Re: [time-nuts] Chinese GPSDOs

2020-04-17 Thread ew via time-nuts
All three seam to be Chinese customer specific devices with focus on time. I 
bought three of the Trimble units we call them Tbolt 2 because of design 
similarities. On LH you will notice one thing like the original Tbolt it shows 
frequency jumps of 1 E -10 but also once every hour it does a major correction 
plus or minus. It is once an hour depending on when powered up. Frequency 
measurements confirm the excursions. The result is a maximum 1 pps excursion of 
 plus minus 4 nsec. This is comparable to the Furuno GT87 and four times better 
than Tbolt 1. All tests are 24 hours against a very good HP 5065A, backed up 
with Cs.
Bert Kehren
In a message dated 4/17/2020 11:52:31 AM Eastern Standard Time, 
time-n...@welwarsky.de writes:

On Freitag, 17. April 2020 16:04:15 CEST Steve - Home wrote:
> There are some Chinese GPSDOs currently on eBay, containing a Symmetricom
> 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any
> experience with them? It’s hard to tell from the pictures what the power
> requirements are. I know the GT-8031 is an older 8-channel receiver. I was
> considering one for a portable 10MHz reference. Anyone checked these out
> yet?

I own three of them. One of them is the Symmetricom/Furuno combination you 
mentioned. 
Another one has a Samsung OXCO and a Ublox LEA-6T receiver. A third one is 
supposedly a 
Trimble OXCO, but I have no idea which GPS receiver it is using. It's the only 
one in an 
enclosure and I didn't bother yet to open it.

They're all basically identical in form and structure. Same form factor, same 
inputs and 
outputs. I even bothered to make an adapter PCB with a switching regulator so 
that I can 
operate them more easily. They operate on 5.5V, taking in a little over 2A 
while the OCXO 
heats up.

I have no equipment yet to assess their performance. Anyway they're all scrap 
telecom 
equipment, many of them are unchecked and damaged, with components missing 
(ripped 
off of the PCBs), cables cut. The OCXOs are genuine as far as I can tell but 
they all have 
undocumented service life and you don't know what they have been exposed to 
mechanically.

If you plan to order one, I suggest to get one with an Ublox receiver. The 
Furuno is likely 
the oldest and weakest, it's also GPS-only. Afaict, the LEA-6T can at least 
receive GPS and 
GLONASS. From all three, I like the Samsung best, going by the performance I 
see when 
connecting it to "Lady Heather". The Symmetricom is the worst. Probably the 
OCXO has 
taken a hit.
The Trimble is so-so.

Of course there's a thread on the EEVblog forum dealing with all their variants:

https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/[1]
 

HTH.

BR,
Matthias
> 
> Steve
> WB0DBS
> 
> 
> 
> 
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[1] 
https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/
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Re: [time-nuts] Chinese GPSDOs

2020-04-17 Thread Matthias Welwarsky
On Freitag, 17. April 2020 16:04:15 CEST Steve - Home wrote:
> There are some Chinese GPSDOs currently on eBay, containing a Symmetricom
> 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any
> experience with them? It’s hard to tell from the pictures what the power
> requirements are. I know the GT-8031 is an older 8-channel receiver. I was
> considering one for a portable 10MHz reference. Anyone checked these out
> yet?

I own three of them. One of them is the Symmetricom/Furuno combination you 
mentioned. 
Another one has a Samsung OXCO and a Ublox LEA-6T receiver. A third one is 
supposedly a 
Trimble OXCO, but I have no idea which GPS receiver it is using. It's the only 
one in an 
enclosure and I didn't bother yet to open it.

They're all basically identical in form and structure. Same form factor, same 
inputs and 
outputs. I even bothered to make an adapter PCB with a switching regulator so 
that I can 
operate them more easily. They operate on 5.5V, taking in a little over 2A 
while the OCXO 
heats up.

I have no equipment yet to assess their performance. Anyway they're all scrap 
telecom 
equipment, many of them are unchecked and damaged, with components missing 
(ripped 
off of the PCBs), cables cut. The OCXOs are genuine as far as I can tell but 
they all have 
undocumented service life and you don't know what they have been exposed to 
mechanically.

If you plan to order one, I suggest to get one with an Ublox receiver. The 
Furuno is likely 
the oldest and weakest, it's also GPS-only. Afaict, the LEA-6T can at least 
receive GPS and 
GLONASS. From all three, I like the Samsung best, going by the performance I 
see when 
connecting it to "Lady Heather". The Symmetricom is the worst. Probably the 
OCXO has 
taken a hit.
The Trimble is so-so.

Of course there's a thread on the EEVblog forum dealing with all their variants:

https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/[1]
 

HTH.

BR,
Matthias
> 
> Steve
> WB0DBS
> 
> 
> 
> 
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[1] 
https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/
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Re: [time-nuts] Chinese GPSDOs

2020-04-17 Thread Bob kb8tq
Hi

GPSDO’s come from China for a very simple reason:

All the world’s scrap gear is sent to China for “reclamation”. It’s just 
another element in the great flow of material being recycled. For a 
variety of reasons China is the destination of choice for electronics 
scrap. 

Like it or not, telecom gear lives a pretty short life these days. It’s 
designed / sold / deployed and then 5 or 10 years later it’s replaced. 
When it’s pulled out, it likely goes in a container headed for China. 

The scrap out process on this stuff often is not pretty. If you head over
to Mr Google, there are is a lot of information on just how it gets done. 
This is very much *not* the way you would want it done in your back yard.

The net result is that we get sub assemblies out of this or that telecom
system dirt cheap. They mostly are < 15 years old, so reasonably 
state of the art. If it’s showing up in quantities you can notice on eBay, 
it was built for one of the big OEM’s. The assemblies were built by
somebody who very much does know what they are doing. 

Does this mean that a telecom GPSDO is the perfect answer to every
need? Of course not. Somewhere there was a spec for this or that 
module. They met that spec when new. The performance required
almost certainly focused on holdover. That is rarely a focus for a 
standard in a basement lab.

The Trimble Thunderbolt is simply one of the many GPSDO’s that 
fit into this category. There were lots of GPSDO’s (some quite good)
before the Tbolt. There have been many waves of parts since then. 
What is sure - when they are actively being reclaimed, the price will
be low and the quantities high. In a few years, prices will climb ….

Lots of fun 

Bob

> On Apr 17, 2020, at 10:52 AM, Tobias Pluess  wrote:
> 
> I wonder why the only (or at least, most of the) GPSDOs one can find on
> eBay are from China. Is there a reason for that?
> I would like to buy used GPSDOs and OCXOs from other sources because the
> stuff from China is often of doubtful pedigree and I would never 100% trust
> one of those. They often look like they were treated very badly and I have
> the impression that it is often unqualified personnel who pulls out the
> GPSDOs from whatever equipment they have there.
> The same is for Rb standards. I would already have one, but I can only find
> Chinese sources, so I better keep my money than I buy a Rb standard from
> which I don't know whether it was treated properly when removed from some
> electronic equipment.
> 
> Having said that I can add that I do have one of those dubious GPSDOs from
> there; however not the particular model you mentioned. The GPSDO works but
> I don't know whether it can be trusted. I once compared it to a Trimble
> Thunderbolt, but I am not sure whether it was the Trimble which was
> unstable or my own unit. It looks like the seller has made some
> modifications to it and I don't know why. Also, there is no measurement
> data available.
> 
> 
> Tobias
> HB9FSX
> 
> 
> On Fri, Apr 17, 2020 at 4:05 PM Steve - Home  wrote:
> 
>> There are some Chinese GPSDOs currently on eBay, containing a Symmetricom
>> 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any
>> experience with them? It’s hard to tell from the pictures what the power
>> requirements are. I know the GT-8031 is an older 8-channel receiver. I was
>> considering one for a portable 10MHz reference. Anyone checked these out
>> yet?
>> 
>> Steve
>> WB0DBS
>> 
>> 
>> 
>> 
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>> and follow the instructions there.
>> 
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Re: [time-nuts] Chinese GPSDOs

2020-04-17 Thread Paul Alfille
Leo Bodnar (Great Britain) makes some nice GPSDO devices for reasonable
prices, albeit TXCO.
http://www.leobodnar.com/shop/index.php?main_page=product_info=107_id=234

On Fri, Apr 17, 2020 at 10:53 AM Tobias Pluess  wrote:

> I wonder why the only (or at least, most of the) GPSDOs one can find on
> eBay are from China. Is there a reason for that?
> I would like to buy used GPSDOs and OCXOs from other sources because the
> stuff from China is often of doubtful pedigree and I would never 100% trust
> one of those. They often look like they were treated very badly and I have
> the impression that it is often unqualified personnel who pulls out the
> GPSDOs from whatever equipment they have there.
> The same is for Rb standards. I would already have one, but I can only find
> Chinese sources, so I better keep my money than I buy a Rb standard from
> which I don't know whether it was treated properly when removed from some
> electronic equipment.
>
> Having said that I can add that I do have one of those dubious GPSDOs from
> there; however not the particular model you mentioned. The GPSDO works but
> I don't know whether it can be trusted. I once compared it to a Trimble
> Thunderbolt, but I am not sure whether it was the Trimble which was
> unstable or my own unit. It looks like the seller has made some
> modifications to it and I don't know why. Also, there is no measurement
> data available.
>
>
> Tobias
> HB9FSX
>
>
> On Fri, Apr 17, 2020 at 4:05 PM Steve - Home  wrote:
>
> > There are some Chinese GPSDOs currently on eBay, containing a Symmetricom
> > 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any
> > experience with them? It’s hard to tell from the pictures what the power
> > requirements are. I know the GT-8031 is an older 8-channel receiver. I
> was
> > considering one for a portable 10MHz reference. Anyone checked these out
> > yet?
> >
> > Steve
> > WB0DBS
> >
> >
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
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Re: [time-nuts] Chinese GPSDOs

2020-04-17 Thread Tobias Pluess
I wonder why the only (or at least, most of the) GPSDOs one can find on
eBay are from China. Is there a reason for that?
I would like to buy used GPSDOs and OCXOs from other sources because the
stuff from China is often of doubtful pedigree and I would never 100% trust
one of those. They often look like they were treated very badly and I have
the impression that it is often unqualified personnel who pulls out the
GPSDOs from whatever equipment they have there.
The same is for Rb standards. I would already have one, but I can only find
Chinese sources, so I better keep my money than I buy a Rb standard from
which I don't know whether it was treated properly when removed from some
electronic equipment.

Having said that I can add that I do have one of those dubious GPSDOs from
there; however not the particular model you mentioned. The GPSDO works but
I don't know whether it can be trusted. I once compared it to a Trimble
Thunderbolt, but I am not sure whether it was the Trimble which was
unstable or my own unit. It looks like the seller has made some
modifications to it and I don't know why. Also, there is no measurement
data available.


Tobias
HB9FSX


On Fri, Apr 17, 2020 at 4:05 PM Steve - Home  wrote:

> There are some Chinese GPSDOs currently on eBay, containing a Symmetricom
> 10MHz oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any
> experience with them? It’s hard to tell from the pictures what the power
> requirements are. I know the GT-8031 is an older 8-channel receiver. I was
> considering one for a portable 10MHz reference. Anyone checked these out
> yet?
>
> Steve
> WB0DBS
>
>
>
>
> ___
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> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
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[time-nuts] Chinese GPSDOs

2020-04-17 Thread Steve - Home
There are some Chinese GPSDOs currently on eBay, containing a Symmetricom 10MHz 
oscillator and a Furuno GT-8031 GPS receiver. Has anyone had any experience 
with them? It’s hard to tell from the pictures what the power requirements are. 
I know the GT-8031 is an older 8-channel receiver. I was considering one for a 
portable 10MHz reference. Anyone checked these out yet?

Steve
WB0DBS




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