[time-nuts] Chinese GPSDOs

[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 <tpluess at ieee.org> 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 <steve-krull at cox.net> 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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