[ntp:questions] Thunderbolt at NTP ref clock.
Mark C. Stephens
marks at non-stop.com.au
Fri Aug 2 01:01:07 UTC 2013
You can control the thunderbolt PPS width with Lady Heather software:
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.
From: questions-bounces+marks=non-stop.com.au at lists.ntp.org [mailto:questions-bounces+marks=non-stop.com.au at lists.ntp.org] On Behalf Of DaveB
Sent: Friday, 2 August 2013 5:11 AM
To: questions at lists.ntp.org
Subject: Re: [ntp:questions] Thunderbolt at NTP ref clock.
In article <ktcujr$vpc$1 at dont-email.me>, david- taylor at blueyonder.co.uk.invalid 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)
> A small GPS with PPS I can recommend to you is this one:
> 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.
> 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
> 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:
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. :)
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