[time-nuts] DIY GPS-DO

[Magnus Danielson]

On 03/10/2012 03:05 PM, Azelio Boriani wrote:
> Sure it is message ID #21 to be looked for?

If I am to believe the FW manual I referred to, see page 83:

3.3.4 Navigation Data (ECEF Coordinates) ID# 21
Structure: Message ID#: 21
Rate (seconds): 1, 0.2 or 0.5 1

This log contains the receiver’s best available position and velocity in 
earth-centered-earth-fixed (ECEF) coordinates (see Figure 2 on Page 85). 
In addition, it reports height and velocity Figures of Merit (FOMs) and 
Dilution of Precision (DOP) values, which are quality indicators. For 
more information on the FOM and DOP, refer to the Glossary in the GPS+ 
Reference Manual available on our website at 
http://www.novatel.com/Downloads/docupdates.html.

1. SUPERSTAR II-based receivers are capable of a navigation rate of 1 
Hz. If you have a model with 5 Hz PVT, you can alternatively select 5 Hz 
(0.2) or 2 Hz (0.5). See a list of models on Page 133.

BYTE BIT DESCRIPTION UNITS TYPE OFFSET
1-4 Header, see Section 1.2.2, Message Block Structure starting on Page 13 0
5-12 GPS Time Range: 0.0 to 604800.0 s Double 4
13-14 Week weeks Short 12
15-22 X coordinate position m Double 14
23-30 Y coordinate position m Double 22
31-38 Z coordinate position m Double 30
39-42 Velocity vector along X-axis m/s Float 38
43-46 Velocity vector along Y-axis m/s Float 42
47-50 Velocity vector along Z-axis m/s Float 46
51-58 Clock bias s Double 50
59-66 Clock drift s/s Double 58
67-70 HFOM m Float 66
71-74 VFOM m Float 70
75-76 HDOP Resolution: 0.1 units N/A Ushort 74
77-78 VDOP Resolution: 0.1 units N/A Ushort 76

To get it, see page 26. You want to send

01 95 6A 00 00 01

If you treat the loop control properly, you should end up with something 
quite similar to the Thunderbolt.

Cheers,
Magnus

> On Sat, Mar 10, 2012 at 2:54 PM, Magnus Danielson<
> magnus at rubidium.dyndns.org>  wrote:
>
>> On 03/10/2012 02:38 PM, Filip Ozimek wrote:
>>
>>>
>>> It's an old novatel SUPERSTAR II.
>>>
>>
>> It's not hard to hook up a more stable 10 MHz oscillator to the Novatel
>> Superstar II. There is PCB foot-print for it and you need to move a
>> component (don't recall if it is a resistor or cap) to enable it.
>>
>> Get the message ID #21 and use the clock bias and clock drift measures to
>> steer the oscillator. It should be trivial to setup a FLL/PLL PI loop and
>> steer a DAC.
>>
>> http://webone.novatel.ca/assets/Documents/Manuals/om-20000086.pdf
>>
>> The PPS may still need some processing.
>>
>> I've intended to do this for ages, but never got off the ground.
>>
>> Cheers,
>> Magnus
>>
>>   Filip.
>>>
>>>
>>> Dnia 10 marca 2012 14:14 Bob Camp<lists at rtty.us>   napisał(a):
>>>
>>>   Hi
>>>>
>>>> Which module do you have?
>>>>
>>>> Bob
>>>>
>>>>
>>>>
>>>> On Mar 10, 2012, at 8:07 AM, Filip Ozimek<me_super at o2.pl>   wrote:
>>>>
>>>>   Hello,
>>>>>
>>>>>
>>>>> could you recommend me a good project of GPS-DO? I've got a GPS module
>>>>> with 1PPS output and a 20 MHz VCXO.
>>>>> As I understand to do a phaselock to 1 PPS signal one must build some
>>>>> kind of digital PLL. But I'm not sure
>>>>> how to calculate a correction signal to the VCXO and how to test such a
>>>>> disciplined oscillator.
>>>>>
>>>>> Filip.
>>>>>
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