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    Re: Radio time signals disappear
    From: Paul Hirose
    Date: 2018 Aug 14, 14:50 -0700

    On 2018-08-13 22:15, Sean C wrote:
    > According to Casio's website, the module (or the guts) of my favorite 
    "atomic" watch indeed uses WWVB - as do most clocks and watches. That's a 
    relief, thank you!
    I wouldn't feel too relieved. The 2019 budget request simply says "the
    shutdown of NIST radio stations in Colorado and Hawaii." WWVB is in
    Colorado, at the WWV site.
    Maybe WWV and WWVH will shut down, but WWVB will remain on the air.
    NIST has a page on the approaching 100th anniversary of WWV (October
    2019), including a countdown timer:
    Personally, termination of WWV and WWVH would be a loss. I use those
    stations to check my watches and record their errors. One watch has a
    continuous record going back to 2000! For this purpose an aural time
    signal is more convenient and accurate than visual.
    Phone audio from WWV (303-499-7111) or USNO (719-567-6742) is more
    reliable than the shortwave signal, which can be exasperating when weak
    and fading. But the audio seems to be delayed 1/4 second on my cell
    phone. Since I estimate watch error to the nearest 1/4 second, that's
    significant. I'd use the phone if the delay were guaranteed constant,
    but of course it's not.
    The time display on my phone itself is about 1/2 second slow.
    On the other hand, the little clock at the side of the USNO pages has
    been exactly "on the tick" every time I checked. All those accuracy
    evaluations are possible thanks to a cheap shortwave receiver and
    WWV/WWVH. If they go off the air I lose my gold standard.
    My "good receiver" (Winradio Excalibur) is not as good for this purpose.
    The physical part of the radio (about the size and shape of a paperback
    novel) digitizes the RF input and feeds it via USB to the computer,
    where the radio software processes the data into audio. Data takes about
    1/4 second to traverse the pipeline, so the tick is always late.
    However, the extremely sharp passband filtering enables some
    entertaining tricks with WWV. For instance, the radiated signal carries
    1 Hz data on a 100 Hz subcarrier. If reception is good you can hear this
    on any radio as the pulsing hum that shadows the seconds ticks.
    With an Excalibur, select 50 Hz bandwidth and tune 100 Hz above or below
    the carrier in CW mode to receive the subcarrier as if it were a Morse
    signal. The pulses can be copied by hand and decoded with the chart in
    Wikipedia (which is better than the official chart at the NIST site).
    The carrier is 100 Hz away but you hear only a faint heterodyne thanks
    to the narrow bandwidth. Voice announcements are a barely audible
    scratching sound.
    It is sadly ironic that affordable receivers with such performance have
    arrived, but shortwave spectrum is barren compared to what I heard as a
    teen with a Radio Shack DX-150.
    Someone mentioned RWM and BPM. I heard them as kid with my DX-150, but
    they don't come in where I live now. The present state of the ionosphere
    and my indoor antenna don't help. I have a dim memory that one of those
    stations used to transmit UT1, not UTC. The ticks were obviously out of
    sync with WWV.

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