PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna) - NTP

This is a discussion on PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna) - NTP ; So I have this fine receiver and have been a member of pool.ntp.org for several years. But I would like to take advantage of the PPS signal. The downside is that I have no idea where to start. The upside ...

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Thread: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)

  1. PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)

    So I have this fine receiver and have been a member of pool.ntp.org for
    several years. But I would like to take advantage of the PPS signal.
    The downside is that I have no idea where to start. The upside is that
    I can solder and read a simple schematic diagram. Any ideas?

    This is the first time in many years that I have used usenet. I am
    trying the google interface. My point is that I'm not totally
    confident that I will see any posts to this thread. So please feel
    free to send e-mail; I'm sure the spammers will.


  2. Re: PPS from TrueTime 468-DC GOES Time Receiver (withGPS antenna)

    simonpg wrote:
    > So I have this fine receiver and have been a member of pool.ntp.org for
    > several years. But I would like to take advantage of the PPS signal.
    > The downside is that I have no idea where to start. The upside is that
    > I can solder and read a simple schematic diagram. Any ideas?


    GOES was a time service received from a handful of weather satellites;
    while the antenna looks GPS-like, it's not a GPS. Unfortunately, the
    GOES time service was turned off a while (maybe 18 months?) ago. While
    there are sporadic reports of people receiving time from the satellites,
    there is no traceability and any results are totally untrustworthy.

    So, a neat box has turned into a paperweight...

    John
    _______________________________________________
    questions mailing list
    questions@lists.ntp.isc.org
    https://lists.ntp.isc.org/mailman/listinfo/questions


  3. Re: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)

    Thank you for responding. Please excuse me while I learn to work with
    this interface. My comments are interspersed below:

    Hal Murray wrote:
    > In article <1156450631.842127.105780@74g2000cwt.googlegroups.c om>,
    > "simonpg" writes:
    > >So I have this fine receiver and have been a member of pool.ntp.org for
    > >several years.

    > Have you found the web page for the driver?
    > http://www.cis.udel.edu/~mills/ntp/h...s/driver5.html
    > (That may not be the latest one, it's just what google found for me.)
    >


    I guess I didn't make myself clear enough. The clock works great:

    ntpq> peer
    remote refid st t when poll reach delay offset
    jitter
    ================================================== ============================
    *TRUETIME(0) .TRUE. 0 l 29 64 377 0.000 1.233
    1.901
    -clepsydra.dec.c .GPS. 1 u 504 1024 377 56.294 16.420
    0.023
    -clock.xmission. .GPS. 1 u 567 1024 377 81.726 15.580
    1.204
    +bigben.cac.wash .USNO. 1 u 553 1024 377 46.023 15.031
    2.000
    -time-nw.nist.go .ACTS. 1 u 566 1024 377 36.026 20.802
    0.702
    +clock.sjc.he.ne .CDMA. 1 u 509 1024 377 54.394 15.218
    0.100
    LOCAL(0) .LOCL. 10 l 35 64 377 0.000 0.000
    0.004

    > Lots of info here:
    > http://www.leapsecond.com/museum/468-dc/theory.htm
    > That doesn't mention a PPS signal. It says the signal is 468 MHz
    > so I wouldn't be surprised if a GPS antenna filtered that out.


    Yup, it does, "4-5 A phase locked receiver is used to receive and
    recover raw data from the satellite signal. The raw data is processed
    by analog circuitry and then passed to a microprocessor for conversion
    to useful outputs; among which are a visual display, one Hertz and one
    kilo Hertz timing pulses." It's just a little hidden.

    >
    > The usual approach with a PPS signal is to connect it to
    > one of the RS-232 modem control signals. (I forget which one, but
    > it should be easy to find.) Most of the PPS signals are TTL levels


    DCD (Data Carrier Detect)

    > rather than RS-232. If you want to get fancy you can wire up a
    > level converter (MAX-232) type chip but it will almost-for-sure
    > work with a direct connection. You do have to get the inversion
    > right though - MAX-232 type chips are inverters. Software can
    > normaly use either.
    >


    So, both the 1 and the 1K Hz pulses are available in the form of a BNC
    connector. I know that TTL stands for Transistor To Transistor Logic,
    but I don't know if that looks like a BNC connector.

    > Once you get the signal into your box, try the ATOM (aka PPS) driver.
    >
    > Is GEOS still working? I found this note from June 2005 saying it
    > was going off the air:
    > http://www.febo.com/pipermail/time-n...ne/001050.html
    >


    I guess GOES is indeed dead, but we have GPS now. Truetime came out
    with a replacement antenna that converted the GPS signal to something
    that makes the 486-DC happy, so I am happy.

    >
    > --
    > The suespammers.org mail server is located in California. So are all my
    > other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
    > commercial e-mail to my suespammers.org address or any of my other addresses.
    > These are my opinions, not necessarily my employer's. I hate spam.



  4. Re: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)

    Thank you for your response! My comments are interspersed below.

    John Ackermann N8UR wrote:
    > simonpg wrote:
    > > So I have this fine receiver and have been a member of pool.ntp.org for
    > > several years. But I would like to take advantage of the PPS signal.
    > > The downside is that I have no idea where to start. The upside is that
    > > I can solder and read a simple schematic diagram. Any ideas?

    >
    > GOES was a time service received from a handful of weather satellites;
    > while the antenna looks GPS-like, it's not a GPS. Unfortunately, the
    > GOES time service was turned off a while (maybe 18 months?) ago. While
    > there are sporadic reports of people receiving time from the satellites,
    > there is no traceability and any results are totally untrustworthy.
    >
    > So, a neat box has turned into a paperweight...
    >


    It would have had Truetime not come out with a replacement antenna that
    does a GPS to GOES conversion:

    ntpq> peer
    remote refid st t when poll reach delay offset
    jitter
    ================================================== ============================
    *TRUETIME(0) .TRUE. 0 l 50 64 377 0.000 2.831
    1.619
    -clepsydra.dec.c .GPS. 1 u 158 1024 377 56.722 17.000
    0.222
    +clock.xmission. .GPS. 1 u 220 1024 377 79.953 14.986
    0.955
    -bigben.cac.wash .USNO. 1 u 210 1024 377 42.859 15.810
    0.323
    -time-nw.nist.go .ACTS. 1 u 222 1024 377 36.091 21.114
    1.429
    +clock.sjc.he.ne .CDMA. 1 u 161 1024 377 53.454 15.612
    0.382
    LOCAL(0) .LOCL. 10 l 2 64 377 0.000 0.000
    0.004

    So it should still be a neat box.

    > John
    > _______________________________________________
    > questions mailing list
    > questions@lists.ntp.isc.org
    > https://lists.ntp.isc.org/mailman/listinfo/questions



  5. Re: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)


    >So, both the 1 and the 1K Hz pulses are available in the form of a BNC
    >connector. I know that TTL stands for Transistor To Transistor Logic,
    >but I don't know if that looks like a BNC connector.


    TTL is the electrical signal level. BNC is the mechanical connector.

    You need to build a cable that has a BNC connector on one end
    and a DB-9 on the other.

    You can add the PPS signal to the existing serial cable if you want
    or use a separate serial port.

    If your existing cable has a molded plug you can't easily add it.
    You can either chop the plug off and add a new one, or make an
    adapter cable with two plugs, one of each sex, merging the PPS
    in on one end.

    --
    The suespammers.org mail server is located in California. So are all my
    other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
    commercial e-mail to my suespammers.org address or any of my other addresses.
    These are my opinions, not necessarily my employer's. I hate spam.


  6. Re: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)

    Hacking up a serial cable is no problem. I'm just worried about frying
    something inside the 486-DC. Could I expect to see an LED lighting up
    on one of those RS-232 signal testers? How about a Volt/Ohm Meter? Or
    am I worring about nothing? So I'll hook the ring of the BNC to pin 1
    of the DB-9, and the tip to whatever DCD is? Do I need to worry about
    ground loops if I use the same serial port? (whine, whine, whine)
    It's just hard to get the 486-DC fixed; know what I mean?

    Hal Murray wrote:
    > >So, both the 1 and the 1K Hz pulses are available in the form of a BNC
    > >connector. I know that TTL stands for Transistor To Transistor Logic,
    > >but I don't know if that looks like a BNC connector.

    >
    > TTL is the electrical signal level. BNC is the mechanical connector.
    >
    > You need to build a cable that has a BNC connector on one end
    > and a DB-9 on the other.
    >
    > You can add the PPS signal to the existing serial cable if you want
    > or use a separate serial port.
    >
    > If your existing cable has a molded plug you can't easily add it.
    > You can either chop the plug off and add a new one, or make an
    > adapter cable with two plugs, one of each sex, merging the PPS
    > in on one end.
    >
    > --
    > The suespammers.org mail server is located in California. So are all my
    > other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
    > commercial e-mail to my suespammers.org address or any of my other addresses.
    > These are my opinions, not necessarily my employer's. I hate spam.



  7. Re: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)

    In article <1156547281.444666.212940@h48g2000cwc.googlegroups. com>,
    "simonpg" writes:
    >Hacking up a serial cable is no problem. I'm just worried about frying
    >something inside the 486-DC. Could I expect to see an LED lighting up
    >on one of those RS-232 signal testers? How about a Volt/Ohm Meter? Or
    >am I worring about nothing? So I'll hook the ring of the BNC to pin 1
    >of the DB-9, and the tip to whatever DCD is? Do I need to worry about
    >ground loops if I use the same serial port? (whine, whine, whine)
    >It's just hard to get the 486-DC fixed; know what I mean?


    You can sanity check the ground loop problem with a voltmeter.

    A scope would be a better tool for checking the PPS signal.
    A meter might show something, but I'd expect troubles from
    the long averaging times.

    You could also put the scope/meter on the input to the DCD pin
    to make sure you have an input rather than an output. It's
    probably pulled up to a few volts. Look at others to see
    what an output signal looks like.

    --
    The suespammers.org mail server is located in California. So are all my
    other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
    commercial e-mail to my suespammers.org address or any of my other addresses.
    These are my opinions, not necessarily my employer's. I hate spam.


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