[time-nuts] Trimble SMT 360

[Logan Cummings]

Hi Michael, Bob,

     I had been very curious about this myself - the new ICM SMT 360
modules at first glance seem like a great deal - < $50 and 10MHz TCXO
disciplining built right in.

     I came across this paper which compares the older (GPS-only) ICM SMT
to a LEA-6T - the Trimble fares poorly in their testing.  The graphs don't
show an issue quite like yours Michael, so I'd be curious about the line of
questioning Bob brings up, how many satellites are being used by the
receiver - say in GPS-only mode?

http://www.imeko.org/publications/tc10-2013/IMEKO-TC10-2013-028.pdf

    Does anyone else have comparative experience with the new SMT modules
from Trimble? RES or ICM?

Thanks,
-Logan

On Tue, Apr 19, 2016 at 4:01 AM, Bob Camp <kb8tq at n1k.org> wrote:

> Hi
>
> The two plots shown appear to be identical. If they are actually two
> different
> runs, the problem repeats very closely.
>
> If the GPS is not in position hold *and* the antenna is less than ideal -
> That’s
> the sort of thing you may see. Essentially it’s got two locations it
> “thinks” are
> correct. Another possibility is a position hold situation with a very low
> satellite count.
> As a single observed satellite goes in and out of multi path, the solution
> goes all over the place.
> Again, you need a challenged antenna for this to happen. Pretty much all
> of this
> would be apparent from the normal messages out of the part.
>
> Bob
>
>
>
> > On Apr 18, 2016, at 10:13 PM, Michael Wouters <michaeljwouters at gmail.com>
> wrote:
> >
> > Does anyone have  experience with the Trimble SMT 360 ?
> >
> > I bought some of these four or five months after they were released.
> During
> > testing, the 1 pps output evidenced a problem, as shown in the attached
> > plot (the 1 pps is being measured against a Cs  beam standard), which is
> > not sawtooth-corrected. While there are longish periods of nominal
> > operation, the receiver seems to hop between two solutions.  This
> behaviour
> > is well out of specification.
> >
> > When I contacted Trimble support, they said that the firmware in the
> > receivers was very early, and replaced the receivers. However, the
> problem
> > was still evident with the new firmware. Trimble did not respond to
> further
> > emails.
> >
> > I tried many things to isolate the problem, including restricting the
> > receiver to GPS-only but I was unable to make an improvement.
> >
> > I would like to know if anyone else is operating an SMT 360 and if they
> > have seen any similar behaviour.
> >
> > Cheers[image: Inline image 2]
> > Michael[image: Inline image 1]
> > <smt360.png><smt360.png>_______________________________________________
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