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Johnny B Good
Guest

Sat Jan 26, 2019 4:45 pm   



I've been rather mindful of the lack of off air frequency standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such services
somewhat problematical. Whilst I can receive the Radio 4 LW rubidium
based 198KHz standard ok, this is rather cursed with programme content
modulation making its use as a frequency reference a less than trivial
task.

Since there have been discussions by the official bodies involved over
their imminent demise as far as continuing such frequency and time
standards broadcast services, I'm a little reluctant to invest time and
energy into constructing a suitable reference source disciplined by such
services.

I had considered creating a source based on the R4 LW 198KHz rubidium
standard but its imminent ceasing as a calibration source, if not as a LW
broadcasting station altogether, has rather put me off such a project,
hence my interest in a GPSDO based solution as per the title of this
thread.

To that end, I've researched several DIY GPS based projects, eventually
homing in on the u-Blox series of GPS modules, notably the Neo-M8N for
its built in flash storage and TCXO and its programmability of the 1PPS
output to any frequency from .25Hz to 10MHz (and even a little beyond
though its 48MHz TCXO makes the obvious 10MHz choice a rather jittery one
compared to say 1, 2, 4 or 8MHz[1]).

Searching eBay for cost effective sources of these u-blox modules has
led me to the following no name brand item:

Ublox-NEO-M8N GPS navigation signal amplify module for arduino Rasppery PI

<https://www.ebay.co.uk/itm/Ublox-NEO-M8N-GPS-navigation-signal-amplify-
module-for-arduino-Rasppery-PI/312317200298?
hash=item48b78e47aa:g:iYcAAOSw1KRb6riz:rk:24:pf:0>

https://tinyurl.com/y7ypyhnn

The seller, though obviously yet another Chinese trader, does at least
hold this stock in the UK, making free delivery considerably quicker.

At 21 quid delivered[2], it seems a pretty good bargain but the lack of
detailed documentation on its use does rather beg the question in my mind
as to whether this lack is simply on account the item needs nothing
further than the data sheets from u-Blox and some basic programming
skills (Raspian, Arduino or even Z80 assembly!). Presumably, the
description, as sparse on details as it appears to my eye, must be more
than adequate when it comes to this seller's intended market of Arduino
and RasPi enthusiasts.

Basically, I'm asking whether this particular example is just what I
need as a starter to a more fully specced DIY GPSDO project or whether I
should be setting my sights a little higher?

As far as I can gather, I can simply use its 10MHz output directly
(after programming the 1PPS pin to output 10MHz) for use as (an albeit
jittery) 10MHz frequency calibration reference and look to combining it
with an VCXO (ovened or not) as and when I get the urge to improve it
into a respectable GPSDO calibration source. If I've got the wrong end of
the stick over such a 'Quick Fix' solution as I've envisaged, you're more
than welcome to correct my misunderstandings. :-)

[1] I'm thinking of using an NB3N502 14 MHz to 190 MHz (output) PLL Clock
Multiplier chip to recreate a less jittery 10MHz from a 1, 2 or possibly
even a 4MHz clock as a "Quick 'n' Dirty" 10MHz frequency reference
compromise between using the 10MHz direct and the full blown disciplined
10MHz VCTCXO/VCOCXO option.

[2] Annoyingly, both image options are the same single view of the item
so the Chinglish description of micro-usb and antenna option details
can't be verified too readily.

From the image, it looks to be sporting a ceramic plate antenna on its
underside and the only candidate for a 'micro-usb' connector alongside
the ext active antenna socket doesn't seem to be quite the right shape,
quite apart from its location seemingly, imo, being unusually close to an
antenna socket (GHz separation of operating frequencies not withstanding).

--
Johnny B Good

John Larkin
Guest

Sat Jan 26, 2019 6:45 pm   



On Sat, 26 Jan 2019 15:35:04 GMT, Johnny B Good
<johnny-b-good_at_invalid.ntlworld.com> wrote:

Quote:
I've been rather mindful of the lack of off air frequency standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such services
somewhat problematical. Whilst I can receive the Radio 4 LW rubidium
based 198KHz standard ok, this is rather cursed with programme content
modulation making its use as a frequency reference a less than trivial
task.

Since there have been discussions by the official bodies involved over
their imminent demise as far as continuing such frequency and time
standards broadcast services, I'm a little reluctant to invest time and
energy into constructing a suitable reference source disciplined by such
services.

I had considered creating a source based on the R4 LW 198KHz rubidium
standard but its imminent ceasing as a calibration source, if not as a LW
broadcasting station altogether, has rather put me off such a project,
hence my interest in a GPSDO based solution as per the title of this
thread.

To that end, I've researched several DIY GPS based projects, eventually
homing in on the u-Blox series of GPS modules, notably the Neo-M8N for
its built in flash storage and TCXO and its programmability of the 1PPS
output to any frequency from .25Hz to 10MHz (and even a little beyond
though its 48MHz TCXO makes the obvious 10MHz choice a rather jittery one
compared to say 1, 2, 4 or 8MHz[1]).

Searching eBay for cost effective sources of these u-blox modules has
led me to the following no name brand item:

Ublox-NEO-M8N GPS navigation signal amplify module for arduino Rasppery PI

https://www.ebay.co.uk/itm/Ublox-NEO-M8N-GPS-navigation-signal-amplify-
module-for-arduino-Rasppery-PI/312317200298?
hash=item48b78e47aa:g:iYcAAOSw1KRb6riz:rk:24:pf:0

https://tinyurl.com/y7ypyhnn

The seller, though obviously yet another Chinese trader, does at least
hold this stock in the UK, making free delivery considerably quicker.

At 21 quid delivered[2], it seems a pretty good bargain but the lack of
detailed documentation on its use does rather beg the question in my mind
as to whether this lack is simply on account the item needs nothing
further than the data sheets from u-Blox and some basic programming
skills (Raspian, Arduino or even Z80 assembly!). Presumably, the
description, as sparse on details as it appears to my eye, must be more
than adequate when it comes to this seller's intended market of Arduino
and RasPi enthusiasts.

Basically, I'm asking whether this particular example is just what I
need as a starter to a more fully specced DIY GPSDO project or whether I
should be setting my sights a little higher?

As far as I can gather, I can simply use its 10MHz output directly
(after programming the 1PPS pin to output 10MHz) for use as (an albeit
jittery) 10MHz frequency calibration reference and look to combining it
with an VCXO (ovened or not) as and when I get the urge to improve it
into a respectable GPSDO calibration source. If I've got the wrong end of
the stick over such a 'Quick Fix' solution as I've envisaged, you're more
than welcome to correct my misunderstandings. :-)

[1] I'm thinking of using an NB3N502 14 MHz to 190 MHz (output) PLL Clock
Multiplier chip to recreate a less jittery 10MHz from a 1, 2 or possibly
even a 4MHz clock as a "Quick 'n' Dirty" 10MHz frequency reference
compromise between using the 10MHz direct and the full blown disciplined
10MHz VCTCXO/VCOCXO option.

[2] Annoyingly, both image options are the same single view of the item
so the Chinglish description of micro-usb and antenna option details
can't be verified too readily.

From the image, it looks to be sporting a ceramic plate antenna on its
underside and the only candidate for a 'micro-usb' connector alongside
the ext active antenna socket doesn't seem to be quite the right shape,
quite apart from its location seemingly, imo, being unusually close to an
antenna socket (GHz separation of operating frequencies not withstanding).


What sort of frequency accuracy do you need?

A surplus rubidium will be awfully good. A typical trim range is +-1
PPB, so it will be pretty good as long as it locks.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics


Guest

Sat Jan 26, 2019 8:45 pm   



Johnny B Good wrote
Quote:
I've been rather mindful of the lack of off air frequency standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such services
somewhat problematical. Whilst I can receive the Radio 4 LW rubidium
based 198KHz standard ok, this is rather cursed with programme content
modulation making its use as a frequency reference a less than trivial
task.

Since there have been discussions by the official bodies involved over
their imminent demise as far as continuing such frequency and time
standards broadcast services, I'm a little reluctant to invest time and
energy into constructing a suitable reference source disciplined by such
services.

I had considered creating a source based on the R4 LW 198KHz rubidium
standard but its imminent ceasing as a calibration source, if not as a LW
broadcasting station altogether, has rather put me off such a project,
hence my interest in a GPSDO based solution as per the title of this
thread.

To that end, I've researched several DIY GPS based projects, eventually
homing in on the u-Blox series of GPS modules, notably the Neo-M8N for
its built in flash storage and TCXO and its programmability of the 1PPS
output to any frequency from .25Hz to 10MHz (and even a little beyond
though its 48MHz TCXO makes the obvious 10MHz choice a rather jittery one
compared to say 1, 2, 4 or 8MHz[1]).


If you search ebay for GPDSO you find many examples,
cheapest one I see on page one is a 51$ bid with free shipping:
https://www.ebay.com/itm/173752457978
try 55?

Johnny B Good
Guest

Sun Jan 27, 2019 6:45 am   



On Sat, 26 Jan 2019 09:31:21 -0800, John Larkin wrote:

Quote:
On Sat, 26 Jan 2019 15:35:04 GMT, Johnny B Good
johnny-b-good_at_invalid.ntlworld.com> wrote:

I've been rather mindful of the lack of off air frequency standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such services
somewhat problematical. Whilst I can receive the Radio 4 LW rubidium
based 198KHz standard ok, this is rather cursed with programme content
modulation making its use as a frequency reference a less than trivial
task.

Since there have been discussions by the official bodies involved over
their imminent demise as far as continuing such frequency and time
standards broadcast services, I'm a little reluctant to invest time and
energy into constructing a suitable reference source disciplined by such
services.

I had considered creating a source based on the R4 LW 198KHz rubidium
standard but its imminent ceasing as a calibration source, if not as a
LW broadcasting station altogether, has rather put me off such a
project, hence my interest in a GPSDO based solution as per the title of
this thread.

To that end, I've researched several DIY GPS based projects, eventually
homing in on the u-Blox series of GPS modules, notably the Neo-M8N for
its built in flash storage and TCXO and its programmability of the 1PPS
output to any frequency from .25Hz to 10MHz (and even a little beyond
though its 48MHz TCXO makes the obvious 10MHz choice a rather jittery
one compared to say 1, 2, 4 or 8MHz[1]).

Searching eBay for cost effective sources of these u-blox modules has
led me to the following no name brand item:

Ublox-NEO-M8N GPS navigation signal amplify module for arduino Rasppery
PI

https://www.ebay.co.uk/itm/Ublox-NEO-M8N-GPS-navigation-signal-amplify-
module-for-arduino-Rasppery-PI/312317200298?
hash=item48b78e47aa:g:iYcAAOSw1KRb6riz:rk:24:pf:0

https://tinyurl.com/y7ypyhnn

The seller, though obviously yet another Chinese trader, does at least
hold this stock in the UK, making free delivery considerably quicker.

At 21 quid delivered[2], it seems a pretty good bargain but the lack of
detailed documentation on its use does rather beg the question in my
mind as to whether this lack is simply on account the item needs nothing
further than the data sheets from u-Blox and some basic programming
skills (Raspian, Arduino or even Z80 assembly!). Presumably, the
description, as sparse on details as it appears to my eye, must be more
than adequate when it comes to this seller's intended market of Arduino
and RasPi enthusiasts.

Basically, I'm asking whether this particular example is just what I
need as a starter to a more fully specced DIY GPSDO project or whether I
should be setting my sights a little higher?

As far as I can gather, I can simply use its 10MHz output directly
(after programming the 1PPS pin to output 10MHz) for use as (an albeit
jittery) 10MHz frequency calibration reference and look to combining it
with an VCXO (ovened or not) as and when I get the urge to improve it
into a respectable GPSDO calibration source. If I've got the wrong end
of the stick over such a 'Quick Fix' solution as I've envisaged, you're
more than welcome to correct my misunderstandings. :-)

[1] I'm thinking of using an NB3N502 14 MHz to 190 MHz (output) PLL
Clock Multiplier chip to recreate a less jittery 10MHz from a 1, 2 or
possibly even a 4MHz clock as a "Quick 'n' Dirty" 10MHz frequency
reference compromise between using the 10MHz direct and the full blown
disciplined 10MHz VCTCXO/VCOCXO option.

[2] Annoyingly, both image options are the same single view of the item
so the Chinglish description of micro-usb and antenna option details
can't be verified too readily.

From the image, it looks to be sporting a ceramic plate antenna on its
underside and the only candidate for a 'micro-usb' connector alongside
the ext active antenna socket doesn't seem to be quite the right shape,
quite apart from its location seemingly, imo, being unusually close to
an antenna socket (GHz separation of operating frequencies not
withstanding).

What sort of frequency accuracy do you need?


Initially, the raw, jittery 10MHz straight out of the GPS module would
do me for starters, assuming I'm not underestimating the effect of the
jitter. I'm just trying to calibrate the 0.1ppm 50MHz TCXO I've installed
into an FY6600 DDS AWG as an upgrade to the 50ppm commodity 50MHz XO chip
it had originally been cursed with.

Quote:

A surplus rubidium will be awfully good. A typical trim range is +-1
PPB, so it will be pretty good as long as it locks.


As I understand it, the lamp life of rubidium oscillators is limited
(about 20 years I understand) so a surplus (presumably 2nd hand pull) is
a bit of a risky investment. The GPSDO option looks to be my best one so
far, especially if I can obtain almost instant gratification, assuming
the jitter doesn't represent an intractable problem to my calibrating
TCXOs against the 10MHz output of the GPS module.

If nothing else, the experience of building a GPSDO will be an education
in itself. It's one thing to read about the problems of short term jitter
on the GPS module's 1PPS output (regardless of the actual frequency
chosen) but you can't properly appreciate the dry statistics until you've
experienced the practical effects for yourself. I'm sure I'll obtain a
better understanding of the jitter problem soon enough once I have a GPS
module in my hands to play with. :-)


--
Johnny B Good

Gerhard Hoffmann
Guest

Sun Jan 27, 2019 8:45 am   



Am 26.01.19 um 16:35 schrieb Johnny B Good:
Quote:
I've been rather mindful of the lack of off air frequency standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such services


Is that you who has triggered the current thread on the time nuts mail list?


< http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >

regards,
Gerhard

Johnny B Good
Guest

Sun Jan 27, 2019 3:45 pm   



On Sun, 27 Jan 2019 07:58:59 +0100, Gerhard Hoffmann wrote:

Quote:
Am 26.01.19 um 16:35 schrieb Johnny B Good:
I've been rather mindful of the lack of off air frequency standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such
services

Is that you who has triggered the current thread on the time nuts mail
list?


http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com

Not guilty! Indeed, there's not a Cat in Hell's chance of my joining a
mailing list - I draw the line at signing up to fora. I think the EEVBlog
forum is only the second one I've ever signed up to over the past two
decades (and is the only one I'm currently active in (FSVo "active").

I've only posted my query here in the SED NG so far. It seemed a more
likely source for advice and guidance with regard to purchasing a
suitable GPS module. I may well land up posting this query as a new
thread in the EEVBlog forum to get a 'second opinion' (there doesn't seem
to be that much 'cross pollination' between SED and EEVBlog).

--
Johnny B Good

Phil Hobbs
Guest

Sun Jan 27, 2019 8:45 pm   



On 1/27/19 12:13 AM, Johnny B Good wrote:
Quote:
On Sat, 26 Jan 2019 09:31:21 -0800, John Larkin wrote:
sniiip


Quote:
What sort of frequency accuracy do you need?

Initially, the raw, jittery 10MHz straight out of the GPS module would
do me for starters, assuming I'm not underestimating the effect of the
jitter. I'm just trying to calibrate the 0.1ppm 50MHz TCXO I've installed
into an FY6600 DDS AWG as an upgrade to the 50ppm commodity 50MHz XO chip
it had originally been cursed with.


A surplus rubidium will be awfully good. A typical trim range is +-1
PPB, so it will be pretty good as long as it locks.

As I understand it, the lamp life of rubidium oscillators is limited
(about 20 years I understand) so a surplus (presumably 2nd hand pull) is
a bit of a risky investment. The GPSDO option looks to be my best one so
far, especially if I can obtain almost instant gratification, assuming
the jitter doesn't represent an intractable problem to my calibrating
TCXOs against the 10MHz output of the GPS module.


I haven't looked recently, but when I bought mine a used Rb was about
$100. At that price you could buy two, and swap out the first one if it
fails.

Quote:

If nothing else, the experience of building a GPSDO will be an education
in itself. It's one thing to read about the problems of short term jitter
on the GPS module's 1PPS output (regardless of the actual frequency
chosen) but you can't properly appreciate the dry statistics until you've
experienced the practical effects for yourself. I'm sure I'll obtain a
better understanding of the jitter problem soon enough once I have a GPS
module in my hands to play with. Smile


Yup. Beating it against a rubidium will be amusing as well.

Cheers

Phil Hobbs

(whose first job out of astronomy school was designing most of the
time/frequency electronics for the first civilian DBS system)


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

Gerhard Hoffmann
Guest

Sun Jan 27, 2019 9:45 pm   



Am 27.01.19 um 15:30 schrieb Johnny B Good:
Quote:
On Sun, 27 Jan 2019 07:58:59 +0100, Gerhard Hoffmann wrote:

Am 26.01.19 um 16:35 schrieb Johnny B Good:
I've been rather mindful of the lack of off air frequency standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such
services

Is that you who has triggered the current thread on the time nuts mail
list?


http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com

Not guilty! Indeed, there's not a Cat in Hell's chance of my joining a
mailing list - I draw the line at signing up to fora. I think the EEVBlog
forum is only the second one I've ever signed up to over the past two
decades (and is the only one I'm currently active in (FSVo "active").

I've only posted my query here in the SED NG so far. It seemed a more
likely source for advice and guidance with regard to purchasing a
suitable GPS module. I may well land up posting this query as a new
thread in the EEVBlog forum to get a 'second opinion' (there doesn't seem
to be that much 'cross pollination' between SED and EEVBlog).


The time-nuts list is very well-behaved and centered around the
technical content. There are no tracking cookies etc on a mail list
and you can use a throw-away address to subscribe if paranoid.
If you have Ghostery you can see how web sites track you.

Even social content is minimized, some recent stories about the early
days at HP are an exception to the rule. There are some olds farts
who spent their lives at HP; the list owner did the frequency
multipliers in the HP Cesium clocks, among other things IIRC.

You may look into the archives; this week someone asked exactly
your question.

In comparison, s.e.d. is a whorehouse.

Cheers,
Gerhard

Johnny B Good
Guest

Mon Jan 28, 2019 4:45 am   



On Sun, 27 Jan 2019 20:59:49 +0100, Gerhard Hoffmann wrote:

Quote:
Am 27.01.19 um 15:30 schrieb Johnny B Good:
On Sun, 27 Jan 2019 07:58:59 +0100, Gerhard Hoffmann wrote:

Am 26.01.19 um 16:35 schrieb Johnny B Good:
I've been rather mindful of the lack of off air frequency
standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such
services

Is that you who has triggered the current thread on the time nuts mail
list?


http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com


Not guilty! Indeed, there's not a Cat in Hell's chance of my joining
a
mailing list - I draw the line at signing up to fora. I think the
EEVBlog forum is only the second one I've ever signed up to over the
past two decades (and is the only one I'm currently active in (FSVo
"active").

I've only posted my query here in the SED NG so far. It seemed a more
likely source for advice and guidance with regard to purchasing a
suitable GPS module. I may well land up posting this query as a new
thread in the EEVBlog forum to get a 'second opinion' (there doesn't
seem to be that much 'cross pollination' between SED and EEVBlog).

The time-nuts list is very well-behaved and centered around the
technical content. There are no tracking cookies etc on a mail list and
you can use a throw-away address to subscribe if paranoid.
If you have Ghostery you can see how web sites track you.

Even social content is minimized, some recent stories about the early
days at HP are an exception to the rule. There are some olds farts who
spent their lives at HP; the list owner did the frequency multipliers in
the HP Cesium clocks, among other things IIRC.

You may look into the archives; this week someone asked exactly your
question.

In comparison, s.e.d. is a whorehouse.


Thanks for the advice, Gerhard.

I'll have another look at their archives and see if I can identify the
relevant thread (and work out whether it's ordered top down or bottom
up). A quick scan to find the start of the thread I was looking at left
me confused, possibly on account of the top posting nature of emails,
contrary to the common practice in usenet postings. Hopefully, I'll
figure it out and track down the relevant thread.

--
Johnny B Good

John Larkin
Guest

Mon Jan 28, 2019 4:45 am   



On Mon, 28 Jan 2019 02:55:05 GMT, Johnny B Good
<johnny-b-good_at_invalid.ntlworld.com> wrote:

Quote:
On Sun, 27 Jan 2019 20:59:49 +0100, Gerhard Hoffmann wrote:

Am 27.01.19 um 15:30 schrieb Johnny B Good:
On Sun, 27 Jan 2019 07:58:59 +0100, Gerhard Hoffmann wrote:

Am 26.01.19 um 16:35 schrieb Johnny B Good:
I've been rather mindful of the lack of off air frequency
standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such
services

Is that you who has triggered the current thread on the time nuts mail
list?


http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com


Not guilty! Indeed, there's not a Cat in Hell's chance of my joining
a
mailing list - I draw the line at signing up to fora. I think the
EEVBlog forum is only the second one I've ever signed up to over the
past two decades (and is the only one I'm currently active in (FSVo
"active").

I've only posted my query here in the SED NG so far. It seemed a more
likely source for advice and guidance with regard to purchasing a
suitable GPS module. I may well land up posting this query as a new
thread in the EEVBlog forum to get a 'second opinion' (there doesn't
seem to be that much 'cross pollination' between SED and EEVBlog).

The time-nuts list is very well-behaved and centered around the
technical content. There are no tracking cookies etc on a mail list and
you can use a throw-away address to subscribe if paranoid.
If you have Ghostery you can see how web sites track you.

Even social content is minimized, some recent stories about the early
days at HP are an exception to the rule. There are some olds farts who
spent their lives at HP; the list owner did the frequency multipliers in
the HP Cesium clocks, among other things IIRC.

You may look into the archives; this week someone asked exactly your
question.

In comparison, s.e.d. is a whorehouse.


Thanks for the advice, Gerhard.

I'll have another look at their archives and see if I can identify the
relevant thread (and work out whether it's ordered top down or bottom
up). A quick scan to find the start of the thread I was looking at left
me confused, possibly on account of the top posting nature of emails,
contrary to the common practice in usenet postings. Hopefully, I'll
figure it out and track down the relevant thread.


It is an interesting PLL, deriving a super stable 10 MHz clock from a
nasty wandering jitterey 1 PPS pulse.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Johnny B Good
Guest

Mon Jan 28, 2019 3:45 pm   



On Sun, 27 Jan 2019 19:03:53 -0800, John Larkin wrote:

Quote:
On Mon, 28 Jan 2019 02:55:05 GMT, Johnny B Good
johnny-b-good_at_invalid.ntlworld.com> wrote:

On Sun, 27 Jan 2019 20:59:49 +0100, Gerhard Hoffmann wrote:

Am 27.01.19 um 15:30 schrieb Johnny B Good:
On Sun, 27 Jan 2019 07:58:59 +0100, Gerhard Hoffmann wrote:

Am 26.01.19 um 16:35 schrieb Johnny B Good:
I've been rather mindful of the lack of off air frequency
standards
broadcast sources of late. Difficulties receiving the WWV shortwave
broadcasts and their Russian equivalents making the use of such
services

Is that you who has triggered the current thread on the time nuts
mail list?


http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com


Not guilty! Indeed, there's not a Cat in Hell's chance of my
joining a
mailing list - I draw the line at signing up to fora. I think the
EEVBlog forum is only the second one I've ever signed up to over the
past two decades (and is the only one I'm currently active in (FSVo
"active").

I've only posted my query here in the SED NG so far. It seemed a
more
likely source for advice and guidance with regard to purchasing a
suitable GPS module. I may well land up posting this query as a new
thread in the EEVBlog forum to get a 'second opinion' (there doesn't
seem to be that much 'cross pollination' between SED and EEVBlog).

The time-nuts list is very well-behaved and centered around the
technical content. There are no tracking cookies etc on a mail list
and you can use a throw-away address to subscribe if paranoid.
If you have Ghostery you can see how web sites track you.

Even social content is minimized, some recent stories about the early
days at HP are an exception to the rule. There are some olds farts who
spent their lives at HP; the list owner did the frequency multipliers
in the HP Cesium clocks, among other things IIRC.

You may look into the archives; this week someone asked exactly your
question.

In comparison, s.e.d. is a whorehouse.


Thanks for the advice, Gerhard.

I'll have another look at their archives and see if I can identify the
relevant thread (and work out whether it's ordered top down or bottom
up). A quick scan to find the start of the thread I was looking at left
me confused, possibly on account of the top posting nature of emails,
contrary to the common practice in usenet postings. Hopefully, I'll
figure it out and track down the relevant thread.

It is an interesting PLL, deriving a super stable 10 MHz clock from a
nasty wandering jitterey 1 PPS pulse.


That sounds very similar to the NB3N502 PLL multiplier chip I mentioned
in my op. I've still not been able to track down anything relevant to my
query in the archives though. Perhaps a bit of 'spoon feeding' maybe? :-)

Also, I've not had any answers with regard to the "Ublox-NEO-M8N GPS
navigation signal amplify module for arduino Rasppery PI" that I was
thinking of buying. On the face of it, it looks just the item I need (and
at the right sort of price).

The only reservations I have (possibly needless) are that it's a generic
no name unit with no further vendor supplied data other than that it's
meant to interface to Arduino, RasPi and PCs, has an external, powered,
antenna socket (and from the single image offered, includes a ceramic
plate antenna stuck to its underside) as well as a micro-usb socket.

I'm assuming (ASS-U-ME danger here) that the vendor doesn't really need
to offer any more information than he's given on the basis that the
target buyers will be more than familiar with hooking it up to their
Arduino/RasPi/PC based GPSDO project and the data sheets are freely
available from Ublox's web site to "Make programming a snap".

Since nobody seems to have bothered following the eBay link to cast an
expert eye over my GPS module prospect to offer an opinion on the wisdom
of such a purchase, I'm still none the wiser as to whether to place the
order or just hold out for something more suitable. It looks like I'll
have to post my query into the EEVBlog T&M forum in the hope of getting a
more concrete answer after all.

Usually, if you're after an opinion on something, a usenet posting is a
good starting point since usenet is, in general, an endless supply of
nothing but opinions, especially in the matter of purchasing
recommendations. Here, in SED, I find myself somewhat at a loss over the
seeming absence of expert opinion.

Never mind, life is so short and 21 quid so little an investment in
proving whether one's instincts for recognising a bargain can still be
trusted, I may as well place my order. At least I've not had any advice
to the contrary in my choice of GPS module.

--
Johnny B Good

Jeff Liebermann
Guest

Thu Jan 31, 2019 5:45 am   



On Sat, 26 Jan 2019 15:35:04 GMT, Johnny B Good
<johnny-b-good_at_invalid.ntlworld.com> wrote:

Quote:
To that end, I've researched several DIY GPS based projects, eventually
homing in on the u-Blox series of GPS modules, notably the Neo-M8N for
its built in flash storage and TCXO and its programmability of the 1PPS
output to any frequency from .25Hz to 10MHz ...


This GPSDO looks like it it has similar specs.
"GPS Variable Frequency Reference"
<http://clearskyinstitute.com/ham/gps/>
<http://clearskyinstitute.com/ham/gps/GPSReference-QEX-proof.pdf>
I'll probably be building something similar if my existing GPSDO again
goes into temporary insanity mode. One of the local hams built one
and claims excellent stability and performance, but I haven't seen it
yet.


--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Johnny B Good
Guest

Thu Jan 31, 2019 7:45 pm   



On Wed, 30 Jan 2019 19:55:09 -0800, Jeff Liebermann wrote:

Quote:
On Sat, 26 Jan 2019 15:35:04 GMT, Johnny B Good
johnny-b-good_at_invalid.ntlworld.com> wrote:

To that end, I've researched several DIY GPS based projects, eventually
homing in on the u-Blox series of GPS modules, notably the Neo-M8N for
its built in flash storage and TCXO and its programmability of the 1PPS
output to any frequency from .25Hz to 10MHz ...

This GPSDO looks like it it has similar specs.
"GPS Variable Frequency Reference"
http://clearskyinstitute.com/ham/gps/
http://clearskyinstitute.com/ham/gps/GPSReference-QEX-proof.pdf> I'll
probably be building something similar if my existing GPSDO again goes
into temporary insanity mode. One of the local hams built one and
claims excellent stability and performance, but I haven't seen it yet.


I checked out those clearskyinstitute links and what struck me just now
is how much time and money he could save if he were to build a MK II "GPS
Variable Frequency Reference" based on a Feeltech FY6600 or 6800 AWG to
deal with the DDS part of the project. :-)

Anyway, since I didn't receive any warnings against purchasing that Neo-
M8N based Arduino/RasPi adapter board, I went ahead and ordered one last
night (£21.00 with free postage) which I'm hoping to see arrive on the
5th or the 6th next week. Now I'm checking out Arduino nano pricing on
eBay.

However, afaiui, I should be able to program it via the usb port to give
me 10MHz on the PPS pin. I don't need the nano straight away and I'm
planning on buying some of those ultra low jitter NB3N502 PLL Clock
Multiplier chips so I can reprogram it to give me a 1 or 2MHz output
without the jitter you see from dividing a 48MHz TCXO clock signal down
to 10MHz.

All the fancy satellite numbers/quality statistics display and all such
frippery can wait for now. A minimal 10MHz GPS clock signal will be a
vast improvement over what I'm reduced to relying now.

Incidentally, my inspiration came from this chap's instructional youtube
videos here: <https://www.youtube.com/watch?v=lbns-FvpzK4>

--
Johnny B Good

Jeff Liebermann
Guest

Fri Feb 01, 2019 7:45 pm   



On Thu, 31 Jan 2019 17:56:35 GMT, Johnny B Good
<johnny-b-good_at_invalid.ntlworld.com> wrote:

Quote:
On Wed, 30 Jan 2019 19:55:09 -0800, Jeff Liebermann wrote:

On Sat, 26 Jan 2019 15:35:04 GMT, Johnny B Good
johnny-b-good_at_invalid.ntlworld.com> wrote:

To that end, I've researched several DIY GPS based projects, eventually
homing in on the u-Blox series of GPS modules, notably the Neo-M8N for
its built in flash storage and TCXO and its programmability of the 1PPS
output to any frequency from .25Hz to 10MHz ...

This GPSDO looks like it it has similar specs.
"GPS Variable Frequency Reference"
http://clearskyinstitute.com/ham/gps/
http://clearskyinstitute.com/ham/gps/GPSReference-QEX-proof.pdf> I'll
probably be building something similar if my existing GPSDO again goes
into temporary insanity mode. One of the local hams built one and
claims excellent stability and performance, but I haven't seen it yet.

I checked out those clearskyinstitute links and what struck me just now
is how much time and money he could save if he were to build a MK II "GPS
Variable Frequency Reference" based on a Feeltech FY6600 or 6800 AWG to
deal with the DDS part of the project. Smile


True. However, the article was intended for publication in QEX
magazine:
<http://www.arrl.org/qex>
which is the ham radio experimenters journal. Articles are not
intended to be fully documented construction articles and are often
work in progress. In other words, and exchange of ideas, not
products. A device does not need to be economical, optimal,
practical, and possibly even safe. Just some ideas which may or may
not fit well with your intended application. I kinda like the idea of
having a display with tiny worms (satellite tracks) crawling around
the screen.

If you want to save some time but not money, just buy something on
eBay and you're done:
<https://www.ebay.com/itm/Black-PLL-GPSDO-GPS-Tame-Disciplined-Clock-Sine-Wave-GPS-Receiver-10M-1PPS-US/163420544010>
Just $110 from Smog Angeles. If you don't mind burning time and
building something truly cheap, just build or buy a 10MHz OCXO, which
will probably be accurate and stable enough for most applications.

Quote:
Incidentally, my inspiration came from this chap's instructional youtube
videos here: <https://www.youtube.com/watch?v=lbns-FvpzK4


Thanks. Looks interesting. I'll view those videos tonite.

--
Jeff Liebermann jeffl_at_cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

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