> to maintain phase?
> Don
>
>
> shalimr9 at gmail.com
> > The Thunderbolt's output impedance is much less than 10 ohms. However,
> > it is only necessary to filter the end of the line for a clean pulse.
> >
> > See http://www.ko4bb.com/Test_Equipment/CoaxCableMatching.php
> >
> > I used the Thunderbolt's PPS output as a source in those measurements.
> >
> > Didier KO4BB
> >
> > Sent from my BlackBerry Wireless thingy while I do other things...
> >
> > -----Original Message-----
> > From: Said Jackson <saidjack at aol.com>
> > Sender: time-nuts-bounces at febo.com
> > Date: Mon, 14 May 2012 19:02:51
> > To: Tom Van Baak<tvb at leapsecond.com>; Discussion of precise time and
> > frequency measurement<time-nuts at febo.com>
> > Reply-To: Discussion of precise time and frequency measurement
> >       <time-nuts at febo.com>
> > Cc: Discussion of precise time and frequency
> > measurement<time-nuts at febo.com>
> > Subject: Re: [time-nuts] Why are 1PPS signals so skinny?
> >
> > These types of pulses should be routed as open-ended source-terminated
> > reflected wave switched transmission lines. Power will only flow for
> > nanoseconds as the pulse travels over the line. There won't be a drop of
> > 50% of the voltage at the target and no large power spikes in the unit
> > or requirements for proper impedance matching at the receiver side.
> >
> > Some units like the thunderbolt look quite bad driving a 50 ohms
> > transmission line, others that are designed with proper 50 ohms series
> > impedance create a sharp nice signal.
> >
> > Bye,
> > Said
> >
> >
> >
> >
> > Sent from my iPad
> >
> > On May 14, 2012, at 17:21, "Tom Van Baak" <tvb at LeapSecond.com> wrote:
> >
> >> Mark,
> >>
> >> I too once preferred 50% duty cycle 1 Hz signals because they seemed
> >> more "natural". But one day during an experiment where I was comparing
> >> a large set of clocks I noticed my lab's digital AC power meter was
> >> jumping by tens of watts every second.
> >>
> >> When a dozen DUT generate 1PPS along with as many REF pulses (via
> >> cascaded pulse distribution amps) and then these all go to both inputs
> >> of a TIC and there's also LED's on both TIC channels as well as the
> >> dist amps, the net load is enormous. The last thing you want in a
> >> precision timing lab is to load your AC line down exactly once a
> >> second. Remember 5V into 50R is 0.1 Amps. That was a modest amount of
> >> current in the 1950's, but massive overkill today.
> >>
> >> So that's why I now prefer short (e.g., 1 ms or 10 us) pulses.
> >>
> >> /tvb
> >>
> >>
> >> _______________________________________________
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> >
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>
>
> --
> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> R. Bacon
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
>
>
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
> POB 134
> Huson, MT, 59846
> VOX 406-626-4304
> www.lightningforensics.com
> www.sixmilesystems.com
>
>
>
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