[time-nuts] Trimble SMT 360

Bob Camp kb8tq at n1k.org
Tue Apr 19 07:01:25 EDT 2016


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]
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