On 2012-01-10, Terje Mathisen <"terje.mathisen at tmsw.no"> wrote: > unruh wrote: >> On 2012-01-10, David J Taylor<[email protected]> wrote: >>> pulse over the length of line he talks about should be no problem at all >>> (but a microsecond-wide pulse might). The timing PPS I've seen are in the >>> tens of milliseconds wide. If there is overshoot, perhaps a capacitor to >> >> Did you mean 10s of ns? The Sure width is about 5-10ns. at the card >> without any line attached. The line could certainly broaden that up to >> about 1us, but ms? >> Even the Garmin 18 is less than a usec. > > You're mistaking rise time for pulse width: Not the same thing at all! > > Some timing GPSs, like the original Oncore has a very short PPS > duration, while many/most others seem to be in the 100-200 ms range.
Who cares what the width is? It is the risetime that is important for timing. And it is the smearing of the risetime that messes up the timing. If the smearing is so bad that the pulse starts to loose its shape, you are totally screwed anyway. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
