Re: [time-nuts] Segal law: freq difference for GPSDO

[Vlad]

Here is an update:

As I manually put the position for StarLoc II (Using Thunderbolt 
monitor), things has greatly improving and I am getting nice 10Mhz/1PPS 
signals from it. All the metrics on Thunderbolt monitor became "green".


I tried to leave StarLoc II for free run for a day. But even after that 
it didn't pickup the coordinates for some uncertain reason. I tried to 
replace Motorola Oncore GPS module by newer R5122U1154, but there was no 
difference( after one day it still shows 0,0 for its position). I did 
factory resets and restart Self-Survey. No luck. Only if I put the 
position manually its start to act properly. I am not sure if its a 
feature or its bad setup. As I mentioned before T-Bolt and StarLocII 
connected to the same Distribution Amplifier and use the same GPS 
Antenna. T-Bolt picking up position relatively fast. But StarLoc II 
somehow not doing it.


Now I am thinking, it could be not big deal to specify that position 
manually (copy/paste from T-Bolt). However, it will be nice to keep that 
information even if power was disconnected. Then next time the position 
will be available and not need to be specified. As I understood, UT 
Oncore modules has battery pin (and it is Pin1 on those 10-pin 
connectors). I am curious if it will works just to solder some basic 3V 
battery to it ? Thanks !


Regards,
Vlad




On 2016-03-30 13:38, Vlad wrote:

TB has three satellites in "green" state. I'll have a look to the
issue closely. Looks like "StarLoc II" little "deaf" in compare with
TB.
If its not locked - it could explain why OCXO is out of its 10Mhz. Its
just not disciplined.



On 2016-03-30 10:48, Chris Caudle wrote:

On Wed, March 30, 2016 12:04 am, Vlad wrote:

https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png


That unit is in holdover, it will not produce an accurate 10MHz 
output.

Only one satellite is in view, so either it does not have a good
connection to an antenna, or the receiver is broken.
How many usable satellites does the Thunderbolt show?


--
WBW,

V.P.
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Magnus Danielson]

On 03/30/2016 05:53 AM, Tom Van Baak wrote:

May be somebody could recognize, what 10.014 Mhz could be used for ?


It sort of looks more like an unlocked OCXO than a magic frequency.
Measure phase instead of frequency; see how the phase drifts over time.
Also check if the magic frequency varies or drifts over time.
See if the offset is constant in spite of a one hour power cycle of either 
GPSDO.


Its classical case of Segal's law: "A man with a watch knows what time
it is. A man with two watches is never sure". This is exact situation.
Now I am not sure which GPSDO (if any) is more accurate.


Yes, and www.leapsecond.com for where this madness ends up.


There is a old movie clip where a guy gets asked why he has three clocks 
on his wrist, and he replies:


One clock run slow,
One clock run fast
and one clock doesn't run at all.

Average that out, and you're pretty OK I guess :P

Cheers,
Magnus
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Bob Camp]

Hi

To contribute to the survey process, you need at least 4 satellites in the 
“locked on” state. More is better and 
4 may or may not get you into survey. If you are struggling to get enough 
stateless, it’s usually an antenna issue.

Bob

> On Mar 30, 2016, at 1:38 PM, Vlad  wrote:
> 
> 
> 
> TB has three satellites in "green" state. I'll have a look to the issue 
> closely. Looks like "StarLoc II" little "deaf" in compare with TB.
> If its not locked - it could explain why OCXO is out of its 10Mhz. Its just 
> not disciplined.
> 
> 
> 
> On 2016-03-30 10:48, Chris Caudle wrote:
>> On Wed, March 30, 2016 12:04 am, Vlad wrote:
>>> https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png
>> That unit is in holdover, it will not produce an accurate 10MHz output.
>> Only one satellite is in view, so either it does not have a good
>> connection to an antenna, or the receiver is broken.
>> How many usable satellites does the Thunderbolt show?
> 
> -- 
> WBW,
> 
> V.P.
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Vlad]

TB has three satellites in "green" state. I'll have a look to the issue 
closely. Looks like "StarLoc II" little "deaf" in compare with TB.
If its not locked - it could explain why OCXO is out of its 10Mhz. Its 
just not disciplined.




On 2016-03-30 10:48, Chris Caudle wrote:

On Wed, March 30, 2016 12:04 am, Vlad wrote:

https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png


That unit is in holdover, it will not produce an accurate 10MHz output.
Only one satellite is in view, so either it does not have a good
connection to an antenna, or the receiver is broken.
How many usable satellites does the Thunderbolt show?


--
WBW,

V.P.
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Chris Caudle]

On Wed, March 30, 2016 12:04 am, Vlad wrote:
> https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png

That unit is in holdover, it will not produce an accurate 10MHz output.
Only one satellite is in view, so either it does not have a good
connection to an antenna, or the receiver is broken.
How many usable satellites does the Thunderbolt show?

-- 
Chris Caudle


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Re: [time-nuts] Segal law: freq difference for GPSDO

[Henry Hallam]

On Tue, Mar 29, 2016 at 5:48 PM, Vlad  wrote:
>
> I tried to see the 1PPS on my oscilloscope. Here is the series of
> screenshots from that experiment:
>
> https://www.patoka.ca/OCXO/TBvsSL/

>From those scope shots it looks like one or both of the GPSDOs does
not have any kind of lock to GPS time.  The PPS leading edges from the
two receivers should be aligned to within a few tens to hundreds of
nanoseconds, but yours are hundreds of milliseconds apart.

The screenshot you have at
https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png shows a
receiver only tracking one satellite, which is not sufficient.  Maybe
the antenna signal connection to that unit is poor or maybe it's
defective. The filename says StarLoc but the window title says
Thunderbolt, which is it?

Good luck,
Henry
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Vlad]

May be somebody could recognize, what 10.014 Mhz could be used for 
?


It sort of looks more like an unlocked OCXO than a magic frequency.
Measure phase instead of frequency; see how the phase drifts over time.
Also check if the magic frequency varies or drifts over time.
See if the offset is constant in spite of a one hour power cycle of
either GPSDO.



To feed my curiosity, I disassembled Starloc II to have a look what is 
inside. There is Motorola GPS module and DATUM OCXO.
I measured 5V ref (stamped on PCB). Its looks good. The OCXO has 12V on 
its VSS pin. No visible damage there.
I put it back. I think its possible to replace DATUM OCXO by Morion. The 
pinout and voltage is the same. Moruib is slightly bigger in size, but 
should feet the case with minor modifications. However I postpone this 
exercise for now.


I don't have "native" software to manage StarLoc. But since its TSIP and 
I was using TB Monitor to see some information.


Here is how its looks like:

https://www.patoka.ca/OCXO/TBvsSL/StarLocIImonitor.png


Also there is series of screenshot from my Oscilloscope where I tried to 
compare 1PPS outputs



https://www.patoka.ca/OCXO/TBvsSL/



The TBolt/LH screen seems ok. Send some RS232 commands to the StarLoc.
Verify they are both receiving a good number of SV, and maybe even a
lot of the same set of SVN.


I am not sure if StarLoc is responsive for any commands. I need to dig 
it little more.



You can also remove the antenna on one or both units. See if the
unusual frequency offset and the ADEV curve looks the same with or
without antenna.


Thanks for the advise !


--
WBW,

V.P.
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Vlad]

I tried to see the 1PPS on my oscilloscope. Here is the series of 
screenshots from that experiment:


https://www.patoka.ca/OCXO/TBvsSL/

I also tried to catch something using HP5386A. However I was not able to 
measure the pulse.


Regards,
Vlad


On 2016-03-29 18:53, Henry Hallam wrote:

If you put the PPS outputs of the two GPSDOs into an oscilloscope and
trigger on the leading edge of one of them, what does the other look
like?

Henry

On Tue, Mar 29, 2016 at 12:56 PM, Vlad  wrote:



Hello,

I am looking for for the advise regarding some strange difference in
frequency between of two GPSDO: Trimble Thunderbolt and Datum Starloc 
II


Measuring by HP 5386A counter it shows something around 0.014 
delta.

If I connect TB as REF source then I am getting numbers like this:
10.01396 Mhz
If I connect StarLoc II as REF source then I am getting following:
9.98612 Mhz

May be somebody could recognize, what 10.014 Mhz could be used for 
?


TB Lady Heather screenshot
http://www.patoka.org/OCXO/TB-LH-Mar.png

Allan Deviation for several hours looks like this:
http://www.patoka.org/OCXO/TB-SL.png


I connected both GPSDO to Rigol DS1102E Oscilloscope to see the phase
difference. And its shows me the ellipse which change its orientation 
left

to right and vice versa.

Its classical case of Segal's law: "A man with a watch knows what time 
it
is. A man with two watches is never sure". This is exact situation. 
Now I am

not sure which GPSDO (if any) is more accurate.

I have no third GPSDO (or equivalent) to compare. TB and Starloc 
connected
to the same GPS Antenna distribution amplifier. So basically both 
using the
same antenna. Both of them was turned on at relatively the same time 
and

both was warmed up for few days.

I have a theory, that may be StarLoc II was customized somehow to 
produce

the freq. slightly different from 10Mhz. But its just a theory.
Is it worth to compare 1PPS outputs using something like AD8302 + DAC 
+ MCU

?

--
WBW,

V.P.
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--
WBW,

V.P.
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Tom Van Baak]

> May be somebody could recognize, what 10.014 Mhz could be used for ?

It sort of looks more like an unlocked OCXO than a magic frequency.
Measure phase instead of frequency; see how the phase drifts over time.
Also check if the magic frequency varies or drifts over time.
See if the offset is constant in spite of a one hour power cycle of either 
GPSDO.

> Its classical case of Segal's law: "A man with a watch knows what time 
> it is. A man with two watches is never sure". This is exact situation. 
> Now I am not sure which GPSDO (if any) is more accurate.

Yes, and www.leapsecond.com for where this madness ends up.

> I have a theory, that may be StarLoc II was customized somehow to 
> produce the freq. slightly different from 10Mhz. But its just a theory.
> Is it worth to compare 1PPS outputs using something like AD8302 + DAC + MCU ?

The TBolt/LH screen seems ok. Send some RS232 commands to the StarLoc. Verify 
they are both receiving a good number of SV, and maybe even a lot of the same 
set of SVN.

You can also remove the antenna on one or both units. See if the unusual 
frequency offset and the ADEV curve looks the same with or without antenna.

/tvb
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Re: [time-nuts] Segal law: freq difference for GPSDO

[Hal Murray]

> I have no third GPSDO (or equivalent) to compare.

There is the crystal in your 5386A.  Can you use that to measure the time 
between PPS pulses? (Some counters/timers don't go over a second and if the 
crystal is fast, the PPS will look slightly longer than a second.)

If both GPSDOs agree, you can calculate the actual frequency of the 5386A.

Then you can measure the 10 MHz signals and compute the actual frequency.


-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Segal law: freq difference for GPSDO

[Henry Hallam]

If you put the PPS outputs of the two GPSDOs into an oscilloscope and
trigger on the leading edge of one of them, what does the other look
like?

Henry

On Tue, Mar 29, 2016 at 12:56 PM, Vlad  wrote:
>
>
> Hello,
>
> I am looking for for the advise regarding some strange difference in
> frequency between of two GPSDO: Trimble Thunderbolt and Datum Starloc II
>
> Measuring by HP 5386A counter it shows something around 0.014 delta.
> If I connect TB as REF source then I am getting numbers like this:
> 10.01396 Mhz
> If I connect StarLoc II as REF source then I am getting following:
> 9.98612 Mhz
>
> May be somebody could recognize, what 10.014 Mhz could be used for ?
>
> TB Lady Heather screenshot
> http://www.patoka.org/OCXO/TB-LH-Mar.png
>
> Allan Deviation for several hours looks like this:
> http://www.patoka.org/OCXO/TB-SL.png
>
>
> I connected both GPSDO to Rigol DS1102E Oscilloscope to see the phase
> difference. And its shows me the ellipse which change its orientation left
> to right and vice versa.
>
> Its classical case of Segal's law: "A man with a watch knows what time it
> is. A man with two watches is never sure". This is exact situation. Now I am
> not sure which GPSDO (if any) is more accurate.
>
> I have no third GPSDO (or equivalent) to compare. TB and Starloc connected
> to the same GPS Antenna distribution amplifier. So basically both using the
> same antenna. Both of them was turned on at relatively the same time and
> both was warmed up for few days.
>
> I have a theory, that may be StarLoc II was customized somehow to produce
> the freq. slightly different from 10Mhz. But its just a theory.
> Is it worth to compare 1PPS outputs using something like AD8302 + DAC + MCU
> ?
>
> --
> WBW,
>
> V.P.
> ___
> time-nuts mailing list -- time-nuts@febo.com
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[time-nuts] Segal law: freq difference for GPSDO

[Vlad]

Hello,

I am looking for for the advise regarding some strange difference in 
frequency between of two GPSDO: Trimble Thunderbolt and Datum Starloc II


Measuring by HP 5386A counter it shows something around 0.014 delta.
If I connect TB as REF source then I am getting numbers like this: 
10.01396 Mhz
If I connect StarLoc II as REF source then I am getting following:  
9.98612 Mhz


May be somebody could recognize, what 10.014 Mhz could be used for ?

TB Lady Heather screenshot
http://www.patoka.org/OCXO/TB-LH-Mar.png

Allan Deviation for several hours looks like this:
http://www.patoka.org/OCXO/TB-SL.png


I connected both GPSDO to Rigol DS1102E Oscilloscope to see the phase 
difference. And its shows me the ellipse which change its orientation 
left to right and vice versa.


Its classical case of Segal's law: "A man with a watch knows what time 
it is. A man with two watches is never sure". This is exact situation. 
Now I am not sure which GPSDO (if any) is more accurate.


I have no third GPSDO (or equivalent) to compare. TB and Starloc 
connected to the same GPS Antenna distribution amplifier. So basically 
both using the same antenna. Both of them was turned on at relatively 
the same time and both was warmed up for few days.


I have a theory, that may be StarLoc II was customized somehow to 
produce the freq. slightly different from 10Mhz. But its just a theory.
Is it worth to compare 1PPS outputs using something like AD8302 + DAC + 
MCU ?


--
WBW,

V.P.
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