You can control the thunderbolt PPS width with Lady Heather software: http://www.ke5fx.com/heather/readme.htm
Or build the TAPR fat PPS Pulse stretcher section on breadboard, not so complicated, just use the 1/2 of 74HC121 and a 74AC04 (or MAX232) to drive the serial port (or LPT port - less jitter) make sure any unused inputs are on the other 1/2 are tied to ground or pulled up to VCC. The circuit for the 74AC04 can be lifted from the output section of the TAPR PPS distribution amp (TADD-3). Or, you can use Just use the FATPPS circuit in its entirety - I built 3-in-1 custom PPS stretchers on one breadboard and it took me 1-2 hours. Please drop me an email if you need me to express this in a circuit. --marki -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of DaveB Sent: Friday, 2 August 2013 5:11 AM To: [email protected] Subject: Re: [ntp:questions] Thunderbolt at NTP ref clock. 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-update > s-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. Too many toys, so little time. :) 73. Dave G0WBX/G8KBV. _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
