[time-nuts] Efratom/Datum GPSDO GPS-FC

Mike Cook michael.cook at sfr.fr
Mon Jun 1 13:02:55 EDT 2015


> Le 1 juin 2015 à 15:38, Vlad <time at patoka.org> a écrit :
> 
> 
> Paul,
> 
> For the testing purpose, I connecting GPS-FC to my GPS Distribution Amp. This is why antenna has disconnected on the picture. When I testing this unit - i connecting coax to it.
> Yesterday, I connected TTL serial to its Motorola Module, to see what is going on there. Here is screenshots:
> 
> http://www.patoka.ca/OCXO/Moto1.JPG
> http://www.patoka.ca/OCXO/Moto2.JPG
> 
> I left that unit up and running overnight, and even after that its still not show me real location and number of "visible" satelites is still "zero ».

Looks like it is Position Hold mode with a 0.0N 0.0E position. If you set this position the receiver will use it even though the receiver has been moved from the set position. The almanac will be no good, even though birds can be tracked. You probably need to reset so that it picks up a new almanac it and  let it do a survey. 
You might try WinOncore12 as a pilot. It’s free.

> 
> 
> Regards,
> Vlad
> 
> On 2015-05-31 21:50, paul swed wrote:
>> Quite difficult to see. But it appears the gps antenna cable is just
>> hanging there not connected to what I presume would be a antenna.
>> Regards
>> Paul
>> WB8TSL
>> On Sun, May 31, 2015 at 4:47 PM, Bob Camp <kb8tq at n1k.org> wrote:
>>> Hi
>>> If you look at the pictures you can see the oscillator they are using for
>>> the 10 MHz. At least as far as I can see
>>> it’s markings look like those of a VC TCXO. If you mount the device
>>> outdoors (as you must to get it to work) there
>>> will be a lot of temperature swings. In if the little oscillator *is* an
>>> OCXO, it’s not a fancy one. Between the
>>> simple oscillator and the outdoor location, you are unlikely to get very
>>> good performance out of the unit.
>>> The Oncore in this device has many of the same issues as ones we have
>>> discussed in other GPSDO’s. The
>>> design of the one in your gizmo is now approaching 20 years old. The
>>> interface strings are well documented
>>> and you should be able to tap into the module’s i/o stream to see what’s
>>> going on. I would recommend tacking
>>> a TTL to USB converter onto it and letting a terminal program show you
>>> what is happening.
>>> Bob
>>> > On May 31, 2015, at 11:58 AM, Vlad <time at patoka.org> wrote:
>>> >
>>> >
>>> >
>>> > Hello,
>>> >
>>> > Some time ago, I got Efratom/Datum GPS-FC item. The apparatus itself
>>> looks like good quality weather-proof aluminium case with embedded GPS
>>> antenna. It has only one connector. That connector is using to supply the
>>> power to the unit and as well to get 10Mhz signal from it.
>>> >
>>> > Here is the sticker inside of the devices:
>>> >
>>> > http://www.patoka.ca/OCXO/GPS-FC-LBL.JPG
>>> >
>>> > I tried to play with this device, however all my attempts to get 10 Mhz
>>> from it has failed.
>>> >
>>> > Here is how its looks inside:
>>> >
>>> > http://www.patoka.ca/OCXO/GPS-FC-PCB.JPG
>>> >
>>> >
>>> > AFAIK, there is Motorola Oncore GPS. I checked the 1PPS signal from that
>>> module and its looks good - I see the 1PPS on my scope.
>>> > Also I did check on TP4 on PCB. Looks like its an output from 10Mhz
>>> VTCXO. And I see the sine on the scope.
>>> >
>>> > I tried to contact Microesemi to obtain some service manual or even
>>> schematic for this unit, but unfortunately its not an option. Microsemi
>>> sent me only this manual:
>>> >
>>> > http://www.patoka.ca/OCXO/GPS-FC-Manual.pdf
>>> >
>>> >
>>> > Its appeared this units out of support for long period of time. So, I
>>> would ask if anybody knows anythings about it ? Especially I would be
>>> interested about what to measure/expect on control points on PCB. I still
>>> hope its repairable. Thanks in advance !
>>> >
>>> >
>>> >
>>> > --
>>> > WBW,
>>> >
>>> > V.P.
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> 
> -- 
> WBW,
> 
> V.P.
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