Just an interesting observation. Last night, shortly after I wrote about
my dual GPSDO system, I decided to take a look at it, with the usual
scope setup looking at both 10 MHz outputs. It looked like one of those
reasonably good times, where the phase between them seemed very stable
during fai
Tom
Been following the thread with interest. I think several years ago it was
mentioned that LadyHeather could produce results by using a external 10 MHz
into a GPS reciver for its main oscillator. Always seemed like a great just
over the horizon project.
With respect to the uBlox F9. Lost me on th
JA, you mention using a Septentrio mosaic-T. I've not been able to
locate dev boards for the moasic-T (just the -X5 anf the -H).
Didi you build a board, or is there a -T dev board out there somewhere?
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I've been using the NetRS for timing for a couple of years now. They are
inexpensive and work well when properly configured, but they do have
their quirks. Some notes I've found useful:
1. The NetRS needs a dongle to provide primary power and the Ethernet
interface. Approximately 100% of the e
I've been working on frequency/stability measurements using the Trimble
NetRS and newer Mosaic-T dual-frequency receivers. Very early data
indicates that the NetRS does just about as well as the Mosaic, assuming
you are only interested in GPS and not GLONASS or the other
constellations the Mos
Skip Withrow's writeup is very interesting. As Skip mentioned, the Trimble
NetRS is a survey-grade dual frequency GPS receiver which accepts a 10 MHz
clock input.
It appears that the US Coast Guard has recently replaced a large number of
these NetRS units, and sent the old ones to surplus. They ar
> I've had the same question but I can't see how it could possibly "know"
> its own frequency error/uncertainty. What would it reference to?
That's why it's a rough internal *estimate*, not an actual measurement
against an external reference. Again, it goes back to how a GPSDO works.
There is t
On 3/7/22 9:48 AM, Krishna Makhija wrote:
Thanks Mattia. What did you use for your Layer 1? I need to place one of
the SDRs on a drone and one on the ground so a fiber or LAN cable is out. I
could use WLAN but can you get sub-nanosecond performance over wi-fi? My
initial guess would be no but I a
Hi,
You can definitely get sub-ns precision using a 4-8 MHz bandwidth wireless
protocol. You are not limited by the sampling period. In my previous work I
used 802.15.4-CSS (chirp based modulation), implemented by me in a SDR. The
sampling rate was 32 ns but with crosscorrelation and sample interpo
Hi
As soon as you put one device in motion relative to the other
and space them apart, the expected level of alignment between
the PPS outputs will drop. You are adding a number of variables
into the mix.
As noted in other posts, something like a F9T or a Mosiac T is
a much better way to do this
Thanks Mattia. What did you use for your Layer 1? I need to place one of
the SDRs on a drone and one on the ground so a fiber or LAN cable is out. I
could use WLAN but can you get sub-nanosecond performance over wi-fi? My
initial guess would be no but I am not certain.
Michael: I've had the same q
Looks like another wwvb remodulator has been built and a very nice writeup
by Doug. He also writes up issues of LED light interference and approaches
to solving that. Nice.
Link here
https://wa3dsp.org/spectracom_8170
The remodulator is a very simple way to make those old wwvb clocks work. It
is a
Hello,
When the GPS receiver (particularly talking about the ublox T series) is in
fixed time mode, I wonder about the sensitivity of PPS to the accuracy of
position given to the receiver. I have a pretty bad location for my GPS
antenna, so it cannot find a very accurate position (~10m at best, th
Hello Krishna,
what is your end application? How far away are those boards?
If each SDR can communicate to each other, you can run PTP over an ad-hoc
Layer 1.
I was able to get timestamps out of a 2.4 GHz chirp-based protocol with
less than 0.5ns RMS noise and two-way ranging error down to 10-20
ce
Hi Krishna,
> Hello Tom,
> Yes, the GPSDOs are working well. However, when I use each as a reference
> to a separate radio, I find there is a slow phase change over time
between
> said radios. I imagine this is expected since there will always be some
> error between two discrete oscillators.
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