[ntp:questions] Re: Toggling time sync between two servers

Richard B. Gilbert rgilbert88 at comcast.net
Mon Mar 27 04:46:14 UTC 2006

vwvr6vw wrote:

> Thanks.  In this application, a few thousand dollars is not going to be
> an issue.  Having the correct time is critical and that is why I'm
> hoping that managment will go for it.  I believe the two sources we
> have now are from GPS.

Can you locate an antenna where it will have an unobstructed view of the 
entire sky?  If so, you can buy a GPS receiver (GARMIN GPL18LVC) for 
less than $100 and connect it to a serial port on a computer running 
ntpd with support for refclocks and presto!  It's a bit on the do it 
yourself side of things but it will get the job done.  You'll need a 
soldering iron, a DB9 connector, and a five volt power supply.

Moving upscale a bit, you can get a Motorola Oncore M12M timing receiver 
  (actually somebody else makes them now) from Synergy Systems.  You get 
the one with the evaluation board.  It's still pretty crude; a bare 
circuit board, but a power supply, antenna, and RS232 cable come with 
it. That will cost you $200.  Plug it in, connect it to a serial port, 
install ntpd, configure it, and go.

Moving pretty far upscale, you can get a box from Symmetricom with a 
built in GPS receiver and NTP server.  Plug it in to the AC outlet and 
your Ethernet.  I think these go for something like $2500 and up. 
That's about $2300 above my budget for toys so I don't have one and 
won't unless someone gives me one for Christmas.  I think that box may 
also come with an OCXO disciplined by the GPS to give some "holdover" 
capability if you lose signal from the satellites.

You can also get a box that gets the time from a CDMA Cell Phone base 
station (derived from GPS).  You plug that box into AC, your network and 
a whip antenna.  It, too, has a built-in NTP server.

You might want to get a couple of each.

More information about the questions mailing list