[ntp:questions] Re: Reference clocks - which?
Richard B. Gilbert
rgilbert88 at comcast.net
Sat Oct 30 02:18:21 UTC 2004
Tapio Sokura wrote:
> Richard B. Gilbert wrote:
>> A Motorola Oncore M12+T GPS receiver is available from Synergy
>> Systems <http://www.synergy-gps.com/>
>> for around $200US. This is far better than what you say you need. It
> They also have used, but fully functional Oncore VPs for sale for
> something like 30-40 USD (see the excess inventory link on the front
> page). In addition to the GPS itself you need a suitable antenna and
> power supply along with 5 volt regulation and a max232 circuit for
> serial port level conversion.
> Anyway, a GPS synchronized time server can be built for considerably
> under 100 USD, not counting the PC itself. You just need to tinker a
> bit with the additional circuits and provide some kind of housing for
> them and the GPS board. The timing performance of Oncore VPs is
> excellent, generally the performance of the whole system is more
> limited by the PC than the GPS receiver.
>> requires that you be able site an antenna where it will have an
>> unobstructed view of the sky.
> I run my 6 channel Oncore VP with a magmount antenna located indoors
> 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
> you can make do with a quite limited view of the sky as well.
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.
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