[ntp:questions] Re: Reference clocks questions

Richard B. Gilbert rgilbert88 at comcast.net
Mon Jul 3 18:01:34 UTC 2006

Julien wrote:

> Richard B. Gilbert a écrit :
>>The Garmin GPS18LVC is available for something like $85 US.  An Oncore
>>M12 timing receiver with evaluation circuit board, is available from
>>http://www.synergy-gps.com/ for around $200 US.  The Oncore used to be
> According to http://time.qnan.org/, the Garmin GPS18LVC looks fine to
> me, however I have a few concerns:
> 1/ I don't want to use my soldering iron. Anyone knows a reseller that
> provide something similar to the RS-232 interface at
> http://time.qnan.org/ ?
> 2/ My servers are shipped with RHEL3, which come with a 2.4
> pre-compiled Linux kernel and ntpd. I want to avoid any patching and
> compilation. What do I need to do to make ntpd read the PPS and the GPS
> time? Would the serial module (providing /dev/ttys*) and gpsd suffice?

You must either use your soldering iron or spend more money.  The 
Motorola Oncore that I mentioned was ordered with an evaluation circuit 
board and included an antenna, an RS232 cable, and a "universal" power 
supply.  That was $200 US.  You can just plug that in and it works.  The 
disadvantage is that it's a naked circuit board with no protective case.

For still more money, you get more; a metal case, built in power supply, 
  an NTP server and network interface, etc.  The more you pay the more 
you get.

For about $1100 US, Meinberg Funkuhren will sell you a GPS receiver on a 
PCI card that you can just plug into the computer.  Check their web site 
for the technical details; it looks to me like a very nice gadget but 
the price is a good deal more than I'm prepared to spend.

Symmetricom has a model BC637PCI which is a GPS disciplined crystal 
oscillator on a PCI card.  I believe that might cost as much as $3000 US.

If you contact the author of the web page http://time.qnan.org/ he might 
be willing to produce some of the interfaces he designed; what he has 
done is to provide a means to power the Garmin GPS receiver from a USB 
connector and you will still have to use a soldering iron to attach a 
DB-9 connector to the GPS receiver.

You will need to edit the ntp.conf file provided by Red Hat.  You will 
need to create links for the serial interface and the PPS output.  I'm 
not familiar with the details; I've never used the Garmin GPS.

If Red Hat does not distribute a very recent version of ntpd, you should 
probably install the latest and greatest from ntp.org.

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