[ntp:questions] Re: Reference clocks - which?
oh2kku at iki.fi
Fri Oct 29 23:05:09 UTC 2004
Richard B. Gilbert wrote:
> A Motorola Oncore M12+T GPS receiver is available from Synergy Systems
> 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.
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