[time-nuts] Re: help reviving Trimble UCCM-LPS GPSDO

[David G. McGaw]

I have a couple of Trimble UCCMs.  They would not come ready unless pin 
39 of the 50 pin ribbon connector is grounded.  This selects the 1PPS 
sync source.  Ground is internal, open is external.

73,

David N1HAC

On 12/24/21 7:39 AM, Wilko Bulte wrote:
> hi Francois,
>
> That EEVblog thread discusses (mainly) the UCCM produced by 
> Symmetricom.  If I remember correctly the Symm uses a 12V powered 
> OCXO, likely with another Vref output.  I sold my Symm, the two 
> Samsung UCCM I have found to be "just working always".
>
> In the meantime I have measured the EFC voltage of the Trimble over a 
> long period (interval 2 sec). Vref is 2.5V, taken from a LM336.
>
>
>
> In more detail
>
>
>
> At about 2.5V EFC voltage I measure 10MHz output, plus/minus a couple 
> of mHz. So using a Vref of 2.5V I do get an EFC voltage in the right 
> range.
>
> Unfortunately the Trimble never goes GPS locked. LH reports FFOM: Init 
> and Operation mode: Settling. Reported TFOM is 2.  No idea why it does 
> not lock, the GPS sees ample sats and is in position lock mode.
>
> Ideas welcome!
>
> Wilko
>
> > On 24 Dec 2021, at 12:41, F1CHF <F1CHF at free.fr> wrote:
> >
> > error in the Link ?
> > is it the good one ?
> > tks
> >
> >
> > https://www.eevblog 
> <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.eevblog%2F&data=04%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C5e368c4bed4442c4c81d08d9c702eb66%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637759637767230002%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=wItGRmNR%2F%2BipczR5Fu9sMZftMW6mTl4yXMBN22jBVC4%3D&reserved=0>
> > 
> com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/msg3
> > 78499/#msg3778499
> >
> > francois
> >
> >
> >
> > -------Message original-------
> >
> > De : Wilko Bulte
> > Date : 23/12/2021 20:50:36
> > A : Discussion of precise time and frequency measurement
> > Sujet : [time-nuts] Re: help reviving Trimble UCCM-LPS GPSDO
> >
> >
> >
> >>> On 23 Dec 2021, at 18:58, Attila Kinali <attila at kinali.ch> wrote:
> >>>
> >>> On Thu, 23 Dec 2021 12:14:48 -0500
> >>> Bob kb8tq <kb8tq at n1k.org> wrote:
> >>>
> >>> It’s a pretty good bet that the Vref is 5V
> >>
> >> A quick google lead me to this forum post:
> >> https://www.eevblog 
> <https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.eevblog%2F&data=04%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C5e368c4bed4442c4c81d08d9c702eb66%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637759637767239960%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=pDHdAlHCUGp%2FKIyE21WtGeBpei0yNt6mP0K3XqTWj04%3D&reserved=0>
> > 
> com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)/1325
> >
> >>
> >> Looks like the Vref is supposed to be 2.5V
> >
> > For the Symmetricom UCCM or for the Trimble?
> >
> > These UCCM are form-fit-function compatible but that does not mean the
> > circuits are the same. Or the OcXO.
> >
> > Samsung also produced UCCM, of which I have 2, both working fine. Again
> > different circuits, different GPS etc.
> >
> > Wilko
> >>
> >>Â Â Â Â Â Â Â Â Â Â  Attila Kinali
> >> --
> >> The driving force behind research is the question: "Why?"
> >> There are things we don't understand and things we always
> >> wonder about. And that's why we do research.
> >>Â Â Â Â Â Â  -- Kobayashi Makoto
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