US Naval Observatory Master Clock

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Thread: US Naval Observatory Master Clock

  1. #1

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    US Naval Observatory Master Clock

    I got thinking recently about a particular public radio network that until recently still signed off for 3-4 hours nightly...at the time I think it was the last NPR station(s) that regularly signed off (that I'm aware of).

    Anyhow, after the sign off message, they started broadcasting the time, not from WWV/WWVH, but from the USNO's Master Clock. It remained on for about 5 minutes until power was shut off.

    The big question I have is where would this network have gotten a nonstop feed of the USNO's Master Clock? I am aware of the phone numbers for WWV/WWVH and USNO, along with hams running WWV internet streams, but those calls are limited to about 2 minutes and none are radio-grade audio quality
    As we used to say down in ol' Mexico City...A.M.F.!

  2. #2
    Quote Originally Posted by seattlesarchiebunker View Post
    I got thinking recently about a particular public radio network that until recently still signed off for 3-4 hours nightly...at the time I think it was the last NPR station(s) that regularly signed off (that I'm aware of).

    Anyhow, after the sign off message, they started broadcasting the time, not from WWV/WWVH, but from the USNO's Master Clock. It remained on for about 5 minutes until power was shut off.

    The big question I have is where would this network have gotten a nonstop feed of the USNO's Master Clock? I am aware of the phone numbers for WWV/WWVH and USNO, along with hams running WWV internet streams, but those calls are limited to about 2 minutes and none are radio-grade audio quality
    The Public Radio Satellite System (PRSS) uses USNO master clock audio as filler when one of its streams doesn't otherwise have audio on it. It was almost certainly coming from a PRSS receiver.
    All kinds of good stuff over at http://www.fybush.com

  3. #3
    Quote Originally Posted by seattlesarchiebunker View Post
    The big question I have is where would this network have gotten a nonstop feed of the USNO's Master Clock?
    They have a direct feed from USNO.

  4. #4
    Quote Originally Posted by TheBigA View Post
    They have a direct feed from USNO.
    At KCSN I regularly aired the U.S. Naval Observatory Master Clock man whom I called 'Bob the Time Guy'.

  5. #5

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    Quote Originally Posted by Hot Hits View Post
    At KCSN I regularly aired the U.S. Naval Observatory Master Clock man whom I called 'Bob the Time Guy'.
    Iím glad to hear that Jefferson Public Radio wasnít the only one to run it...the USNO clock is about as close as we Yanks can get to ďThe PipsĒ.

    Considering all the other countries that still run a TOH clock reminder, (including CBC Radio One at 1pm), Iím surprised it never really caught on here. Now with cellphones having pretty darned accurate clocks that are regularly synchronized by the cell sites, the days of watches or reminding listeners the exact time are slowly fading away.
    As we used to say down in ol' Mexico City...A.M.F.!

  6. #6

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    Quote Originally Posted by seattlesarchiebunker View Post

    Considering all the other countries that still run a TOH clock reminder, (including CBC Radio One at 1pm), I’m surprised it never really caught on here. Now with cellphones having pretty darned accurate clocks that are regularly synchronized by the cell sites, the days of watches or reminding listeners the exact time are slowly fading away.
    That "exact" time concept can be an interesting topic, depending on how accurate one needs to be.

    Since you mentioned cell phone time synchronization by the cell network, I wonder if that is perhaps also a function of the phone itself. My iPhone 6 seems to be very close to USNO, while my Nokia N95, a much older phone, is about 35 seconds slow.

    I also called USNO by my cell phone and the Vonage VoIP and there isn't any significant path delay difference between the two calls - there was a minor offset between the two circuits, just enough that I could tell the audio wasn't exactly in phase.

    Making "exact" time another concern is with satellite propagation times, the uplink and downlink paths - satellite circuit latency. This usually isn't an issue in program distribution but can be quite annoying for telephone calls which use one or more satellite links. Yes, probably not much of a problem today.

    Normally, program circuit latency shouldn't be much of an issue, if relatively constant, for say program switching or similar, and generally the listener or viewer doesn't care, unless the circuit latency results in (generally video) talent waiting for the studio to cue the talent and then the return latency for the talent audio/video to get back to the studio.

    In an anecdotal observation, it was New Year's eve 2016, and we were watching the New York ball drop and I realized by the time the program was on the TV, it was about 15 seconds late, per my precisely calibrated Casio watch, checked against the USNO. I can only guess that some of it was a profanity delay for the live programming, but some of it had to be associated with one or more satellite links between the source location and the eventual distribution via satellite to the home location.

    Exact time but off by 15 seconds.







    An interesting discussion on time concerns with the GPS constellation is at:

    https://www.nist.gov/pml/time-and-fr...-time-transfer

  7. #7
    Quote Originally Posted by RadioFan2J3 View Post
    ... In an anecdotal observation, it was New Year's eve 2016, and we were watching the New York ball drop and I realized by the time the program was on the TV, it was about 15 seconds late, per my precisely calibrated Casio watch, checked against the USNO. ...
    HDTV broadcast programming has a delay of about 15 seconds from real time, due to the encoding algorithm used to generate/transmit its digital waveform.

    HD/IBOC radio transmission also has a built-in delay.

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