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Re: cheap GPS

  • From: Jared Mauch
  • Date: Fri Aug 20 12:54:29 1999

	I'm interested in knowing if there are any telcos that
are using a GPS for their ckt timing, and this will cause that timing to
break, and those of us that take "clock source line" from M13's, etc..
will have problems with our channelized ckts (dial, ct3, etc..?)

	Anyone here privy to that type of information, and can
you comment?

	- jared

On Fri, Aug 20, 1999 at 09:42:30AM -0700, Jerry Scharf wrote:
> 
> 
> 
> On Fri, 20 Aug 1999, Alex P. Rudnev wrote:
> 
> > Through I did not see anything to worry about - your GPC may be show you 
> > the wrong date, but why it can affect the accuracy at all (except some 
> > short time around the very moment itself).
> > 
> 
> This is not true. There is things called the catelog and ephemerus, which
> are time based and give detailed corrections of the orbital position of
> the satellites that GPS derives locaton from. If the receiver does not
> handle rollover correctly, it will not correctly return time or position.
> Most receivers built since the mid 90s have handles this, and even more of
> the precision time sources have handled this, but nothing is perfect. It's
> really easy for the manufacturer to test this, but almost impossible for a
> user to (you need a GPS simulator.)
> 
> The good thing about modern NTP systems is that they don't accept times
> that are way off (there was a bad incident of a wacko clock many years
> ago) so if the GPS reports a 1980 date, the software would not believe it.
> That would mean losing synch with the GPS, but that should not be the end
> of time for a reasonalbly configured system.
> 
> I'll be watching all my clocks, but a lot of people won't be.

-- 
Jared Mauch  | pgp key available via finger from jared@puck.nether.net
clue++;      | http://puck.nether.net/~jared/  My statements are only mine.
             |           "Waste Management Consultant"           VOYN