Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Bob kb8tq]

Hi

The target application is NTP with the PPS probably coming in via a RS-232 
serial port. 
Anything that jitters less than 200 ns is probably going to look “same / same “.

Bob

> On Jan 26, 2018, at 6:48 PM, Bryan _  wrote:
> 
> Thanks, forgot I have a Jupiter-T (D-120?) in my parts box , on that note out 
> of the two Trimble vs Jupiter-T. I think the Jupiter has a jitter of around 
> 15ns, not sure what the Jupiter-T specs but I believe 10-20ns.
> 
> 
> -=Bryan=-
> 
> 
> 
> From: time-nuts  on behalf of Mark Sims 
> 
> Sent: January 26, 2018 3:00 PM
> To: time-nuts@febo.com
> Subject: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / 
> other?)
> 
> The Trimble ... it is a newer design..   The Oncore is getting rather long in 
> the tooth and some have GPS week rollover issues.  The Trimble has a higher 
> clock rate and less 1PPS jitter.
> 
> 
> 
>> Which would be the preference as timing receiver Motorola Oncore or a 
>> Trimble Resolution T ?
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Bryan _]

Thanks, forgot I have a Jupiter-T (D-120?) in my parts box , on that note out 
of the two Trimble vs Jupiter-T. I think the Jupiter has a jitter of around 
15ns, not sure what the Jupiter-T specs but I believe 10-20ns.


-=Bryan=-



From: time-nuts  on behalf of Mark Sims 

Sent: January 26, 2018 3:00 PM
To: time-nuts@febo.com
Subject: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / 
other?)

The Trimble ... it is a newer design..   The Oncore is getting rather long in 
the tooth and some have GPS week rollover issues.  The Trimble has a higher 
clock rate and less 1PPS jitter.



> Which would be the preference as timing receiver Motorola Oncore or a Trimble 
> Resolution T ?
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Bob kb8tq]

Hi

Which ever you can get for the least money. Anything much over $10 is probably 
“over budget”. 

Bob

> On Jan 26, 2018, at 3:57 PM, Bryan _ <bpl...@outlook.com> wrote:
> 
> Which would be the preference as timing receiver Motorola Oncore or a Trimble 
> Resolution T ?
> 
> 
> -=Bryan=-
> 
> 
> 
> From: time-nuts <time-nuts-boun...@febo.com> on behalf of Pete Stephenson 
> <p...@heypete.com>
> Sent: January 26, 2018 12:48 PM
> To: Paride Legovini; Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / 
> Ublox / other?)
> 
> On 1/22/2018 4:38 PM, Paride Legovini via time-nuts wrote:
>> Dear fellow nuts,
>> 
>> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
>> looking for a good and possibly affordable timing GPS receiver.
> 
> As others have pointed out, NTP over the internet isn't usually more
> accurate than several tens of microseconds, so you have a lot of
> flexibility in the receiver you choose.
> 
> If you need something that's simple to interface, has RS-232 polarity
> signals, and is generally plug-and-play, the Garmin GPS 18x LVC is a
> good choice. It's robust, compact, and easy to wire to whatever device
> you want: in my case, I use a USB-A male plug connected to a USB port on
> my time server to provide the required 5V power and have the serial and
> PPS lines connected to the server's hardware serial port.
> 
> It's not strictly a timing receiver with a position hold mode, but it
> does produce a PPS output +/- 1 microsecond, and can do "position
> averaging" so it doesn't drift around more than a few meters when
> stationary.
> 
> It can output data in either NMEA format or the Garmin binary format,
> which is well-documented and supported by GPSd. Garmin's made the
> receiver for many years and has generally worked out the kinks with a
> bunch of firmware updates over the years.
> 
> Another alternative is the rather older Motorola Oncore UT+ receivers
> one can get on eBay for about $15 USD. No longer supported by the
> manufacturer and with hardware of unknown age, it might not be the best
> choice for critical systems. Still, they're true timing receivers with
> sawtooth correction, are easy to power with 5V, output TTL serial (so a
> MAX(3)232 can easily convert the data to RS-232 polarity) and a PPS
> signal, and are well-supported by NTPd. The Oncore driver for NTPd is a
> bit chatty in terms of what it logs every second, but that's easy enough
> to deal with. They're cheap enough to get a few to play with.
> 
> Cheers!
> -Pete
> 
> --
> Pete Stephenson
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> 
> 
> 
> and follow the instructions there.
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Bryan _]

Which would be the preference as timing receiver Motorola Oncore or a Trimble 
Resolution T ?


-=Bryan=-



From: time-nuts <time-nuts-boun...@febo.com> on behalf of Pete Stephenson 
<p...@heypete.com>
Sent: January 26, 2018 12:48 PM
To: Paride Legovini; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox 
/ other?)

On 1/22/2018 4:38 PM, Paride Legovini via time-nuts wrote:
> Dear fellow nuts,
>
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.

As others have pointed out, NTP over the internet isn't usually more
accurate than several tens of microseconds, so you have a lot of
flexibility in the receiver you choose.

If you need something that's simple to interface, has RS-232 polarity
signals, and is generally plug-and-play, the Garmin GPS 18x LVC is a
good choice. It's robust, compact, and easy to wire to whatever device
you want: in my case, I use a USB-A male plug connected to a USB port on
my time server to provide the required 5V power and have the serial and
PPS lines connected to the server's hardware serial port.

It's not strictly a timing receiver with a position hold mode, but it
does produce a PPS output +/- 1 microsecond, and can do "position
averaging" so it doesn't drift around more than a few meters when
stationary.

It can output data in either NMEA format or the Garmin binary format,
which is well-documented and supported by GPSd. Garmin's made the
receiver for many years and has generally worked out the kinks with a
bunch of firmware updates over the years.

Another alternative is the rather older Motorola Oncore UT+ receivers
one can get on eBay for about $15 USD. No longer supported by the
manufacturer and with hardware of unknown age, it might not be the best
choice for critical systems. Still, they're true timing receivers with
sawtooth correction, are easy to power with 5V, output TTL serial (so a
MAX(3)232 can easily convert the data to RS-232 polarity) and a PPS
signal, and are well-supported by NTPd. The Oncore driver for NTPd is a
bit chatty in terms of what it logs every second, but that's easy enough
to deal with. They're cheap enough to get a few to play with.

Cheers!
-Pete

--
Pete Stephenson
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Pete Stephenson]

On 1/22/2018 4:38 PM, Paride Legovini via time-nuts wrote:
> Dear fellow nuts,
> 
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.

As others have pointed out, NTP over the internet isn't usually more
accurate than several tens of microseconds, so you have a lot of
flexibility in the receiver you choose.

If you need something that's simple to interface, has RS-232 polarity
signals, and is generally plug-and-play, the Garmin GPS 18x LVC is a
good choice. It's robust, compact, and easy to wire to whatever device
you want: in my case, I use a USB-A male plug connected to a USB port on
my time server to provide the required 5V power and have the serial and
PPS lines connected to the server's hardware serial port.

It's not strictly a timing receiver with a position hold mode, but it
does produce a PPS output +/- 1 microsecond, and can do "position
averaging" so it doesn't drift around more than a few meters when
stationary.

It can output data in either NMEA format or the Garmin binary format,
which is well-documented and supported by GPSd. Garmin's made the
receiver for many years and has generally worked out the kinks with a
bunch of firmware updates over the years.

Another alternative is the rather older Motorola Oncore UT+ receivers
one can get on eBay for about $15 USD. No longer supported by the
manufacturer and with hardware of unknown age, it might not be the best
choice for critical systems. Still, they're true timing receivers with
sawtooth correction, are easy to power with 5V, output TTL serial (so a
MAX(3)232 can easily convert the data to RS-232 polarity) and a PPS
signal, and are well-supported by NTPd. The Oncore driver for NTPd is a
bit chatty in terms of what it logs every second, but that's easy enough
to deal with. They're cheap enough to get a few to play with.

Cheers!
-Pete

-- 
Pete Stephenson
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox /other?)

[Attila Kinali]

On Tue, 23 Jan 2018 13:33:08 -0500
ewkehren via time-nuts  wrote:

> The cheapest is not a 5T there are many 6 and 7 for $ 10. T gives you 
> nothing unless you  have saw tooth correction

It also gives additional performance when your skyview is very bad.
If you see only a small portion of the sky and only have 1-2 satellites
most of the time, then the position hold mode is the difference between
>1µs jitter and <100ns jitter, as Said Jackson noted a few years ago.

Attila Kinali

-- 
The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox /other?)

[Bob kb8tq]

Hi

The T software does support locked position. If your antenna location is so bad 
that this is of any use …. move the antenna. I can get full coverage with a 
modern
uBlox from a chair in the family room. 

A bit more information: If you are in an “urban canyon” (or maybe a real 
canyon) 
then indeed you can have some issues. In a normal suburban or urban setting, 
you should be able to lock to > 4 sat’s pretty much 100% of the time. With the 
newer modules (the 8 series) able to use multiple systems at one time, that all 
becomes even more true. Any timing errors you *might* see hopping from system
to system are way below what would matter for stratum 1 NTP. 

As noted earlier, if this stuff matters to you, setting up three NTP servers on 
your
LAN is a really good idea. Run them all off of GPS and all off of independent 
antennas.
If each antenna has it’s own “view” then your odds get even better on being 
able 
to keep it all going fine. The GPS part of that is maybe $10 vs $30. The 
servers 
are whatever you are paying for good single board computers these days. When 
they
go on sale, that could easily be < $100 for three of them. 

Bob

> On Jan 23, 2018, at 2:22 PM, Hal Murray  wrote:
> 
> 
> time-nuts@febo.com said:
>> The cheapest is not a 5T there are many 6 and 7 for $ 10. T gives you
>> nothing unless you  have saw tooth correctionBerrt Kehren 
> 
> Does the T firmware also support known-position mode where it can operate on 
> only one satellite?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox /other?)

[Hal Murray]

time-nuts@febo.com said:
> The cheapest is not a 5T there are many 6 and 7 for $ 10. T gives you
> nothing unless you  have saw tooth correctionBerrt Kehren 

Does the T firmware also support known-position mode where it can operate on 
only one satellite?


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox /other?)

[ewkehren via time-nuts]

The cheapest is not a 5T there are many 6 and 7 for $ 10. T gives you nothing 
unless you  have saw tooth correctionBerrt Kehren


Sent from my Galaxy Tab® A
 Original message From: Paride Legovini via time-nuts 
<time-nuts@febo.com> Date: 1/23/18  12:24 PM  (GMT-05:00) To: 
time-nuts@febo.com Subject: Re: [time-nuts] Suggestion for a timing GPS 
receiver (Trimble /
  Ublox /other?) 
On 2018-01-23 08:11, David J Taylor via time-nuts wrote:
> Dear fellow nuts,
> 
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
> []
> Am I overlooking something or missing interesting options?
> 
> Cheers,
> 
> Paride IZ3SUS
> 
> 
> Paride,
> 
> As Mark notes, you don't need a timing precision GPS receiver for NTP
> 
> [...]
>
> Stephen mentioned the newer series-8 ublox modules.  These are indeed
> excellent (and can receiver Galileo too)

Thanks David and thanks to you all for the advice you gave me, I
carefully read all your replies and learned quite a few things.

At this point I think I'll start tinkering with the cheapest module I
can get (and it will probably be a LEA-5T). Once I'll have everything
set up, if I'll be still having fun, I'll consider buying a newer
module, probably from the Ublox M8 family. We will see.

73,
Paride
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox /other?)

[Paride Legovini via time-nuts]

On 2018-01-23 08:11, David J Taylor via time-nuts wrote:
> Dear fellow nuts,
> 
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
> []
> Am I overlooking something or missing interesting options?
> 
> Cheers,
> 
> Paride IZ3SUS
> 
> 
> Paride,
> 
> As Mark notes, you don't need a timing precision GPS receiver for NTP
> 
> [...]
>
> Stephen mentioned the newer series-8 ublox modules.  These are indeed
> excellent (and can receiver Galileo too)

Thanks David and thanks to you all for the advice you gave me, I
carefully read all your replies and learned quite a few things.

At this point I think I'll start tinkering with the cheapest module I
can get (and it will probably be a LEA-5T). Once I'll have everything
set up, if I'll be still having fun, I'll consider buying a newer
module, probably from the Ublox M8 family. We will see.

73,
Paride
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox /other?)

[David J Taylor via time-nuts]

Dear fellow nuts,

I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
looking for a good and possibly affordable timing GPS receiver.
[]
Am I overlooking something or missing interesting options?

Cheers,

Paride IZ3SUS


Paride,

As Mark notes, you don't need a timing precision GPS receiver for NTP, a 
standard position GPS receiver is quite good enough providing it has a PPS 
output.  If you're thinking Raspberry Pi, there are some ready-made modules 
such as:


 https://store.uputronics.com/index.php?route=product/product_id=81

Stephen mentioned the newer series-8 ublox modules.  These are indeed 
excellent (and can receiver Galileo too), but a number of vendors 
advertising series-8 modules (on both eBay and Amazon) are using remarked 
series 5 or 6 chips without the series-8 functions.  Use the ublox u-center 
program to check anything you buy.  From Amazon, at least, I got an 
immediate refund.


73,
David GM8ARV
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 


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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Achim Gratz]

Paride Legovini via time-nuts writes:
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.

Unless you plan to use the timing receiver for some other function, it
really is overkill for the purpose of setting up an NTP server and
otherwise also requires you to set up a proper antenna in order to
benefit from the extra precision.

> Am I overlooking something or missing interesting options?

I think that setting up at least three "good enough" NTP stratum-1
servers in your network gets you much better synchronization than trying
to get a single one more precise.  To that end, you can set one up for
around $60 if you use a raspberryPi and a NavSpark mini w/ patch antenna
(if you have reasonable reception with that).  You'll find that the NTP
clients will not see any measurable improvement once you have the NTP
servers down below 10µs deviation and it's possible to get each
individual server consistently below 1µs with a bit of care.  Having at
least three stratum-1 in your network will keep the clients synchronized
correctly when inevitably one of the servers will have the occasional
problem that makes its time wander off for a while.


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Factory and User Sound Singles for Waldorf Q+, Q and microQ:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Gary E. Miller]

Yo Paride!

On Mon, 22 Jan 2018 16:38:01 +0100
Paride Legovini via time-nuts  wrote:

> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.

Before you bother looking at any GPS, you need to look at your server.

Hardly any Intel CPU can give you time resolution much better than
200 nS on a PPS in.  Raspberry Pi's actually have slightly better
clock resolution than Intel parts, just under 190 nS.

That resolution os worse than what you get out of any good modern
GPS.

By 'local resolution' I mean the shortest time interval you can
read by repeatedly doing clock_systime() calls.  clock_system() is
is many key ntpd paths.

The accuracy of your NTP server will be strongly affected by your server
choice, and the cheap RasPi is often one of the best for the job.  Fot
$70 you can get a RasPi and a u-blox-8 hat.  Add a few bits here and
there and you have a nifty stratum 1.  You'll find its harder than it
looks to make a better NTP than that combo.

Then, once you have a strong baseline, you can see what tricks you
can do to improve on that.

RGDS
GARY
---
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com  Tel:+1 541 382 8588

Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin


pgp_0UNQPV09D.pgp
Description: OpenPGP digital signature
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Attila Kinali]

On Mon, 22 Jan 2018 16:38:01 +0100
Paride Legovini via time-nuts  wrote:

> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
> 
> As far as I can tell there are a few common options. One is the Trimble
> Resolution T (or SMT), that should be good and proven. The major
> annoyance is converting the 3.3V TTL serial logic-level to RS232, but
> should be doable with a MAX3232 and a few capacitors.
> 
> Another option is this UBLOX LEA-5T:
> 
> https://www.ebay.it/itm/291769145465
> 
> The seller advertises an RS232 output pin, but I'm not sure it's
> actually available, and I'd need at least lines, one for the NMEA
> strings and one for the 1PPS signal. So, even if a RS232 TX pin is
> actually there, it is probably not enough to build a good reference
> clock, and I'd still need to convert some TTL levels to RS232...
> 
> Does anybody have experience with this receiver?
> How does it compare to the Resolution T/SMT?

For raw GPS PPS output, your performance is limited by multi-path
and how much of the sky you see. If you have perfect conditions,
I expect both to perform at the same level. Under not so perfect
conditions, go for the LEA. I have here a Trimble UCCM and 
Oscilloquartz Star4 GPSDO (using a LEA-5T). Compared to the Star4,
the UCCM is basically deaf. And mind you, the LEA-5 family came out
somewhen around 2006, ie is already a more than 10 year old design
and probably of the same age as the UCCM. The modern LEA's got a few
dB better yet.

For an NTP server, where you wont need anything better than 1µs
resolution, I think one of the many 10-bucks ublox LEA/NEO boards
that you can find on ebay are good enough (standard navigation
receivers give you better than 100ns accuracy). If you still want
to have a timing receiver, then go for one of the NEO-M8T, LEA-M8T or
LEA-6T based boards. Be aware that the NEO modules do not have the
circuit to provide power to the antenna, so it must be either
passive or you need an external bias-T. The LEA's can provide up
to 50mA (so no Zephyr!). 

If you want to step up your game and get even better stability,
take one of the LEA based GPSDOs (like the Star4 mentioned above).


Attila Kinali


-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Bob kb8tq]

Hi

It is doubtful that the pc board has an RS-232 to TTL converter onboard. The 
module it’s self
“talks” TTL levels rather than RS-232 levels. RS-232 to TTL adapters are dirt 
cheap and easy
to find on eBay. Make sure you get one that has control lines along with the 
basic RX and TX
functions. (You need to buffer the PPS signal). They also allow you to put in a 
“pulse stretcher”
on the PPS if the default is to short for your computer.

There is no value in a “timing” GPS vs a “normal” GPS for NTP. As long as you 
have a PPS output,
you are good to go. As noted elsewhere, something like the more modern M8 
series is just
as cheap and will do a better job. Simply get any of the modules and an 
adapter. Hook them up
and move on. Total cost should come in < $30 delivered. 

There are tons and tons of details on how do do all this in the archives. 

Bob

> On Jan 22, 2018, at 10:38 AM, Paride Legovini via time-nuts 
>  wrote:
> 
> Dear fellow nuts,
> 
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
> 
> As far as I can tell there are a few common options. One is the Trimble
> Resolution T (or SMT), that should be good and proven. The major
> annoyance is converting the 3.3V TTL serial logic-level to RS232, but
> should be doable with a MAX3232 and a few capacitors.
> 
> Another option is this UBLOX LEA-5T:
> 
> https://www.ebay.it/itm/291769145465
> 
> The seller advertises an RS232 output pin, but I'm not sure it's
> actually available, and I'd need at least lines, one for the NMEA
> strings and one for the 1PPS signal. So, even if a RS232 TX pin is
> actually there, it is probably not enough to build a good reference
> clock, and I'd still need to convert some TTL levels to RS232...
> 
> Does anybody have experience with this receiver?
> How does it compare to the Resolution T/SMT?
> 
> Another option is the Trimble Thunderbolt. This seems to do exactly what
> I need, but it costs at least ten times more than the other modules.
> Beside coming with a ready to use RS232 port and a nice case, does it
> have other advantages?
> 
> Am I overlooking something or missing interesting options?
> 
> Cheers,
> 
> Paride IZ3SUS
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> and follow the instructions there.

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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[Stephen Tompsett]

Why not consider a more recent current UBlox module?

e.g. the M8T  https://www.u-blox.com/en/product/neolea-m8t-series

A quick internet search will find several suppliers of ready made
boards/modules...


On 22/01/2018 15:38, Paride Legovini via time-nuts wrote:
> Dear fellow nuts,
>
> I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
> looking for a good and possibly affordable timing GPS receiver.
>
> As far as I can tell there are a few common options. One is the Trimble
> Resolution T (or SMT), that should be good and proven. The major
> annoyance is converting the 3.3V TTL serial logic-level to RS232, but
> should be doable with a MAX3232 and a few capacitors.
>
> Another option is this UBLOX LEA-5T:
>
> https://www.ebay.it/itm/291769145465
>
> The seller advertises an RS232 output pin, but I'm not sure it's
> actually available, and I'd need at least lines, one for the NMEA
> strings and one for the 1PPS signal. So, even if a RS232 TX pin is
> actually there, it is probably not enough to build a good reference
> clock, and I'd still need to convert some TTL levels to RS232...
>
> Does anybody have experience with this receiver?
> How does it compare to the Resolution T/SMT?
>
> Another option is the Trimble Thunderbolt. This seems to do exactly what
> I need, but it costs at least ten times more than the other modules.
> Beside coming with a ready to use RS232 port and a nice case, does it
> have other advantages?
>
> Am I overlooking something or missing interesting options?
>
> Cheers,
>
> Paride IZ3SUS
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>

-- 
Stephen Tompsett

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Re: [time-nuts] Suggestion for a timing GPS receiver (Trimble / Ublox / other?)

[ew via time-nuts]

Paride
The LEA-5T differs from other devices only that it has saw tooth information 
that can be used for correction or in a loop' I did a board and have one with 
variable delay using the 5T. Looking at the picture I do not even see an output 
for that information. Any later standard $10 module will be as good or better 
because he mentions 15 ns.
What do you need and please also look at what GPS is able to do without 
ionospheric correction
Bert
 
In a message dated 1/22/2018 11:07:52 AM Eastern Standard Time, 
time-nuts@febo.com writes:

 
 Dear fellow nuts,

I plan to build a decent GPS/GNSS-based Stratum 1 NTP server, and I'm
looking for a good and possibly affordable timing GPS receiver.

As far as I can tell there are a few common options. One is the Trimble
Resolution T (or SMT), that should be good and proven. The major
annoyance is converting the 3.3V TTL serial logic-level to RS232, but
should be doable with a MAX3232 and a few capacitors.

Another option is this UBLOX LEA-5T:

https://www.ebay.it/itm/291769145465

The seller advertises an RS232 output pin, but I'm not sure it's
actually available, and I'd need at least lines, one for the NMEA
strings and one for the 1PPS signal. So, even if a RS232 TX pin is
actually there, it is probably not enough to build a good reference
clock, and I'd still need to convert some TTL levels to RS232...

Does anybody have experience with this receiver?
How does it compare to the Resolution T/SMT?

Another option is the Trimble Thunderbolt. This seems to do exactly what
I need, but it costs at least ten times more than the other modules.
Beside coming with a ready to use RS232 port and a nice case, does it
have other advantages?

Am I overlooking something or missing interesting options?

Cheers,

Paride IZ3SUS
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