On 2013-08-01, DaveB <[email protected]> wrote: > In article <[email protected]>, david- > [email protected] says... >> >> On 31/07/2013 20:36, DaveB wrote: >> [] >> > The server is using 5 'net based servers at this time (my original GPS >> > RX died) and is only just stable enough for what I'm doing. Sometimes >> > due to asymetric ping times, it "wanders a bit" for an hour or three. >> [] >> > Oh... Though the time server is FreeBSD based, other boxes in my empire >> > are a mixture of Windows and Linux, various versions types and >> > requirements. >> > >> > Cheers All. >> > >> > Dave. (G0WBX/G8KBV) >> >> Dave, >> >> A small GPS with PPS I can recommend to you is this one: >> >> http://www.adafruit.com/products/746 >> >> At least here, on the top floor of a two-storey house in Scotland, it >> gets enough signal to lock consistently. Not too expensive, and >> available from a UK stockist. >> >> >> http://proto-pic.co.uk/ultimate-gps-breakout-66-channel-w-10-hz-updates-mtk3339-chipset/ >> >> A few hundred microseconds should be enough for your pulse, although >> GPSs tend to use either 100 ms or 200 ms by default. Easier to see on a >> non-storage 'scope as well! I'm pondering on making a driver and having >> a terminated line running around the shack here (at pseudo RS-232 >> levels) for feeding PPS into all my PCs which have COM ports to get the >> best time synchronisation. AT the moment, those PCs which aren't >> stratum-1 have the poll interval set to 32 seconds to the local >> stratum-1 servers. >> >> I'm sure you know about the information on my site for FreeBSD, Windows >> and Linux, but others may not: >> >> http://www.satsignal.eu/ntp/index.html > > Yes, well aware of your wonderful resource pages. And thanks for the > link to the adafruit site, I'd forgotten about them. > > I now have a new-old-stock GPS-16 (with unmolested full length lead and > original connector) should I need, but I may end up using that for > similar needs in a mobile setting, hence my interest in using the TB to > drive the shack NTP box. > > Took a look at the TB's PPS signal last night, & yes, 20ns duration, and > though it can be turned -ve (as in 0 to -5V) or off, the width can't be > changed.
nanoseconds? That could easily get washed out by inappropriate termination or a cable with too high a load for the output drivers on the trimble (ev, 50 ohm cable, would require a steady state current of 100mA which is a lot I suspect that the voltages getting through are just too low to trigger the interrupt because of current saturation of the output. > > Too many toys, so little time. :) > > 73. > > Dave G0WBX/G8KBV. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
