NMEA Jitter - NTP

This is a discussion on NMEA Jitter - NTP ; Hi all, Its time that I stop scratching my head with this issue :-D I have been working with ublox-Antaris Evalkit (borrowed from a friend). This GPS receiver spits NMEA sentences, UBX (ublox binary messages) and gives PPS. Very good...so ...

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Thread: NMEA Jitter

  1. NMEA Jitter

    Hi all,

    Its time that I stop scratching my head with this issue :-D

    I have been working with ublox-Antaris Evalkit (borrowed from a friend).
    This GPS receiver spits NMEA sentences, UBX (ublox binary messages)
    and gives PPS. Very good...so configured NTP with NMEA driver. At times
    it is observed that a shift of -1 second appears and continues for a day
    or more
    before it comes back to proper time.

    It is important that these GPS receivers generate NMEA sentences (at
    least one)
    in sync with the PPS which makes them usable.

    Comments and similar experiences ?

    Venu

  2. Re: NMEA Jitter


    >I have been working with ublox-Antaris Evalkit (borrowed from a friend).
    >This GPS receiver spits NMEA sentences, UBX (ublox binary messages)
    >and gives PPS. Very good...so configured NTP with NMEA driver. At times
    >it is observed that a shift of -1 second appears and continues for a day
    >or more
    >before it comes back to proper time.


    Sounds like a firmware bug.

    I've seen similar off by a second from NMEA units, but mine only last
    a few seconds. My units have a marginal view of the sky. They
    occasionally fade out. I've only seen the quirks when they are
    recovering from a fade out.

    If you get another one, you might let it run for a while (hour?)
    and then power cycle the unit so it has to get synchronized again
    and see if that fixes things.

    --
    These are my opinions, not necessarily my employer's. I hate spam.


  3. Re: NMEA Jitter

    Venu Gopal wrote:
    > Hi all,
    >
    > Its time that I stop scratching my head with this issue :-D
    >
    > I have been working with ublox-Antaris Evalkit (borrowed from a friend).
    > This GPS receiver spits NMEA sentences, UBX (ublox binary messages)
    > and gives PPS. Very good...so configured NTP with NMEA driver. At times
    > it is observed that a shift of -1 second appears and continues for a day
    > or more
    > before it comes back to proper time.


    Use the fudge command to move the NMEA error band so that it falls
    entirely within the correct PPS second. If the NMEA error band exceeds
    one second, get a better GPS receiver.
    >
    > It is important that these GPS receivers generate NMEA sentences (at
    > least one)
    > in sync with the PPS which makes them usable.
    >
    > Comments and similar experiences ?
    >
    > Venu


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