[time-nuts] Thunderbolt Rollover Testing

[Mark Sims]

Plus Trimble's usage is rather misleading...  you can do true overdetermined 
clock in either a static or moving environment... it properly requires more 
sats to be tracked than necessary to determine the time.   Position hold mode 
(and Trimble's overdetermined clock mode) requires a fixed location and can 
work with only one tracked sat,.   



> I very much prefer the “position hold” term for what it is doing compared to 
> Trimble’s “overdetermined” description. Overdetermined suggests that it has 
> more information than it needs to come up with the time.
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Re: [time-nuts] Thunderbolt Rollover Testing

[Bob Camp]

Hi

> On Mar 6, 2017, at 1:38 AM, Mark Sims  wrote:
> 
> Does it have a saved/surveyed position?  With a saved position you can 
> reasonable time performance with 1 sat.   Without a saved position all bets 
> are off,  there is no way for the receiver to determine the 
> receiver/satellite clock difference.
> 
> Trimble reports that the device is in "over-determined clock" mode if that is 
> how it is configured.  Even if it is in "over-determined clock" mode the 
> receiver may not have enough data to do anything effective.   Trimble's 
> overdetermined clock mode is basically a "position hold" mode.

I very much prefer the “position hold” term for what it is doing compared to 
Trimble’s “overdetermined” description. Overdetermined suggests that it has 
more information than it needs to come up with the time.

Bob

> 
> 
> 
>> I just re-checked this with a Resolution-T, and it does go into OD mode with 
>> all but 1
> SV masked from cold restart using a real SV.
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Re: [time-nuts] Thunderbolt Rollover Testing

[Trevor N .]

On Mon, 6 Mar 2017 00:38:35 +, you wrote:

>Does it have a saved/surveyed position?  With a saved position you can 
>reasonable time performance with 1 sat.   Without a saved position all bets 
>are off,  there is no way for the receiver to determine the receiver/satellite 
>clock difference.
>
>Trimble reports that the device is in "over-determined clock" mode if that is 
>how it is configured.  Even if it is in "over-determined clock" mode the 
>receiver may not have enough data to do anything effective.   Trimble's 
>overdetermined clock mode is basically a "position hold" mode.
>   
It will stay in 2d/3d mode if there is no stored position. With a
stored position the Resolution-T does seem to be pretty stable with
only 1 SV. With the simulator it will switch to OD mode for about 2
seconds, then its status changes to "no SVs usable" and it stops using
the simulated SV. I still have many navigation message changes to test
out -- something may work.
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[time-nuts] Thunderbolt Rollover Testing

[Mark Sims]

Does it have a saved/surveyed position?  With a saved position you can 
reasonable time performance with 1 sat.   Without a saved position all bets are 
off,  there is no way for the receiver to determine the receiver/satellite 
clock difference.

Trimble reports that the device is in "over-determined clock" mode if that is 
how it is configured.  Even if it is in "over-determined clock" mode the 
receiver may not have enough data to do anything effective.   Trimble's 
overdetermined clock mode is basically a "position hold" mode.
   


>I just re-checked this with a Resolution-T, and it does go into OD mode with 
>all but 1
SV masked from cold restart using a real SV.
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Re: [time-nuts] Thunderbolt Rollover Testing

[Trevor N .]

On Sun, 5 Mar 2017 18:35:25 +0100, you wrote:

>One thing a 6100 will let you do is to calibrate the PPS out of your “gizmo” 
>to +/- 5 ns (one sigma). While it’s 
>not an impressive number by TimeNuts standards, it is one of the few ways to 
>get that job done. 

I want to eventually characterize the delay of some amplified
antennas. It's reported that delay varies significantly over
temperature even for geodetic-grade antennas.

>> multiple synchronized single channel units), as I haven't yet been
>> able to get the Trimble Resolution boards to go into overdetermined
>> mode with a single simulated SV.
>
>It would be a bit alarming if you *could* get it to show overdetermined with 
>only a single clock source :)

It's quite odd at face value, but the Thunderbolt will go into
"overdetermined" mode with only the 1simulated SV.  I just re-checked
this with a Resolution-T, and it does go into OD mode with all but 1
SV masked from cold restart using a real SV.
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Re: [time-nuts] Thunderbolt Rollover Testing

[Bob Camp]

Hi

> On Mar 5, 2017, at 6:31 AM, Trevor N.  wrote:
> 
> On Sat, 4 Mar 2017 20:39:45 -0800, you wrote:
> 
>> Matthias Jelen did a test on the Trimble Thunderbolt here:
>> 
>> https://www.febo.com/pipermail/time-nuts/2014-September/086664.html
>> https://www.febo.com/pipermail/time-nuts/2015-May/091805.html
>> https://www.febo.com/pipermail/time-nuts/2015-May/091825.html
>> 
> 
> 
> Thanks for the links, I didn't see the 2015 test.  Currently the older
> Spirent simulators are going for very resonable prices on the 'bay.
> The GSS4100 can be had for under $200 and 6100s frequently pop up for
> $150.

One thing a 6100 will let you do is to calibrate the PPS out of your “gizmo” to 
+/- 5 ns (one sigma). While it’s 
not an impressive number by TimeNuts standards, it is one of the few ways to 
get that job done. 

>  Anything newer is still very expensive, though. It may be
> necessary to use a multichannel simulator for newer receivers (or
> multiple synchronized single channel units), as I haven't yet been
> able to get the Trimble Resolution boards to go into overdetermined
> mode with a single simulated SV.

It would be a bit alarming if you *could* get it to show overdetermined with 
only a single clock source :)

Bob

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Re: [time-nuts] Thunderbolt Rollover Testing

[Trevor N .]

On Sat, 4 Mar 2017 20:39:45 -0800, you wrote:

>Matthias Jelen did a test on the Trimble Thunderbolt here:
>
>https://www.febo.com/pipermail/time-nuts/2014-September/086664.html
>https://www.febo.com/pipermail/time-nuts/2015-May/091805.html
>https://www.febo.com/pipermail/time-nuts/2015-May/091825.html
>


Thanks for the links, I didn't see the 2015 test.  Currently the older
Spirent simulators are going for very resonable prices on the 'bay.
The GSS4100 can be had for under $200 and 6100s frequently pop up for
$150.  Anything newer is still very expensive, though. It may be
necessary to use a multichannel simulator for newer receivers (or
multiple synchronized single channel units), as I haven't yet been
able to get the Trimble Resolution boards to go into overdetermined
mode with a single simulated SV.
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Re: [time-nuts] Thunderbolt Rollover Testing

[Tom Van Baak]

> I didn't see any reports of anyone (successfully) implementing a test for it.
...
> I obtained all of the receivers the driver currently supports, along with a 
> Spirent GSS6100 simulator.
...

Hi Trevor,

Matthias Jelen did a test on the Trimble Thunderbolt here:

https://www.febo.com/pipermail/time-nuts/2014-September/086664.html
https://www.febo.com/pipermail/time-nuts/2015-May/091805.html
https://www.febo.com/pipermail/time-nuts/2015-May/091825.html

So we're all quite confident that the TBolt 1PPS and 10 MHz will be 
glitch-free. Mark Sims fixed his LH program so even the date & time will be 
correct. Still, the more tests the better, and the more thorough the better. 
Thanks for posting your results. The rest of us are envious that you own or 
have access to a GPS/GNSS simulator.

/tvb

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