Hi,
Very simple question: I noticed that my ubox8 module can produce a PPS-signal, not only at 1 pulse per second, but -apparently- up to 10
MHz.
Has anybody ever measured the quality of that signal (if locked to
the GNSS-signal) of a mass-market device like the ubox-8? Precision? Stability?
For my goal (a reference-signal for amateur-radio) it is probably
more then good enough, but -as a good technician- I like to be able
to put a figure on it.
I did a quick test with the hardware frequency-counter of my rigol,
and it reports a 3 to4 Hz difference at 10 MHz.
BTW. Does anybody have an idea how that signal is produced? I guess
is somewhere from the CDMA-decoding process.
I did a quick test with the hardware frequency-counter of my rigol,
and it reports a 3 to4 Hz difference at 10 MHz.
Unless they have analog steering of the local 10 MHz osc, they will be
off a little, 3-4 Hz seems fine. Some timing receivers will have a
TCXO or a Rb local osc, but not your ublox.
Terje
While running at 1Hz most PPS-equipped modules are capable of 15-35 ns
RMS, except that many of them are only capable of producing those pulses
at exact 10 MHz boundaries, i.e. it can be +/- 50 ns off.
The classic Motorola Oncore timing receiver would tell you, in the
serial message, exactly how far the last PPS signal was offset.
TerjeCheerio! Kr. Bonne.
Terje,
Just a small update.
On 25/10/18 09:46, Terje Mathisen wrote:
While running at 1Hz most PPS-equipped modules are capable of 15-35 ns
RMS, except that many of them are only capable of producing those
pulses at exact 10 MHz boundaries, i.e. it can be +/- 50 ns off.
The classic Motorola Oncore timing receiver would tell you, in the
serial message, exactly how far the last PPS signal was offset.
It turns out the ubox8 can also do that.
That information is in the NAV-TIME{GPS,GAL,GLO,BDS} messages. However,
the value is a unsigned integer, so I am not really sure how to
interprete it.
When I monitored it, the value was on one receiver around 20 ns, on
another one 10 ns. The good news is that on a second-to-second basis,
there is hardly any change: +/- 1 ns per second maximum.
So there is relative little drift on the clock.
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