[ntp:questions] Windows time question.

David J Taylor david-taylor at blueyonder.co.uk.invalid
Tue May 3 18:57:55 UTC 2011

> As the OP who started this (long and sometimes ammusing) thread...
> I do carry a GPS receiver with me, but sadly not PPS capable, I use it
> for location determination/tracking/navigating etc.   Maybe I should
> include a GPS18 or 16 in the already bulging Laptop bag I lug arround.

Even better if there were on on a USB stick, and you had a handy USB 
extension lead!

> In any case, with most hotel's now, you can't open the windows (the ones
> in the outside wall of the room, not the OS!) enough, to get anything
> sensible outside to get a decent view of the sky.   Many do not open at
> all, many are also now using "K Glass" that has a coating on it for
> thermal reasons, that appears to seriously attenuate GPS signals.

Yes, sometimes you're unlucky, but other times my GPS 60CSx does get a 

> I have also encountered problems many times with GPS RX's used for
> "normal satnav" purposes in the vicinity of some hotels, due I suspect
> to the *Huge* ammount of EM crap that seems to radiate from such
> establishments these days, in many, you cant even listen to FM radio in
> your room, let alone AM (or Shortwave for WWV etc!)  So much for EMC
> regs eh?

Not to mention power-line data transmission....

> Even mobile phone signals are heavily attenuated (or spoiled?) "in
> room", leaving only the expensive hotel wifi network (if it's working)
> as a comm's route out...   Not that mobile internet is any good for
> timekeeping!  I think from the latencies I sometime see, they use
> moonbounce to get back to base....

Free Wi-Fi is certainly one of my considerations now when choosing a 
hotel, and I've usually found that NTP works well enough over that.

> I have in one instance, had to use one of the "long range" BlueTooth
> adapters, to bt to a phone in the car, from a room (that luckily)
> overlooked the car park, to get any 'net conectivity.  Naff latency, but
> I got my work done!   I've also done the same trick, hoisting the phone
> some 50' up a mast in a plastic bag on a halyard (it was raining!) to
> get a signal on a remote customer site with no landline, then bt in
> remote sim mode to use the phone from the car!  And that was just for a
> voice call!

Never been that desperate!

> As earlier, the problem was a clash of interests between XP's own
> W32Time, and the National Instruments time discoverer/server, foisted on
> me by an update to other software (from our principle) that blindly and
> stupidly updates ALL of the NI installed tools and utilities, causing
> other problems too, not just the lockups.

Most tiresome.

> Now I've id'd the problem, I can work arround it.   But as earlier, the
> info about the pool servers and (perhaps) not needing the location tags
> was good to know, though from what else I read, it's debatable if it
> will work reliably and predicably in practice for a traveling laptop.
> Thanks for the info and insight peeps.
> Regards.
> DaveB

How critical is your time need?  If it's within minutes, then the PC's 
clock is likely good enough.  If it's in the UK or Europe, I would be 
surprised if pool servers did not get you well within the second - perhaps 
within 100msec - particularly if you set the servers based on the country 
you're in.  I suspect that if you need closer than tens of milliseconds, 
carrying round a GPS 18x LVC (which I jokingly suggested) may actually be 
necessary.  NTP was designed when connections were nothing like as good as 
they are now, and is supposedly robust in those circumstances.  It is 
designed for 24-hours operation, though.


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