Date: Wed, 19 May 1999 07:49:47 -0600 From: Wes Peters <wes@softweyr.com> To: Joe Abley <jabley@clear.co.nz> Cc: Matthew Dillon <dillon@apollo.backplane.com>, Joe McGuckin <joe@monk.via.net>, hackers@FreeBSD.ORG Subject: Re: GPS receivers for xntpd (off-topic) Message-ID: <3742C17B.9FC4FB96@softweyr.com> References: <199905190318.UAA06602@monk.via.net> <199905190602.XAA38227@apollo.backplane.com> <19990519220833.A99692@clear.co.nz>
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Joe Abley wrote: > > On Tue, May 18, 1999 at 11:02:38PM -0700, Matthew Dillon wrote: > > [various GPS chat] > > I have been meaning to do some research on this kind of stuff for a while. > We have GPS receivers in the machine room that supply clock for some of > the transmission network, but when I ask the telco guys about the output > of these receivers they just frown confusedly and say "it's a 2 meg clock". > I haven't mentioned NTP, because I can't be bothered to spell it for them :) > > So, we have an RF GPS source in the next rack which we can split and run > into our racks on coax. What kind of receiver do we need to provide a > synch source for xntpd to chime off? Just about any GPS receiver with serial output will do, depending on your absolute accuracy requirements. IIRC, with serial NMEA 0138 outputs, ntp sees an overall accuracy of +/- 120 usec. Most people can live with that. ;^) West Marine has a nice little Garmin handheld unit on sale for like $99 right now. If it has an external antenna jack, it would work as well as anything. You'll need to get +12v DC to it, as well as a serial line to your ntp server. As for mounting, I'd just wire- tie it to the rack. High-tech stuff, you know. http://www.garmin.com/ http://www.westmarine.com/ http://www.eecis.udel.edu/~ntp Happy surfing! -- "Where am I, and what am I doing in this handbasket?" Wes Peters Softweyr LLC http://www.softweyr.com/~softweyr wes@softweyr.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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