[time-nuts] Chinese GPSDOs

Matthias Welwarsky time-nuts at welwarsky.de
Fri Apr 17 15:51:47 UTC 2020


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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