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improving WWVB reception

Discussion in 'Electronic Repair' started by Chris Campbell, Aug 4, 2003.

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  1. I recently bought this clock:

    http://store.yahoo.com/atomictime/attimsildigw.html

    for use in a radio studio. We're going to do a fancier timekeeping
    solution after our studio move next year but for now this is good
    enough.

    Well, it would be if it worked. The clock synchronizes with WWVB
    every night, and I had it working on my engineering bench. But with
    it mounted on my air studio wall, it won't sync. I've tried three
    different positions -- mounted flat on west, north and east walls. In
    each position, I left it there for about a week to see if it would
    sync.

    I'm in Atlanta, so WWVB is generally west from me. I don't know how
    the internal antenna element is oriented, but I assume it's parallel
    to the big flat dimension of the clock, so either east or west should
    have worked best. Obviously the building is attenuating the signal,
    but I really want it to work in that room, so I've got to find a way
    to improve the signal reception without moving the clock much from
    where it's at.

    So, does anyone have any experience with opening these clocks up and
    adding an antenna? What kind of antenna should I use, and how should
    I orient it?

    - Chris
     
  2. Jerry G.

    Jerry G. Guest

    I have a GE clock that is very good. It is also using WWV. These
    clocks generally scan the base frequencies and lock in on the best of
    them.

    Your problem is that in your studio, the unit is not seeing the signal,
    which I realize is also your conclusion. It is possible to open the
    radio, and add on an antenna wire of some sort. If the signal is not
    present in your location, all you will add is noise in to its front end.

    You would have to work out the front end circuit of the clock receiver,
    to determine the best place to pick off to put a piece of wire to act as
    a simple antenna. The only drawback is that soldering to the circuit,
    you may also detune it a bit because of the stray capacitance of the
    added antenna wire, and also the soldering itself. There is no added RF
    input amplifier stage to offer isolation to the front end for any
    external antenna connection.

    It would be recommended in any case to put a capacitor of about 47 pF in
    series with the added wire at the antenna solder point. This is to give
    DC isolation. The 47 pF will easily pass frequencies from 5 mHz to 20
    mHz which is the scanning range of these clocks.

    The front end of these clocks are using MosFet devices. If there is any
    static electricity, this can cause damage. Care must be taken to not
    touch the bare end of the wire with the fingers. Use insulated wire
    only. A small gauge of about AWG 22 to AWG 26 stranded wire should be
    adequate. A length of about 6 to 10 feet should be okay.

    If all of this detunes the front end due to having no input isolation,
    then the reception will infact be worsened.

    If you want something very good. Leitch, and Torpey Time make
    professional clock systems that are designed to work from GPS. There
    are a number of other companies that also make these. You put up a
    small antenna about the size of a large donut in an area where it can
    see the sky. There is a 52 ohm foam coax cable that runs back to the
    clock receiver. The receiver has a digital packet output to run studio
    type clocks. The output time accuracy is in the parts per trillion. As
    a starter you need the receiver, antenna, cable, and 1 clock display
    module.

    At the TV station, we are using the Torpey system for our precision time
    keeping. This one is excellent.

    Check out:
    http://www.oakwoodbroadcast.com/Clocks_Timers/Torpey/torpey_gps1.html


    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    ==============================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    Instruments http://www.zoom-one.com/glgtech.htm
    ==============================================
    I recently bought this clock:

    http://store.yahoo.com/atomictime/attimsildigw.html

    for use in a radio studio. We're going to do a fancier timekeeping
    solution after our studio move next year but for now this is good
    enough.

    Well, it would be if it worked. The clock synchronizes with WWVB
    every night, and I had it working on my engineering bench. But with
    it mounted on my air studio wall, it won't sync. I've tried three
    different positions -- mounted flat on west, north and east walls. In
    each position, I left it there for about a week to see if it would
    sync.

    I'm in Atlanta, so WWVB is generally west from me. I don't know how
    the internal antenna element is oriented, but I assume it's parallel
    to the big flat dimension of the clock, so either east or west should
    have worked best. Obviously the building is attenuating the signal,
    but I really want it to work in that room, so I've got to find a way
    to improve the signal reception without moving the clock much from
    where it's at.

    So, does anyone have any experience with opening these clocks up and
    adding an antenna? What kind of antenna should I use, and how should
    I orient it?

    - Chris
     
  3. You may have a RFI problem. The 60KHz signal is pretty weak compared to a
    lot of the signals floating around in the average civilized office. Light
    dimmers, flourescent lights, CRT's, switching-mode power supplies all put
    out lots of RF in that part of the spectrum. Your best bet might be to just
    receive WWV on a SW radio and use it to set your clocks. Low-tech but
    usually works, unless propagation is just shot.
     
  4. There are some hints at the NIST website. I live in Florida and the
    nighttime signal is much better than the daytime signal. This is also true
    for Atlanta, but not as much variation as at my location. One thing that
    helps (sometimes) is to move the clock away from TV receivers and monitors.
    A 60 kHz antenna is a large beast, so there is nothing simple that you can
    do in that department.
     
  5. Tweetldee

    Tweetldee Guest

    I have two of those "atomic" clocks, one at home and one at work. Both came
    with admonitions in the instruction sheet to keep them at least 10 feet away
    from any computers, monitors or TV sets. Naturally, all of these items
    generate intense EMI fields around them and would swamp the weak 60KHz
    signal from WWVB.
    Unless you can satisfy these criteria, or provide an external antenna that
    you could couple to the internal antenna of your "atomic" clock, then I'm
    afraid you've a couple of boat anchors on your hands. Your clocks can only
    syncronize if they have a signal that is strong enough to allow it to
    receive the coded information that it needs to set the clock. Antenna
    placement is critical for these clocks.

    --
    Tweetldee
    Tweetldee at att dot net (Just subsitute the appropriate characters in the
    address)

    Time is what keeps everything from happening all at once.
     
  6. Bob M.

    Bob M. Guest

    I have several of these clocks at my house, including some atomic watches.
    No problem (luckily) but the antennas aren't really that big, especially
    inside the watch.

    Someone suggested I could take another loopstick antenna and put it outside,
    then run some wires back to the clock inside and wrap a few turns of the
    wire around the clock's antenna. I would think that some tuning would be
    necessary to get it to work well. I want to install a clock at a well
    shielded radio station transmitter building and short of putting the entire
    clock outside, I'm also running out of options.

    Bob M.
    ======
     
  7. ejxit

    ejxit Guest

    Since you have a location where the clock works, why not put a small light on it
    and point a small wireless camera at it. Then you can monitor the time almost
    anywhere in the building. I have atomic clocks in my home and they only work in
    2 west facing areas, so I know what your dealing with.
     
  8. Jerry, WWVB only operates at 60 KHz, while WWV is on the higher
    frequencies. you can not scan and lock on the best signal when there is
    only one signal.

    --


    Its August 5, 2003, so I'm 51 today!
    Michael A. Terrell
    Central Florida
     
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