DW
drew wollin
Sun, Apr 27, 2025 8:52 AM
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guidehttps://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]https://portal.ga.gov.au/persona/pa
Geoscience Australia Portalhttps://portal.ga.gov.au/persona/pa
This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
portal.ga.gov.au
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<https://portal.ga.gov.au/persona/pa>
Geoscience Australia Portal<https://portal.ga.gov.au/persona/pa>
This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
portal.ga.gov.au
K
kb8tq@n1k.org
Sun, Apr 27, 2025 4:21 PM
Hi
Unfortunately there's a bit more to it than what the RTK stuff handles.
A quick simple / easy approach for this sort of thing is to do post
processing of RINEX files through one of the various outfits that does that
over the internet. Depending on where you live, that may be easier or less
easy to do.
A Trimble NetRS is an "oldie but goodie" way to get started.
Time out of a "conventional" GNSS receiver is subject to a lot of issues.
The post processing and the phase locked clock in the NetRS (plus the dual
band operation) get you started on taking care of them.
Bob
-----Original Message-----
From: drew wollin via time-nuts time-nuts@lists.febo.com
Sent: Sunday, April 27, 2025 4:52 AM
To: time-nuts@lists.febo.com
Cc: drew wollin drew_wollin@hotmail.com
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and
time.
Conventional GNSS receivers are accurate to a few metres and about 10
nanoseconds.
The accuracy can be improved by using correction information via RTK over
the internet. The receiver needs to be within about 20 km of an RTK base
station. The RTK base stations are linked and available as government or
private correction networks, some of which are free. See the link for the
Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's
effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm
accuracy positioning. U-blox and Quectel make RTK-capable receivers, which
are available from SparkFun and AliExpress. The receiver boards from
AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also
improves. Does anyone know if that is the case? I looked on the web without
success
The Quectel LG290P has a 1 PPS output that could be connected to other
timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS
receiver. I was thinking of replacing it with a 1 PPS signal from an
RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_v
iew/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_
view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]<https://docs.spar
kfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup
Guide<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/p
rint_view/>
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the
Quectel LG290P GNSS module. The board's dimensions, pin layout, and
connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA
Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The
board also accommodates users with a diverse choice of interfaces including
UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<https://portal
.ga.gov.au/persona/pa>
Geoscience Australia Portalhttps://portal.ga.gov.au/persona/pa
This portal (Geoscience Australia Portal Core) provides full access to
Geoscience Australia data and other publically available data sources as
well as suite of analytical and multi-criteria assessment tools to maximise
the value of the data. A series of personas have been created on the
Geoscience Australia Portal Core technology to meet specific stakeholder and
project requirements.
portal.ga.gov.au
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
Hi
Unfortunately there's a bit more to it than what the RTK stuff handles.
A quick simple / easy approach for this sort of thing is to do post
processing of RINEX files through one of the various outfits that does that
over the internet. Depending on where you live, that may be easier or less
easy to do.
A Trimble NetRS is an "oldie but goodie" way to get started.
Time out of a "conventional" GNSS receiver is subject to a lot of issues.
The post processing and the phase locked clock in the NetRS (plus the dual
band operation) get you started on taking care of them.
Bob
-----Original Message-----
From: drew wollin via time-nuts <time-nuts@lists.febo.com>
Sent: Sunday, April 27, 2025 4:52 AM
To: time-nuts@lists.febo.com
Cc: drew wollin <drew_wollin@hotmail.com>
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and
time.
Conventional GNSS receivers are accurate to a few metres and about 10
nanoseconds.
The accuracy can be improved by using correction information via RTK over
the internet. The receiver needs to be within about 20 km of an RTK base
station. The RTK base stations are linked and available as government or
private correction networks, some of which are free. See the link for the
Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's
effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm
accuracy positioning. U-blox and Quectel make RTK-capable receivers, which
are available from SparkFun and AliExpress. The receiver boards from
AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also
improves. Does anyone know if that is the case? I looked on the web without
success
The Quectel LG290P has a 1 PPS output that could be connected to other
timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS
receiver. I was thinking of replacing it with a 1 PPS signal from an
RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_v
iew/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_
view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]<https://docs.spar
kfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup
Guide<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/p
rint_view/>
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the
Quectel LG290P GNSS module. The board's dimensions, pin layout, and
connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA
Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The
board also accommodates users with a diverse choice of interfaces including
UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<https://portal
.ga.gov.au/persona/pa>
Geoscience Australia Portal<https://portal.ga.gov.au/persona/pa>
This portal (Geoscience Australia Portal Core) provides full access to
Geoscience Australia data and other publically available data sources as
well as suite of analytical and multi-criteria assessment tools to maximise
the value of the data. A series of personas have been created on the
Geoscience Australia Portal Core technology to meet specific stakeholder and
project requirements.
portal.ga.gov.au
_______________________________________________
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To unsubscribe send an email to time-nuts-leave@lists.febo.com
OP
Ole Petter Ronningen
Sun, Apr 27, 2025 6:46 PM
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency
and time.
Conventional GNSS receivers are accurate to a few metres and about 10
nanoseconds.
The accuracy can be improved by using correction information via RTK over
the internet. The receiver needs to be within about 20 km of an RTK base
station. The RTK base stations are linked and available as government or
private correction networks, some of which are free. See the link for the
Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's
effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm
accuracy positioning. U-blox and Quectel make RTK-capable receivers, which
are available from SparkFun and AliExpress. The receiver boards from
AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also
improves. Does anyone know if that is the case? I looked on the web without
success
The Quectel LG290P has a 1 PPS output that could be connected to other
timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS
receiver. I was thinking of replacing it with a 1 PPS signal from an
RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22
]<
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the
Quectel LG290P GNSS module. The board's dimensions, pin layout, and
connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA
Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The
board also accommodates users with a diverse choice of interfaces including
UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<
https://portal.ga.gov.au/persona/pa>
Geoscience Australia Portalhttps://portal.ga.gov.au/persona/pa
This portal (Geoscience Australia Portal Core) provides full access to
Geoscience Australia data and other publically available data sources as
well as suite of analytical and multi-criteria assessment tools to maximise
the value of the data. A series of personas have been created on the
Geoscience Australia Portal Core technology to meet specific stakeholder
and project requirements.
portal.ga.gov.au
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
Hi
As far as I know, the clocks cancel out in the RTK equations:
https://gssc.esa.int/navipedia/index.php?title=RTK_Fundamentals
Meaning; no better time from RTK itself.
BR
Ole
On Sun, Apr 27, 2025 at 6:09 PM drew wollin via time-nuts <
time-nuts@lists.febo.com> wrote:
> Hi All
>
> I have a long-term interest in GPS/GNSS for accurate position, frequency
> and time.
>
> Conventional GNSS receivers are accurate to a few metres and about 10
> nanoseconds.
>
> The accuracy can be improved by using correction information via RTK over
> the internet. The receiver needs to be within about 20 km of an RTK base
> station. The RTK base stations are linked and available as government or
> private correction networks, some of which are free. See the link for the
> Australian RTK network.
>
> The RTK corrections are based on local space weather and the ionosphere's
> effect on the received satellite signal.
>
> It is relatively inexpensive and easy to use these networks to get cm
> accuracy positioning. U-blox and Quectel make RTK-capable receivers, which
> are available from SparkFun and AliExpress. The receiver boards from
> AliExpress cost around US$50.
>
> The receivers can be used with software from the respective manufacturers
>
> With centimetre position accuracy, presumably, time pulse accuracy also
> improves. Does anyone know if that is the case? I looked on the web without
> success
>
> The Quectel LG290P has a 1 PPS output that could be connected to other
> timing equipment.
>
> I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS
> receiver. I was thinking of replacing it with a 1 PPS signal from an
> RTK-corrected LG290P.
>
> The other question, of course, is how do I measure if the time is better?
>
> Regards Drew VK4ZXI
>
> https://portal.ga.gov.au/persona/pa
>
>
> https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
> [
> https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22
> ]<
> https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
> >
> Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide<
> https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
> >
> The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the
> Quectel LG290P GNSS module. The board's dimensions, pin layout, and
> connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA
> Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The
> board also accommodates users with a diverse choice of interfaces including
> UART, SPI 1, and I 2 C 1.
> docs.sparkfun.com
>
> [https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<
> https://portal.ga.gov.au/persona/pa>
> Geoscience Australia Portal<https://portal.ga.gov.au/persona/pa>
> This portal (Geoscience Australia Portal Core) provides full access to
> Geoscience Australia data and other publically available data sources as
> well as suite of analytical and multi-criteria assessment tools to maximise
> the value of the data. A series of personas have been created on the
> Geoscience Australia Portal Core technology to meet specific stakeholder
> and project requirements.
> portal.ga.gov.au
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
>
EM
Ed Marciniak
Sun, Apr 27, 2025 6:47 PM
The PRS-10 documentation specifies a 2E-12 tuning step on the 22 bit DAC. While it does have a PPS input, whether it is useful to you, or at least directly so, depends on the use case.
From: Bob Camp via time-nuts time-nuts@lists.febo.com
Sent: Sunday, April 27, 2025 11:21:36 AM
To: 'Discussion of precise time and frequency measurement' time-nuts@lists.febo.com
Cc: kb8tq@n1k.org kb8tq@n1k.org
Subject: [time-nuts] Re: Does cm accurate GPS via RTK give more accurate time?
Hi
Unfortunately there's a bit more to it than what the RTK stuff handles.
A quick simple / easy approach for this sort of thing is to do post
processing of RINEX files through one of the various outfits that does that
over the internet. Depending on where you live, that may be easier or less
easy to do.
A Trimble NetRS is an "oldie but goodie" way to get started.
Time out of a "conventional" GNSS receiver is subject to a lot of issues.
The post processing and the phase locked clock in the NetRS (plus the dual
band operation) get you started on taking care of them.
Bob
-----Original Message-----
From: drew wollin via time-nuts time-nuts@lists.febo.com
Sent: Sunday, April 27, 2025 4:52 AM
To: time-nuts@lists.febo.com
Cc: drew wollin drew_wollin@hotmail.com
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and
time.
Conventional GNSS receivers are accurate to a few metres and about 10
nanoseconds.
The accuracy can be improved by using correction information via RTK over
the internet. The receiver needs to be within about 20 km of an RTK base
station. The RTK base stations are linked and available as government or
private correction networks, some of which are free. See the link for the
Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's
effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm
accuracy positioning. U-blox and Quectel make RTK-capable receivers, which
are available from SparkFun and AliExpress. The receiver boards from
AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also
improves. Does anyone know if that is the case? I looked on the web without
success
The Quectel LG290P has a 1 PPS output that could be connected to other
timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS
receiver. I was thinking of replacing it with a 1 PPS signal from an
RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://urldefense.proofpoint.com/v2/url?u=https-3A__portal.ga.gov.au_persona_pa&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=fo2M7gH4TwKd3LIbc7PphqdDUbqqO6A7-1nehL0BmNY&e=
https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fv&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=ZiUoeWM8jlrFekOS1shi6jKwhox6NBqWS_aS0AnOuXk&e=
iew/
[https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5F&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=V1SSVsb-CuViTYxxdkk-YU8TH-7W-hZfCkKCRyK8WSw&e=
view/%22https://urldefense.proofpoint.com/v2/url?u=https-3A__i.ytimg.com_vi_a-2DaU4-2DYodzg_default.jpg-2522&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=z-jLr9xGA6vql-rgBDV3EZ1Wbk0OgwwXRvvQSbOUYZY&e=]https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=tL7wgrNAFxbixU8WxbvlD1dNbrCXji7eRQwrbqAXxpk&e=
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup
Guidehttps://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=tL7wgrNAFxbixU8WxbvlD1dNbrCXji7eRQwrbqAXxpk&e=
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the
Quectel LG290P GNSS module. The board's dimensions, pin layout, and
connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA
Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The
board also accommodates users with a diverse choice of interfaces including
UART, SPI 1, and I 2 C 1.
https://urldefense.proofpoint.com/v2/url?u=http-3A__docs.sparkfun.com&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=gZVLp145dfe-S-uYy3tLslBaLQjxxcCIevPipgikWfo&e=
[https://urldefense.proofpoint.com/v2/url?u=https-3A__nonprod.portal.ga.gov.au_cache_images_portal-5Fga.png&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=m3sD3Pzcd8561SQ9TEJqUH8Qc_gnKAY4cK7VSCDchAg&e=]https://urldefense.proofpoint.com/v2/url?u=https-3A__portal.ga.gov.au_persona_pa&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=fo2M7gH4TwKd3LIbc7PphqdDUbqqO6A7-1nehL0BmNY&e=
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The PRS-10 documentation specifies a 2E-12 tuning step on the 22 bit DAC. While it does have a PPS input, whether it is useful to you, or at least directly so, depends on the use case.
________________________________
From: Bob Camp via time-nuts <time-nuts@lists.febo.com>
Sent: Sunday, April 27, 2025 11:21:36 AM
To: 'Discussion of precise time and frequency measurement' <time-nuts@lists.febo.com>
Cc: kb8tq@n1k.org <kb8tq@n1k.org>
Subject: [time-nuts] Re: Does cm accurate GPS via RTK give more accurate time?
Hi
Unfortunately there's a bit more to it than what the RTK stuff handles.
A quick simple / easy approach for this sort of thing is to do post
processing of RINEX files through one of the various outfits that does that
over the internet. Depending on where you live, that may be easier or less
easy to do.
A Trimble NetRS is an "oldie but goodie" way to get started.
Time out of a "conventional" GNSS receiver is subject to a lot of issues.
The post processing and the phase locked clock in the NetRS (plus the dual
band operation) get you started on taking care of them.
Bob
-----Original Message-----
From: drew wollin via time-nuts <time-nuts@lists.febo.com>
Sent: Sunday, April 27, 2025 4:52 AM
To: time-nuts@lists.febo.com
Cc: drew wollin <drew_wollin@hotmail.com>
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and
time.
Conventional GNSS receivers are accurate to a few metres and about 10
nanoseconds.
The accuracy can be improved by using correction information via RTK over
the internet. The receiver needs to be within about 20 km of an RTK base
station. The RTK base stations are linked and available as government or
private correction networks, some of which are free. See the link for the
Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's
effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm
accuracy positioning. U-blox and Quectel make RTK-capable receivers, which
are available from SparkFun and AliExpress. The receiver boards from
AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also
improves. Does anyone know if that is the case? I looked on the web without
success
The Quectel LG290P has a 1 PPS output that could be connected to other
timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS
receiver. I was thinking of replacing it with a 1 PPS signal from an
RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://urldefense.proofpoint.com/v2/url?u=https-3A__portal.ga.gov.au_persona_pa&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=fo2M7gH4TwKd3LIbc7PphqdDUbqqO6A7-1nehL0BmNY&e=
https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fv&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=ZiUoeWM8jlrFekOS1shi6jKwhox6NBqWS_aS0AnOuXk&e=
iew/
[https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5F&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=V1SSVsb-CuViTYxxdkk-YU8TH-7W-hZfCkKCRyK8WSw&e=
view/%22https://urldefense.proofpoint.com/v2/url?u=https-3A__i.ytimg.com_vi_a-2DaU4-2DYodzg_default.jpg-2522&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=z-jLr9xGA6vql-rgBDV3EZ1Wbk0OgwwXRvvQSbOUYZY&e=]<https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=tL7wgrNAFxbixU8WxbvlD1dNbrCXji7eRQwrbqAXxpk&e=>
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup
Guide<https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=tL7wgrNAFxbixU8WxbvlD1dNbrCXji7eRQwrbqAXxpk&e=>
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the
Quectel LG290P GNSS module. The board's dimensions, pin layout, and
connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA
Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The
board also accommodates users with a diverse choice of interfaces including
UART, SPI 1, and I 2 C 1.
https://urldefense.proofpoint.com/v2/url?u=http-3A__docs.sparkfun.com&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=gZVLp145dfe-S-uYy3tLslBaLQjxxcCIevPipgikWfo&e=
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This portal (Geoscience Australia Portal Core) provides full access to
Geoscience Australia data and other publically available data sources as
well as suite of analytical and multi-criteria assessment tools to maximise
the value of the data. A series of personas have been created on the
Geoscience Australia Portal Core technology to meet specific stakeholder and
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https://urldefense.proofpoint.com/v2/url?u=http-3A__portal.ga.gov.au&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=dEdkBl-tYnXggwepvoBwfhZ32U6v4M2GLsF5bPjB8JTAFXW51N_g0DbPOElge6AZ&s=LSC1aeU1k3kcRF-I82F-VhWtmNdiwrjV1VhVf954C5o&e=
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DC
David Cureton
Sun, Apr 27, 2025 10:22 PM
Hi Drew,
As you probably aware the posittion accurace is largely dependent on time accuracy. The largest error for domestic GPS recievers has been ionspheric variation in path from satellites to receiver as I understand. The new crop of cm accurate GPS's achive this step up in accuracy by using a second L5 Band and with the two frequencies in use, the ionsespheric variation can largely be modeled and compensated for by the reciever. Therefore you would also expect a similar step up in the performance of the timekeeping of these GPS's. I did have a quick loook at the ZED-F9P from ublox and the datasheets were devoid of ANY characterisation of the TIMEPULSE signal accuracy. However the receiver will also be limited by the internal reference clocks their timebase and the stability/phasen noise of the PLLs. I think there is a version of the Ublox devices that you can actually provide the recever with a timebase that is much better that the tiny little TCXO that is on the devices.
Look forward to hearing of your results.
Regards,
David VK3DCU
----- Original Message -----
From: "drew wollin via time-nuts" time-nuts@lists.febo.com
To: "time-nuts" time-nuts@lists.febo.com
Cc: "drew wollin" drew_wollin@hotmail.com
Sent: Sunday, 27 April, 2025 6:52:12 PM
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guidehttps://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
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This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
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Hi Drew,
As you probably aware the posittion accurace is largely dependent on time accuracy. The largest error for domestic GPS recievers has been ionspheric variation in path from satellites to receiver as I understand. The new crop of cm accurate GPS's achive this step up in accuracy by using a second L5 Band and with the two frequencies in use, the ionsespheric variation can largely be modeled and compensated for by the reciever. Therefore you would also expect a similar step up in the performance of the timekeeping of these GPS's. I did have a quick loook at the ZED-F9P from ublox and the datasheets were devoid of ANY characterisation of the TIMEPULSE signal accuracy. However the receiver will also be limited by the internal reference clocks their timebase and the stability/phasen noise of the PLLs. I think there is a version of the Ublox devices that you can actually provide the recever with a timebase that is much better that the tiny little TCXO that is on the devices.
Look forward to hearing of your results.
Regards,
David VK3DCU
----- Original Message -----
From: "drew wollin via time-nuts" <time-nuts@lists.febo.com>
To: "time-nuts" <time-nuts@lists.febo.com>
Cc: "drew wollin" <drew_wollin@hotmail.com>
Sent: Sunday, 27 April, 2025 6:52:12 PM
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<https://portal.ga.gov.au/persona/pa>
Geoscience Australia Portal<https://portal.ga.gov.au/persona/pa>
This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
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PK
Poul-Henning Kamp
Mon, Apr 28, 2025 9:08 AM
Ed Marciniak via time-nuts writes:
The PRS-10 documentation specifies a 2E-12 tuning step on the 22 bit DAC. While it does have a PPS input, whether it is useful to you, or at least directly so, depends on the use case.
I dont know if they have changed it, but it used to be two 12 bit DAC's in tandem.
At least on my PRS10 there were visible discontinuities when the upper DAC stepped.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
--------
Ed Marciniak via time-nuts writes:
> The PRS-10 documentation specifies a 2E-12 tuning step on the 22 bit DAC. While it does have a PPS input, whether it is useful to you, or at least directly so, depends on the use case.
I dont know if they have changed it, but it used to be two 12 bit DAC's in tandem.
At least on my PRS10 there were visible discontinuities when the upper DAC stepped.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
PK
Pavel Kořenský
Mon, Apr 28, 2025 10:48 AM
Hello,
I just wanted to share that u-blox also makes the F9T module (the "T"
stands for "timing," I believe), which is generally even more precise
than the F9P. SparkFun has a board based on it here:
https://www.sparkfun.com/sparkfun-gnss-timing-breakout-zed-f9t-qwiic.html
The board isn't cheap, but according to the datasheet, the F9T offers an
absolute timing accuracy of 5 ns (1-sigma, fixed position mode),
depending on things like temperature, atmospheric conditions, baseline
length, GNSS antenna quality, multipath, satellite visibility, and
geometry. In differential timing mode, the accuracy can go down to 2.5 ns.
I'm currently using this module in my prototype GPSDO based on a cesium
clock, and so far, the results have been very good. I'm not using the
standard 1PPS output — instead, I use a programmable output from the GPS
receiver set to 1.25 MHz, and I feed it into a PLL with a Kalman filter
at the input.
Now, regarding how to measure which clock is "better": that's a tough
question. If you have only two clocks, you can't really tell which one
is more accurate — you need a third, better reference. Ideally, that
would be a cesium standard or, even better, a hydrogen maser.
Unfortunately, getting access to something like that is very difficult
for a home lab.
What I did was use my rubidium (Rb) standard as a reference and measured
my GPS-PLL design disciplining an old, reliable HP10811 crystal
oscillator. Later, I used the same setup to stabilize the Rb oscillator
and compared it against a commercial GPSDO. I'm still hoping to get
access to a cesium clock in the future (as far as I know, there's no
hydrogen maser available in Prague or anywhere in the Czech Republic).
The main reason I haven’t published my design yet is that I haven't been
able to make a full comparison against a top-tier reference clock.
Best regards,
PavelK
Dne 27.04.2025 v 10:52 drew wollin via time-nuts napsal(a):
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guidehttps://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
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Hello,
I just wanted to share that u-blox also makes the F9T module (the "T"
stands for "timing," I believe), which is generally even more precise
than the F9P. SparkFun has a board based on it here:
https://www.sparkfun.com/sparkfun-gnss-timing-breakout-zed-f9t-qwiic.html
The board isn't cheap, but according to the datasheet, the F9T offers an
absolute timing accuracy of 5 ns (1-sigma, fixed position mode),
depending on things like temperature, atmospheric conditions, baseline
length, GNSS antenna quality, multipath, satellite visibility, and
geometry. In differential timing mode, the accuracy can go down to 2.5 ns.
I'm currently using this module in my prototype GPSDO based on a cesium
clock, and so far, the results have been very good. I'm not using the
standard 1PPS output — instead, I use a programmable output from the GPS
receiver set to 1.25 MHz, and I feed it into a PLL with a Kalman filter
at the input.
Now, regarding how to measure which clock is "better": that's a tough
question. If you have only two clocks, you can't really tell which one
is more accurate — you need a third, better reference. Ideally, that
would be a cesium standard or, even better, a hydrogen maser.
Unfortunately, getting access to something like that is very difficult
for a home lab.
What I did was use my rubidium (Rb) standard as a reference and measured
my GPS-PLL design disciplining an old, reliable HP10811 crystal
oscillator. Later, I used the same setup to stabilize the Rb oscillator
and compared it against a commercial GPSDO. I'm still hoping to get
access to a cesium clock in the future (as far as I know, there's no
hydrogen maser available in Prague or anywhere in the Czech Republic).
The main reason I haven’t published my design yet is that I haven't been
able to make a full comparison against a top-tier reference clock.
Best regards,
PavelK
Dne 27.04.2025 v 10:52 drew wollin via time-nuts napsal(a):
> Hi All
>
> I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
>
> Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
>
> The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
>
> The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
>
> It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
>
> The receivers can be used with software from the respective manufacturers
>
> With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
>
> The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
>
> I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
>
> The other question, of course, is how do I measure if the time is better?
>
> Regards Drew VK4ZXI
>
> https://portal.ga.gov.au/persona/pa
>
> https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
> [https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
> Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
> The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
> docs.sparkfun.com
>
> [https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<https://portal.ga.gov.au/persona/pa>
> Geoscience Australia Portal<https://portal.ga.gov.au/persona/pa>
> This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
> portal.ga.gov.au
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
> To unsubscribe send an email to time-nuts-leave@lists.febo.com
BC
Bob Camp
Mon, Apr 28, 2025 2:00 PM
Hi
If you want a GNSS device for good timing, you need to get a version that is designed for that. Is it a design difference or just a firmware change? You never really know. Either way, you get features you need in the timing version. Usually some or all of them are missing in a version that is not timing focused.
In the uBlox world you go to a F10T or an F9T to get the timing stuff. In the Septentrio universe you head over to the Mosiac-T. Those are all multi-band devices. You can get any of them as “demo kits” from the manufacturer. You can also get them (sometimes for less money) built into boards from various outfits. The older single band stuff is still very much out there as well. The uBlox single band versions follow the same “T on the end” designators. They do have a few that don’t quite fit that though.,
Only having L1 / L5 gets you going. That’s how uBlox seems to be headed. Most of the RINEX processing folks are still on L1 / L2. I prefer the Mosiac-T for several reasons. One of them is that it will cover L2. (along with everything else). It also will lock up to an external 10 MHz source which makes a lot of things easier. RINEX post processing is useful, you may need to wait for a couple of weeks to get a “full up correct” solution though. Very much not real time. Still a great way to check things. If you really decide go crazy, the Mosaic-T has a real time timing correction service you can subscribe to.
Accuracy wise, a single band device is stuck with those atmospheric issues running real time. Is that a 10 ns swing today and a 50 ns swing tomorrow? It easily could be. Any module without sawtooth correction will have an uncorrectable jitter on the PPS output. Numbers in the 10 to 20 ns range are not at all uncommon. All of that is on top of whatever the errors are in the “timing solution” on the device. How does all that line up with those top of page bold print claims? …. there’s always footnotes :) :)
We’re not quite done yet in terms of accuracy. The number any module gives you will (without some sort of fancy correction setup) be relative to the GNSS system time. Depending on the GNSS system there will be somewhat better or not quite as good correlation between GNSS system time and this or that ground based timescale. Is that X ns or Y ns? It very much depends which one and how things are going.
Still not quite done though. Time at the ns level is a bit exciting. BIH in Paris works out what the time was after the fact. Yes the various standard organizations around the world do try to stay on time. Welcome to another set of is it X or is it Y ns off numbers. You’ll know in a month or two …
No, that’s not the whole story. It’s just a quick run past a few of the highlights. It ignores a number of rabbit holes you could (and might) run down here or there. There’s a lot of math / numbers you could dive into, even on what is discussed here.
Fun !!
Bob
On Apr 27, 2025, at 6:22 PM, David Cureton via time-nuts time-nuts@lists.febo.com wrote:
Hi Drew,
As you probably aware the posittion accurace is largely dependent on time accuracy. The largest error for domestic GPS recievers has been ionspheric variation in path from satellites to receiver as I understand. The new crop of cm accurate GPS's achive this step up in accuracy by using a second L5 Band and with the two frequencies in use, the ionsespheric variation can largely be modeled and compensated for by the reciever. Therefore you would also expect a similar step up in the performance of the timekeeping of these GPS's. I did have a quick loook at the ZED-F9P from ublox and the datasheets were devoid of ANY characterisation of the TIMEPULSE signal accuracy. However the receiver will also be limited by the internal reference clocks their timebase and the stability/phasen noise of the PLLs. I think there is a version of the Ublox devices that you can actually provide the recever with a timebase that is much better that the tiny little TCXO that is on the devices.
Look forward to hearing of your results.
Regards,
David VK3DCU
----- Original Message -----
From: "drew wollin via time-nuts" time-nuts@lists.febo.com
To: "time-nuts" time-nuts@lists.febo.com
Cc: "drew wollin" drew_wollin@hotmail.com
Sent: Sunday, 27 April, 2025 6:52:12 PM
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guidehttps://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]https://portal.ga.gov.au/persona/pa
Geoscience Australia Portalhttps://portal.ga.gov.au/persona/pa
This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
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Hi
If you want a GNSS device for good timing, you need to get a version that is designed for that. Is it a design difference or just a firmware change? You never really know. Either way, you get features you need in the timing version. Usually some or all of them are missing in a version that is not timing focused.
In the uBlox world you go to a F10T or an F9T to get the timing stuff. In the Septentrio universe you head over to the Mosiac-T. Those are all multi-band devices. You can get any of them as “demo kits” from the manufacturer. You can also get them (sometimes for less money) built into boards from various outfits. The older single band stuff is still very much out there as well. The uBlox single band versions follow the same “T on the end” designators. They do have a few that don’t quite fit that though.,
Only having L1 / L5 gets you going. That’s how uBlox seems to be headed. Most of the RINEX processing folks are still on L1 / L2. I prefer the Mosiac-T for several reasons. One of them is that it will cover L2. (along with everything else). It also will lock up to an external 10 MHz source which makes a lot of things easier. RINEX post processing is useful, you may need to wait for a couple of weeks to get a “full up correct” solution though. Very much not real time. Still a great way to check things. If you really decide go crazy, the Mosaic-T has a real time timing correction service you can subscribe to.
Accuracy wise, a single band device is stuck with those atmospheric issues running real time. Is that a 10 ns swing today and a 50 ns swing tomorrow? It easily could be. Any module without sawtooth correction will have an uncorrectable jitter on the PPS output. Numbers in the 10 to 20 ns range are not at all uncommon. All of that is on top of whatever the errors are in the “timing solution” on the device. How does all that line up with those top of page bold print claims? …. there’s always footnotes :) :)
We’re not quite done yet in terms of accuracy. The number any module gives you will (without some sort of fancy correction setup) be relative to the GNSS system time. Depending on the GNSS system there will be somewhat better or not quite as good correlation between GNSS system time and this or that ground based timescale. Is that X ns or Y ns? It very much depends which one and how things are going.
Still not quite done though. Time at the ns level is a bit exciting. BIH in Paris works out what the time was after the fact. Yes the various standard organizations around the world do try to stay on time. Welcome to another set of is it X or is it Y ns off numbers. You’ll know in a month or two …
No, that’s not the whole story. It’s just a quick run past a few of the highlights. It ignores a number of rabbit holes you could (and might) run down here or there. There’s a lot of math / numbers you could dive into, even on what is discussed here.
Fun !!
Bob
> On Apr 27, 2025, at 6:22 PM, David Cureton via time-nuts <time-nuts@lists.febo.com> wrote:
>
>
> Hi Drew,
> As you probably aware the posittion accurace is largely dependent on time accuracy. The largest error for domestic GPS recievers has been ionspheric variation in path from satellites to receiver as I understand. The new crop of cm accurate GPS's achive this step up in accuracy by using a second L5 Band and with the two frequencies in use, the ionsespheric variation can largely be modeled and compensated for by the reciever. Therefore you would also expect a similar step up in the performance of the timekeeping of these GPS's. I did have a quick loook at the ZED-F9P from ublox and the datasheets were devoid of ANY characterisation of the TIMEPULSE signal accuracy. However the receiver will also be limited by the internal reference clocks their timebase and the stability/phasen noise of the PLLs. I think there is a version of the Ublox devices that you can actually provide the recever with a timebase that is much better that the tiny little TCXO that is on the devices.
>
>
> Look forward to hearing of your results.
>
>
> Regards,
>
> David VK3DCU
>
> ----- Original Message -----
> From: "drew wollin via time-nuts" <time-nuts@lists.febo.com>
> To: "time-nuts" <time-nuts@lists.febo.com>
> Cc: "drew wollin" <drew_wollin@hotmail.com>
> Sent: Sunday, 27 April, 2025 6:52:12 PM
> Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
>
> Hi All
>
> I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
>
> Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
>
> The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
>
> The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
>
> It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
>
> The receivers can be used with software from the respective manufacturers
>
> With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
>
> The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
>
> I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
>
> The other question, of course, is how do I measure if the time is better?
>
> Regards Drew VK4ZXI
>
> https://portal.ga.gov.au/persona/pa
>
> https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
> [https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
> Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide<https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/>
> The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
> docs.sparkfun.com
>
> [https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]<https://portal.ga.gov.au/persona/pa>
> Geoscience Australia Portal<https://portal.ga.gov.au/persona/pa>
> This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
> portal.ga.gov.au
>
> _______________________________________________
> time-nuts mailing list -- time-nuts@lists.febo.com
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Ed Marciniak
Mon, Apr 28, 2025 4:16 PM
The LEA-M8F is the uBlox you’re referring to.
It features a 30.72 MHz VCXO that is steered to a clock bias of zero. The pulse per second is derived from a clock edge. (This is per their documentation).
It has been said that the phase noise of the 30.72 MHz source isn’t very impressive.
My gut says that phase locking a very high quality 10MHz ovenized oscillator with millihertz loop bandwidth is about as clean as you’ll get without spending thousands.
For what it’s worth, the M8F would be single band. There isn’t a 9 or 10 series frequency module.
The unicore timing module UT-982 doesn't specify how they get their 5ns one sigma specification for PPS.
For currently produced components or modules under 1500 USD, there is the LEA-M8F(single band), a couple part numbers from Furuno (all single band I think), and the Septentrio Mosiac-T for options that steer a clock rather than merely provide a PPS.
From time to time, I think the NetRS also comes up.
If anyone is aware of one I've left out, please do share.
From: David Cureton via time-nuts time-nuts@lists.febo.com
Sent: Sunday, April 27, 2025 5:22:05 PM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: drew wollin drew_wollin@hotmail.com; David Cureton david.cureton@ceos.com.au
Subject: [time-nuts] Re: Does cm accurate GPS via RTK give more accurate time?
Hi Drew,
As you probably aware the posittion accurace is largely dependent on time accuracy. The largest error for domestic GPS recievers has been ionspheric variation in path from satellites to receiver as I understand. The new crop of cm accurate GPS's achive this step up in accuracy by using a second L5 Band and with the two frequencies in use, the ionsespheric variation can largely be modeled and compensated for by the reciever. Therefore you would also expect a similar step up in the performance of the timekeeping of these GPS's. I did have a quick loook at the ZED-F9P from ublox and the datasheets were devoid of ANY characterisation of the TIMEPULSE signal accuracy. However the receiver will also be limited by the internal reference clocks their timebase and the stability/phasen noise of the PLLs. I think there is a version of the Ublox devices that you can actually provide the recever with a timebase that is much better that the tiny little TCXO that is on the devices.
Look forward to hearing of your results.
Regards,
David VK3DCU
----- Original Message -----
From: "drew wollin via time-nuts" time-nuts@lists.febo.com
To: "time-nuts" time-nuts@lists.febo.com
Cc: "drew wollin" drew_wollin@hotmail.com
Sent: Sunday, 27 April, 2025 6:52:12 PM
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://urldefense.proofpoint.com/v2/url?u=https-3A__portal.ga.gov.au_persona_pa&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=cZIjH_KYX5_apw_8MtAHQGgQO4hHZNsXHy3jb-f6A5bP6jiYYgAzmk2STFkeQsuG&s=bI1-Gq0mn6f5DWcF5f7u73fHEPPrqrbolWEisUWYdu0&e=
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Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guidehttps://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=cZIjH_KYX5_apw_8MtAHQGgQO4hHZNsXHy3jb-f6A5bP6jiYYgAzmk2STFkeQsuG&s=nYsJAWKWyYZ8VFcYDuhaIDLn8gsHUK_b8-xYaWdAmjY&e=
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
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The LEA-M8F is the uBlox you’re referring to.
It features a 30.72 MHz VCXO that is steered to a clock bias of zero. The pulse per second is derived from a clock edge. (This is per their documentation).
It has been said that the phase noise of the 30.72 MHz source isn’t very impressive.
My gut says that phase locking a very high quality 10MHz ovenized oscillator with millihertz loop bandwidth is about as clean as you’ll get without spending thousands.
For what it’s worth, the M8F would be single band. There isn’t a 9 or 10 series frequency module.
The unicore timing module UT-982 doesn't specify how they get their 5ns one sigma specification for PPS.
For currently produced components or modules under 1500 USD, there is the LEA-M8F(single band), a couple part numbers from Furuno (all single band I think), and the Septentrio Mosiac-T for options that steer a clock rather than merely provide a PPS.
From time to time, I think the NetRS also comes up.
If anyone is aware of one I've left out, please do share.
________________________________
From: David Cureton via time-nuts <time-nuts@lists.febo.com>
Sent: Sunday, April 27, 2025 5:22:05 PM
To: Discussion of precise time and frequency measurement <time-nuts@lists.febo.com>
Cc: drew wollin <drew_wollin@hotmail.com>; David Cureton <david.cureton@ceos.com.au>
Subject: [time-nuts] Re: Does cm accurate GPS via RTK give more accurate time?
Hi Drew,
As you probably aware the posittion accurace is largely dependent on time accuracy. The largest error for domestic GPS recievers has been ionspheric variation in path from satellites to receiver as I understand. The new crop of cm accurate GPS's achive this step up in accuracy by using a second L5 Band and with the two frequencies in use, the ionsespheric variation can largely be modeled and compensated for by the reciever. Therefore you would also expect a similar step up in the performance of the timekeeping of these GPS's. I did have a quick loook at the ZED-F9P from ublox and the datasheets were devoid of ANY characterisation of the TIMEPULSE signal accuracy. However the receiver will also be limited by the internal reference clocks their timebase and the stability/phasen noise of the PLLs. I think there is a version of the Ublox devices that you can actually provide the recever with a timebase that is much better that the tiny little TCXO that is on the devices.
Look forward to hearing of your results.
Regards,
David VK3DCU
----- Original Message -----
From: "drew wollin via time-nuts" <time-nuts@lists.febo.com>
To: "time-nuts" <time-nuts@lists.febo.com>
Cc: "drew wollin" <drew_wollin@hotmail.com>
Sent: Sunday, 27 April, 2025 6:52:12 PM
Subject: [time-nuts] Does cm accurate GPS via RTK give more accurate time?
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
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[https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_-2522https-3A__i.ytimg.com_vi_a-2DaU4-2DYodzg_default.jpg-2522&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=cZIjH_KYX5_apw_8MtAHQGgQO4hHZNsXHy3jb-f6A5bP6jiYYgAzmk2STFkeQsuG&s=Pp4SZoSbNSxsNkw9pBHm1e-Cj4dhTGwTA3yXIu_jxoQ&e=]<https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=cZIjH_KYX5_apw_8MtAHQGgQO4hHZNsXHy3jb-f6A5bP6jiYYgAzmk2STFkeQsuG&s=nYsJAWKWyYZ8VFcYDuhaIDLn8gsHUK_b8-xYaWdAmjY&e=>
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide<https://urldefense.proofpoint.com/v2/url?u=https-3A__docs.sparkfun.com_SparkFun-5FLG290P-5FQuadband-5FGNSS-5FRTK-5FBreakout_print-5Fview_&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=cZIjH_KYX5_apw_8MtAHQGgQO4hHZNsXHy3jb-f6A5bP6jiYYgAzmk2STFkeQsuG&s=nYsJAWKWyYZ8VFcYDuhaIDLn8gsHUK_b8-xYaWdAmjY&e=>
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
https://urldefense.proofpoint.com/v2/url?u=http-3A__docs.sparkfun.com&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=JsDsKeR7cZC8wbZhIlxxBQ&m=cZIjH_KYX5_apw_8MtAHQGgQO4hHZNsXHy3jb-f6A5bP6jiYYgAzmk2STFkeQsuG&s=FE_9ASYWpM7xDCiKsYJcUHHEdr08-AIwjQof6ytAUjo&e=
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This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
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Jim Lux
Mon, Apr 28, 2025 6:40 PM
A decided "maybe"
Yes, the differential corrections can be used to estimate the ionospheric component (and if differential position over short distance, things like solid earth tides) all of which are important when it comes to getting "better than a meter".
If you have a dual frequency receiver that alone helps you with the ionospheric corrections (because the delay is frequency dependent).
But as for the actual 1pps output from the receiver? That typically has other issues (e.g. it's synchronous with some internal clock, which may or may not be locked to the GPS time epoch).
On applications where time and position are important typically it's done with post processing. For instance, the SunRISE payloads in space will process the raw observables (L1 and L2) through a precision orbit determination process (GIPSYx) which produces a pos-goa file for position (and uncertainty) and a tdp (time dependent parameter) file which gives clock bias and rate (and uncertainties) for the receiver's clock.
Getting to sub-ns and sub-meter is certainly possible.
On Sun, 27 Apr 2025 08:52:12 +0000, drew wollin via time-nuts time-nuts@lists.febo.com wrote:
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]
Geoscience Australia Portal
This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
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A decided "maybe"
Yes, the differential corrections can be used to estimate the ionospheric component (and if differential position over short distance, things like solid earth tides) all of which are important when it comes to getting "better than a meter".
If you have a dual frequency receiver *that* alone helps you with the ionospheric corrections (because the delay is frequency dependent).
But as for the actual 1pps output from the receiver? That typically has other issues (e.g. it's synchronous with some internal clock, which may or may not be locked to the GPS time epoch).
On applications where time and position are important typically it's done with post processing. For instance, the SunRISE payloads in space will process the raw observables (L1 and L2) through a precision orbit determination process (GIPSYx) which produces a pos-goa file for position (and uncertainty) and a tdp (time dependent parameter) file which gives clock bias and rate (and uncertainties) for the receiver's clock.
Getting to sub-ns and sub-meter is certainly possible.
On Sun, 27 Apr 2025 08:52:12 +0000, drew wollin via time-nuts <time-nuts@lists.febo.com> wrote:
Hi All
I have a long-term interest in GPS/GNSS for accurate position, frequency and time.
Conventional GNSS receivers are accurate to a few metres and about 10 nanoseconds.
The accuracy can be improved by using correction information via RTK over the internet. The receiver needs to be within about 20 km of an RTK base station. The RTK base stations are linked and available as government or private correction networks, some of which are free. See the link for the Australian RTK network.
The RTK corrections are based on local space weather and the ionosphere's effect on the received satellite signal.
It is relatively inexpensive and easy to use these networks to get cm accuracy positioning. U-blox and Quectel make RTK-capable receivers, which are available from SparkFun and AliExpress. The receiver boards from AliExpress cost around US$50.
The receivers can be used with software from the respective manufacturers
With centimetre position accuracy, presumably, time pulse accuracy also improves. Does anyone know if that is the case? I looked on the web without success
The Quectel LG290P has a 1 PPS output that could be connected to other timing equipment.
I have an SRS PRS10 GPSDO cesium clock with an early single-satellite GPS receiver. I was thinking of replacing it with a 1 PPS signal from an RTK-corrected LG290P.
The other question, of course, is how do I measure if the time is better?
Regards Drew VK4ZXI
https://portal.ga.gov.au/persona/pa
https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/
[https://docs.sparkfun.com/SparkFun_LG290P_Quadband_GNSS_RTK_Breakout/print_view/%22https://i.ytimg.com/vi/a-aU4-Yodzg/default.jpg%22]
Introduction - SparkFun LG290P Quadband GNSS RTK Breakout Hookup Guide
The SparkFun Quadband GNSS RTK Breakout - LG290P (Qwiic) features the Quectel LG290P GNSS module. The board's dimensions, pin layout, and connectors are exactly the same as our vary popular SparkFun GPS-RTK-SMA Breakout - ZED-F9P (Qwiic); and can be used as a drop-in replacement.The board also accommodates users with a diverse choice of interfaces including UART, SPI 1, and I 2 C 1.
docs.sparkfun.com
[https://nonprod.portal.ga.gov.au/cache/images/portal_ga.png]
Geoscience Australia Portal
This portal (Geoscience Australia Portal Core) provides full access to Geoscience Australia data and other publically available data sources as well as suite of analytical and multi-criteria assessment tools to maximise the value of the data. A series of personas have been created on the Geoscience Australia Portal Core technology to meet specific stakeholder and project requirements.
portal.ga.gov.au
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