alexandros kampolis wrote:
Most (if not all) use a GPS receiver as a precision time source. This
includes the NMEA messages and the 1 PPS output.
The question is: can i use the GPS receiver configuration but replace
the receiver with a precision 1 PPS source? I have a quartz frequency
standard that is able to output 1 PPS pulses and i want to use this
instead of the GPS receiver (which i do not have).
I'm asking this because i do not know if ntpd requires both the NMEA
messages and the 1 PPS pulses to work correct (or to work at all).
The precision xtal references do not have anywhere near the
long term accuracy of a GPS. The ovened modules I have
specifications for are a few ppb at best up to 100s of ppb.
You still also need a way of synchronising the PPS to exact
start of a second.
You can use ntp with PPS from a GPS and mark the seconds from
an internet source when you will obtain the same precision as
using NMEA to provide information as to what second. It is
the PPS pulse from the GPS that provides the precision so
using a precision frequency reference will not work. Some radio
signals, TDF and DCF, provide a seconds marker that is within a
few microseconds when receiver is close to the transmitter.
David
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