[ntp:questions] Thunderbolt at NTP ref clock.

David Lord snews at lordynet.org
Thu Aug 1 23:48:20 UTC 2013


DaveB wrote:
> 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)
>> 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.
> 
> Too many toys, so little time. :)

Hi

a simple monostable can give an extended pulse long enough to
be caught by DCD on a serial port. Yes it causes a delay but
not likely to be more than a few us.

I've tried with parallel port using atom driver but could not
see  any difference other that I could use different pps source.


another David


> 
> 73.
> 
> Dave G0WBX/G8KBV.



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