[ntp:questions] Re: Reference clocks - which?

Tapio Sokura oh2kku at iki.fi
Sat Oct 30 08:23:27 UTC 2004


Richard B. Gilbert wrote:
> Tapio Sokura wrote:
>> and it is working fine with an average of 1-2 satellites tracked. When 
>> the position hold feature of the GPS receiver is used, one satellite 
>> is enough for timing. Of course more is better and more reliable, but 

> I wish I knew how to do that.  With NTP 4.2.0 at 1.1161-r the Oncore driver 
> seems to need 4 satellites in order to be "reachable"!  As a result, 
> mine works only about thirty percent of the time.   For whatever reason, 
> I get the best reception from about 9:00PM EDT to about 9:00AM.

The setup I'm using is running ntpd 4.1.1a at 1.791 on Linux 2.2.19-nano, I 
haven't bothered to update it for a while. I guess it is possible that 
there have been changes to the driver since that or maybe you are 
running a unit that doesn't have the position hold feature (I don't even 
know whether there are such Oncores)? My /etc/ntp.oncore.1 file looks 
like this:

MODE 1
LAT 60 3.1164
LON 24 30.2508
HT 28 M
DELAY 18 NS
CHAN 6
TRAIM NO
CLEAR

The relevant options here are MODE 1 and the three lines that follow it 
specifying the location used for position hold. I have disabled T-RAIM 
because the system seems to work better without it with only a couple of 
satellites visible. This is a home system so continuous reliability of 
the timing information is not that critical.

ntp.conf has these two lines for my Oncore VP:

pps /dev/oncore.pps.1 clear hardpps
server 127.127.30.1 prefer

   Tapio



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