[ANSS-netops] Timing: IRIG-B conversion to NMEA

[Robert Wurth]

Mark

The problem you have is that you would have to create the GPS signal which
is not the nmea string, that is created by the GPS engine itself.
Rebroadcasting a GPS signal would be frowned upon by the FCC!!!

The other issue with a network based time system is you really never know
how long the packet takes to get thru the network, the delay could kill
you.  NTP uses the time stamp to approximate the delay and tries to
compensate for the delay.

If you can get a clean cat 5 from the outside to the instrument I would
just remove the GPS from the aldus/ k2 and convert the serial data and the
PPS signal to rs422 and send it down that way.  If they have central
network closets they may be able to patch you a dry cable.  Greg may be
able to help you with that.

As for fiber, if you are just running the nmea and pps signals Greg and I
built some boards to use with the 4td's to run the GPS over multimode
fiber.  I have also used B&B's fiber optic modem to send GPS signals over
fiber but either way the GPS would need to be removed from the unit unless
it has an external GPS interface.

Bob

On Wed, Mar 2, 2016 at 2:35 PM, Meremonte, Mark <mmeremonte at usbr.gov> wrote:

> Hi All,
>
> Have a K2-Altus where difficult to install GPS coax cable to a skyview
> location.   However, nearby is a network connection where IRIG-B is
> available over the Ethernet.  Anyone have knowledge of an IP device that
> could grab the IRIG-B signal, convert it to a standard RF GPS NMEA signal
> to input over coax to K2 in this instance?
>
> Or, I wonder if a logger that supported IP and NTP was installed, could
> that IRIG-B be converted into a NTP signal for logger to utilize?
>
> 3rd option I entertained is use of an Fiber Optic Network System which has
> a pair of devices which provides a standard RF GPS NMEA coax signal to
> device.  (very expensive system though).
>
> Regards,
> mark
>
> --
> *********************************************************
> Mark Meremonte         Geophysicist
> U.S. Bureau of Reclamation:  Seismology, Geomorphology, and Geophysics
> Group
> Denver Federal Center            Work: 303-445-3298  Cell: 303-808-3894
> POBox 25007, 85-833000      Email: mmeremonte at usbr.gov
> Denver, CO  80225                  Web: http://www.usbr.gov
> Ship:  U.S. Bureau of Reclamation, DFC, Bldg. 67-10th Floor, Denver, CO
> 80225
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-- 
Robert Wurth
AV Computer Tech
Department of Atmospheric and Earth Sciences
St Louis University
205 O'Neil Hall
3642 Lindell Blvd.
St. Louis, MO 63108, USA
Phone (314) 977-3137, 314-977-3135
 Fax (314) 977-3117
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