Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Mike Millen]

On 22/12/2016 16:04, David wrote:

On Wed, 21 Dec 2016 19:29:00 +, you wrote:


You may be able to identify the initial steady current drawn by the TCXO
heater, then the cycling once it's hit the right temp?

If there's no change at all in average current as it warms then it may
not have a TCXO.

Mike

What heater?  The big advantage of a TCXO (temperature compensated)
over an OCXO (oven controlled) is the lack of a heater allows low
power operation.



My mistake... you're quite right.

Brain-fade, I'm afraid.

Mike

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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[David]

On Wed, 21 Dec 2016 19:29:00 +, you wrote:

> Can anyone comment on the following data, and whether they think the
> oscillator in "my" M8N is a XO or a TCXO ?
>
>Can you monitor the current draw from cold (ambient)?
>
>You may be able to identify the initial steady current drawn by the TCXO
>heater, then the cycling once it's hit the right temp?
>
>If there's no change at all in average current as it warms then it may
>not have a TCXO.
>
>Mike

What heater?  The big advantage of a TCXO (temperature compensated)
over an OCXO (oven controlled) is the lack of a heater allows low
power operation.
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Didier Juges]

TCXO usually refers to Temperature Compensated Crystal Oscillator (no heater), 
as opposed to Oven Controlled Crystal Oscillator (OCXO) which has an oven.
I would not expect a TCXO to become warm or draw more current at power up. An 
OCXO would.

Didier KO4BB

On December 21, 2016 1:29:00 PM CST, Mike Millen  
wrote:
>
> Can anyone comment on the following data, and whether they think
>the
>
> oscillator in "my" M8N is a XO or a TCXO ?
>
>
>Can you monitor the current draw from cold (ambient)?
>
>You may be able to identify the initial steady current drawn by the
>TCXO
>heater, then the cycling once it's hit the right temp?
>
>If there's no change at all in average current as it warms then it may
>not have a TCXO.
>
>Mike
>
>
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-- 
Sent from my Moto-X wireless tracker while I do other things.
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[EB4APL]

TCXO is not an OCXO, they don't have an oven. They compensate the 
temperature induced drift using a temperature sensor, a microcontroller  
and a table or parameter set for adjusting the output frequency. BTW, 
for some applications they are unsuitable as they adjust the frequency 
in steps.



Regards,

Ignacio EB4APL

El 21/12/2016 a las 20:29, Mike Millen escribió:


 Can anyone comment on the following data, and whether they think the


oscillator in "my" M8N is a XO or a TCXO ?



Can you monitor the current draw from cold (ambient)?

You may be able to identify the initial steady current drawn by the TCXO
heater, then the cycling once it's hit the right temp?

If there's no change at all in average current as it warms then it may
not have a TCXO.

Mike


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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Mike Millen]

 Can anyone comment on the following data, and whether they think the


oscillator in "my" M8N is a XO or a TCXO ?



Can you monitor the current draw from cold (ambient)?

You may be able to identify the initial steady current drawn by the TCXO
heater, then the cycling once it's hit the right temp?

If there's no change at all in average current as it warms then it may
not have a TCXO.

Mike


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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Kiwi Geoff]

Mike Cook wrote:
> It wouldn't surprise me, but  you have a reference for this?

I first read about this issue in the official Ublox forum Mike - try this link,

http://tinyurl.com/Fake-M8Ns

 - at time of writing it leads to some of the messages that discuss
the issue with photos and examples of M8N's that appear - not to be !

I must say, the two devices I have, appear to be genuine, and do
everything they should, and are a wonderful piece of kit.

My initial (now erroneous) thought was that maybe I could do a quick
overnight run with Lady Heather 5, to show up the M8N oscillator type.
Thanks to the excellent feedback on this thread, I now see why this is
not so, my overnight graph (seen in OP) is looking at a layer of
operation that somewhat hides the actual oscillator behaviour. I still
think it is an interesting graph, and shows the M8N can do a good job
of being a GNSS timing part.

Although as Mark S has said, it requires independent testing against a
reference to be done, rather than my graph - which essentially is the
M8N "self reporting" its quality.

>From my reading so far, the current best way to find out if you have a
genuine M8N is to use u-centre , and ask it to poll the UBX-MON-VER
command, which should return:

-
original firmware (2.01): SWVER 2.01 (75350) HWVER 0008 EXTENSION
2.01 (75331) PROTVER 15.00 FIS 0xEF4015 (79189) MOD NEO-M8N-0
GPS;SBAS;GLO;BDS;QZSS

after firmware update to (3.01): SWVER EXT CORE 3.01 (107900) HWVER
0008 EXTENSION ROM base 2.01 (75331) FWVER=SPG 3.01 PROTVER=18.00
FIS=0xEF4015 (100111) GPS;GLO;GAL;BDS;SBAS;IMES;QZSS
-

Take special note of the "FIS=" (Flash Information Structure) size.

Firmware Update to 3.01 can give you the (newly turned on) Galileo
system, however some people (like me) may choose to stay with Firmware
2.01 because it allows playing the RTK game thanks to the work of:

http://rtkexplorer.com/

Again, thank you for the replies to this thread, I have learned a lot,
and especially Bob Camp, who gave a nice explanation of the oscillator
in such a GNSS module.

Regards, Geoff (Christchurch, New Zealand).
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Bob Camp]

Hi

Given the short term stability limits on the frequency source (TCXO or XO) it’s 
a pretty
good bet that the crystal in both oscillators is very similar. There’s not a 
lot of difference
between a “normal” crystal and a “TCXO” crystal other than the angle of cut 
tolerance. 
Since the XO has frequency rate of change specs on it for the GPS to work, it’s 
got
some angle limits that get it pretty close to TCXO land even in that regard.

Bob


> On Dec 21, 2016, at 8:43 AM, Peter Reilley  wrote:
> 
> You seem to be assuming that the crystal in the TCXO is the same as the 
> crystal in the XO.
> Wouldn't it be likely that the crystal would be higher quality in the more 
> expensive
> product; the TCXO?   How would a cheap crystal vs an expensive crystal appear 
> different
> in the GPS data presented (ignoring the TC part)?
> 
> Pete.
> 
> 
> On 12/21/2016 7:37 AM, Bob Camp wrote:
>> Hi
>> 
>>> On Dec 21, 2016, at 4:20 AM, Mike Cook  wrote:
>>> 
>>> 
 Le 21 déc. 2016 à 00:08, Kiwi Geoff  a écrit :
 
 Hello All - and Seasons Greetings,
 
 One of the advantages of the recent hobby drone phenomena - it has
 brought to the market a lot of low cost GNSS modules that are
 lightweight for drone flight control systems. Those of us with other
 hobbies, like "Time Nuts" and RTK - these low cost modules can be a
 little goldmine for cost effective toys.
 
 However the dark side is that some vendors are re-badging lower cost
 modules, printing their own labels and marking as "Ublox M8N" for
 example.
>>> It wouldn't surprise me, but  you have a reference for this?
>>> 
 Can anyone comment on the following data, and whether they think the
 oscillator in "my" M8N is a XO or a TCXO ?
 
>>> I don’t thing that you can get find out from that data. Ublox indicate in 
>>> the product info sheets that the TCXO option is used to get to a first fix 
>>> quicker in weak signal conditions. It is not specified and I think that it 
>>> is logical, that there is an improved timing solution. I would expect that 
>>> both XO and TCXO versions are the same frequency and the better long term 
>>> stability of a TCXO not be an influence on the single shot quantization 
>>> error of the 1PPS.
>> 
>> The TCXO and XO both have similar short term stability at short tau. The only
>> advantage to the TCXO is faster time to first fix. If anything the XO will 
>> “spread”
>> the quantization error (sawtooth error) better than the TCXO. The TCXO has
>> more inflections in it’s frequency vs temperature curve. Thus there are more
>> opportunities for hanging bridges.
>> 
>> In both the TCXO and XO case, the PPS out of the module is based on the
>> clock edge closest to the PPS estimate. If the clock involved has a period of
>> 20 ns, the error will distribute over ~ +/- 10 ns. The process is identical 
>> regardless
>> of the oscillator. The distribution will be the same with both oscillators. 
>> As long as the
>> phase noise and short tau ADEV are in spec, the PPS estimate will be the same
>> in both cases.
>> 
>> Bob
>> 
>>> 
 _
 time-nuts mailing list -- time-nuts@febo.com
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 https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
 and follow the instructions there.
>>> "The power of accurate observation is commonly called cynicism by those who 
>>> have not got it. »
>>> George Bernard Shaw
>>> 
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Peter Reilley]

You seem to be assuming that the crystal in the TCXO is the same as the 
crystal in the XO.
Wouldn't it be likely that the crystal would be higher quality in the 
more expensive
product; the TCXO?   How would a cheap crystal vs an expensive crystal 
appear different

in the GPS data presented (ignoring the TC part)?

Pete.


On 12/21/2016 7:37 AM, Bob Camp wrote:

Hi


On Dec 21, 2016, at 4:20 AM, Mike Cook  wrote:



Le 21 déc. 2016 à 00:08, Kiwi Geoff  a écrit :

Hello All - and Seasons Greetings,

One of the advantages of the recent hobby drone phenomena - it has
brought to the market a lot of low cost GNSS modules that are
lightweight for drone flight control systems. Those of us with other
hobbies, like "Time Nuts" and RTK - these low cost modules can be a
little goldmine for cost effective toys.

However the dark side is that some vendors are re-badging lower cost
modules, printing their own labels and marking as "Ublox M8N" for
example.

It wouldn't surprise me, but  you have a reference for this?


Can anyone comment on the following data, and whether they think the
oscillator in "my" M8N is a XO or a TCXO ?


I don’t thing that you can get find out from that data. Ublox indicate in the 
product info sheets that the TCXO option is used to get to a first fix quicker 
in weak signal conditions. It is not specified and I think that it is logical, 
that there is an improved timing solution. I would expect that both XO and TCXO 
versions are the same frequency and the better long term stability of a TCXO 
not be an influence on the single shot quantization error of the 1PPS.


The TCXO and XO both have similar short term stability at short tau. The only
advantage to the TCXO is faster time to first fix. If anything the XO will 
“spread”
the quantization error (sawtooth error) better than the TCXO. The TCXO has
more inflections in it’s frequency vs temperature curve. Thus there are more
opportunities for hanging bridges.

In both the TCXO and XO case, the PPS out of the module is based on the
clock edge closest to the PPS estimate. If the clock involved has a period of
20 ns, the error will distribute over ~ +/- 10 ns. The process is identical 
regardless
of the oscillator. The distribution will be the same with both oscillators. As 
long as the
phase noise and short tau ADEV are in spec, the PPS estimate will be the same
in both cases.

Bob




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have not got it. »
George Bernard Shaw

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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Joseph Gray]

Some time ago, I bought two different modules from Reyax on ebay. One
module had a ublox M8N. Recently, I did some reading on several drone
forums about fake ublox modules from China. It seems that modules from
quite a few vendors are not genuine. From the information presented
about identifying the fakes, I am fairly confident that the modules I
bought from Reyax are genuine.

Joe Gray
W5JG
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Bob Camp]

Hi

> On Dec 21, 2016, at 4:20 AM, Mike Cook  wrote:
> 
> 
>> Le 21 déc. 2016 à 00:08, Kiwi Geoff  a écrit :
>> 
>> Hello All - and Seasons Greetings,
>> 
>> One of the advantages of the recent hobby drone phenomena - it has
>> brought to the market a lot of low cost GNSS modules that are
>> lightweight for drone flight control systems. Those of us with other
>> hobbies, like "Time Nuts" and RTK - these low cost modules can be a
>> little goldmine for cost effective toys.
>> 
>> However the dark side is that some vendors are re-badging lower cost
>> modules, printing their own labels and marking as "Ublox M8N" for
>> example.
> 
> It wouldn't surprise me, but  you have a reference for this? 
> 
>> Can anyone comment on the following data, and whether they think the
>> oscillator in "my" M8N is a XO or a TCXO ?
>> 
> 
> I don’t thing that you can get find out from that data. Ublox indicate in the 
> product info sheets that the TCXO option is used to get to a first fix 
> quicker in weak signal conditions. It is not specified and I think that it is 
> logical, that there is an improved timing solution. I would expect that both 
> XO and TCXO versions are the same frequency and the better long term 
> stability of a TCXO not be an influence on the single shot quantization error 
> of the 1PPS. 


The TCXO and XO both have similar short term stability at short tau. The only 
advantage to the TCXO is faster time to first fix. If anything the XO will 
“spread” 
the quantization error (sawtooth error) better than the TCXO. The TCXO has
more inflections in it’s frequency vs temperature curve. Thus there are more
opportunities for hanging bridges. 

In both the TCXO and XO case, the PPS out of the module is based on the 
clock edge closest to the PPS estimate. If the clock involved has a period of 
20 ns, the error will distribute over ~ +/- 10 ns. The process is identical 
regardless
of the oscillator. The distribution will be the same with both oscillators. As 
long as the
phase noise and short tau ADEV are in spec, the PPS estimate will be the same
in both cases. 

Bob

> 
> 
>> _
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> 
> "The power of accurate observation is commonly called cynicism by those who 
> have not got it. »
> George Bernard Shaw
> 
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Re: [time-nuts] Ublox M8N - have I a XO or TCXO ?

[Mike Cook]

> Le 21 déc. 2016 à 00:08, Kiwi Geoff  a écrit :
> 
> Hello All - and Seasons Greetings,
> 
> One of the advantages of the recent hobby drone phenomena - it has
> brought to the market a lot of low cost GNSS modules that are
> lightweight for drone flight control systems. Those of us with other
> hobbies, like "Time Nuts" and RTK - these low cost modules can be a
> little goldmine for cost effective toys.
> 
> However the dark side is that some vendors are re-badging lower cost
> modules, printing their own labels and marking as "Ublox M8N" for
> example.

It wouldn't surprise me, but  you have a reference for this? 

> Can anyone comment on the following data, and whether they think the
> oscillator in "my" M8N is a XO or a TCXO ?
> 

I don’t thing that you can get find out from that data. Ublox indicate in the 
product info sheets that the TCXO option is used to get to a first fix quicker 
in weak signal conditions. It is not specified and I think that it is logical, 
that there is an improved timing solution. I would expect that both XO and TCXO 
versions are the same frequency and the better long term stability of a TCXO 
not be an influence on the single shot quantization error of the 1PPS. 


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"The power of accurate observation is commonly called cynicism by those who 
have not got it. »
George Bernard Shaw

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