[time-nuts] Trimble SMT 360

[Bob Camp]

Hi

Actually there is one other possibility: 

If you have more than one “system” enabled *and* it’s doing “all in view” *and* it’s applying that 
to the timing *and* the population in view changes significantly … (whew !) 

As the solution pops between GPS and Glonass, you will get a time shift. Since it’s a “which one
is right?” sort of thing … Trimble probably does not want to get into the debate. They would love
to sell stuff to everybody.

Bob


> On Apr 19, 2016, at 3:32 PM, Logan Cummings <logan.cummings at gmail.com> wrote:
> 
> 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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