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

[Vlad]

Its definitely VC TCXO. For the tests, I disconnected GPS-FC "embedded" 
antenna and connect it to my GPS distribution amplifier. In this case I 
could have GPS signal indoor. Its not perfect. But should be enough for 
troubleshooting.

I soldered TTL Serail sniffer to GPS-FC and I got following:

(Rx)@@At 00
(Rx)@@At 00
(Rx)@@Aw 00
(Rx)@@Ea 
060107DF0024190008E0BA0000000000000000000000000000000000000000000001000009000000190000001B000000130000001600000014000000020000000500000008
(Rx)@@En 
0101000A010000010000000000000001010202000021092FAF080019800000001B00000000130000000D16FFFFFFFF1400000039020000006F0500000000
(Rx)@@Ea 
060107DF00241A0009BC930000000000000000000000000000000000000000000001000009000000190000001B000000130000001600000014000000020000000500000008

(Rx)@@En 
0101000A010000010000000000000001010202000020112FAF08001F8000000007000000000C0000FACD0FFFFFFFFF1800381998060022189B0400000000
(Rx)@@Ea 
060107DF001F2F0002C27800000000000000000000000000000000000000000000010001110000001F000000070000000C0825A20F00000018000020060000200400000008
(Rx)@@En 
0101000A0100000100000000000000010102020000FD112FAF08001F8000000007000000000C0001E5820FFFFFFFFF1800381998060022189B0400000000
(Rx)@@Ea 
060107DF001F300003AD2C00000000000000000000000000000000000000000000010001110000001F000000070000000C0826A20F00000018000020060000200400000008

Which, I think, looks like Motorola protocol. And that means the GPS 
module is responsive.


Regards,
Vlad

On 2015-05-31 16:47, Bob Camp 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.