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Offline thedoc

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Radio Controlled Clocks
« on: 04/12/2007 11:21:54 »
I have two radio-controlled speaking clocks that are identical but one’s two year’s older than the other. They speak at different times. Why is that?
Asked by David, Harlow

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« Last Edit: 04/12/2007 14:29:10 by BenV »


 

Offline thedoc

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Re: Question from the show - Radio Controlled Clocks
« Reply #1 on: 04/12/2007 11:21:54 »
We're actually not sure about this one!
Most radio-controlled clocks update themselves once a day, but cann't do so if they can't receive a strong enough radio signal.  It's possible that one of the clocks has a weaker antenna, and so isn't receiving a signal, and has fallen out of time.
Please let us know if you can think of any other reason for this!
 

paul.fr

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Re: Question from the show - Radio Controlled Clocks
« Reply #2 on: 04/12/2007 14:08:31 »
I assume the clocks are in different rooms, if this is so, then possibly the signal is being lost as it goes through the extra walls...or if the second radio is in a room near an outside(metal) garage, this may interfere with the signal!!!
 

paul.fr

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Question from the show - Radio Controlled Clocks
« Reply #3 on: 04/12/2007 17:52:30 »
He could always do the experiment, swap the clocks around and see if this changes which clock speaks first. This would give plenty of information, no matter what the result was.
 

Offline techmind

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Question from the show - Radio Controlled Clocks
« Reply #4 on: 04/12/2007 22:22:38 »
Most radio-controlled clocks have a button you can press to force them to receive the signal "on-demand" (it usually takes about 3 minutes). Normally the clock display shows whether this was successful or not.

Note also that such clocks use an internal ferrite rod antenna, which is directional, to receive the time signal. Consequently the orientation of the clock may also affect whether it can receive the signal or not. If a clock "looses" the radio-signal, it will gradually drift out of time like any other ordinary clock.

The UK time signal used to be transmitted from Rugby, but in the spring of this year (1st April 2007) was relocated to Anthorn in Cumbria (near the Scottish border). Consequently the signal-strength in the south of the UK is weaker than it used to be and so reception may now be more marginal in Harlow.

See also:
http://en.wikipedia.org/wiki/Time_from_NPL

The NPL have a page about "Common Clock Problems" at http://www.npl.co.uk/server.php?show=ConWebDoc.1002
- it's probably particularly worth making sure your clocks are not close to sources of interference like fluorescent or low-energy lightbulbs if they will be switched on at the time of day the clock synchronises itself (see the clock instructions)
« Last Edit: 04/12/2007 22:46:40 by techmind »
 

another_someone

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Question from the show - Radio Controlled Clocks
« Reply #5 on: 05/12/2007 02:15:43 »
How far apart are the times?

The question seems to refer to the clocks speaking at different time, but does not indicate they show different time - although it neither explicitly suggests that they show the same time, but it does seem something of a significant oversight to mention they speak at different time but not to mention they actually show different times.
 

paul.fr

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Question from the show - Radio Controlled Clocks
« Reply #6 on: 05/12/2007 23:30:40 »
Andrew, what band would the transmitted frequency be?
 

another_someone

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Question from the show - Radio Controlled Clocks
« Reply #7 on: 06/12/2007 01:04:51 »
The web page referenced states that the MSF signal in the UK is at 60KHz.

http://en.wikipedia.org/wiki/Radio_clock#Longwave_and_shortwave_transmissions
Quote
Time signals that can be used as references for radio clocks include:
    * U.S. NIST Broadcasts:
  • Longwave radio station WWVB at 60 kHz (binary coded decimal only) at 50 kW
  • Shortwave radio station WWV (a male voice, Fort Collins, Colorado, about 100 km north of Denver at approximately [show location on an interactive map] 40°40′49″N, 105°02′27″W) at 2.5, 5, 10, 15 and 20 MHz at 2.5 kW to 10 kW. This voice signal is available by telephone at 1-303-499-7111.

Time signals that can be used as references for radio clocks include:

    * U.S. NIST Broadcasts:
  • Longwave radio station WWVB at 60 kHz (binary coded decimal only) at 50 kW
  • Shortwave radio station WWV (a male voice, Fort Collins, Colorado, about 100 km north of Denver at approximately [show location on an interactive map] 40°40′49″N, 105°02′27″W) at 2.5, 5, 10, 15 and 20 MHz at 2.5 kW to 10 kW. This voice signal is available by telephone at 1-303-499-7111.
  • Shortwave radio station WWVH (a female voice, on Kauai near Kekaha, Hawaii, at about [show location on an interactive map] 21°59′16″N, 159°45′50″W) at 2.5, 5, 10, and 15 MHz at 2.5 kW to 10 kW
  • German Broadcasts: A time signal from DCF77 (Mainflingen, a transmitter near Frankfurt at 50 kW at about [show location on an interactive map] 50°01′N, 9°00′E) can be received on 77.5 kHz to a range of about 2000 km
  • Canadian Broadcasts: The official time can be obtained by tuning to radio station CHU (Ottawa, Ontario) at 3.33, 7.335 and 14.67 MHz, with FSK digital time data sent once per minute at 300 baud
  • UK Broadcasts: A time signal from MSF, an atomic clock near Anthorn (which was relocated from Rugby on 2007-04-01) can be received on 60 kHz

    * The JJY radio stations in Japan on 40/60 kHz
    * The BPM radio station in Xi'an, China at 2.5, 5, 10 and 15 MHz
    * Swiss Broadcasts: The legal Swiss time can be picked up from the HBG longwave transmitter in Prangins on 75 kHz. The time code is compatible with that of the German DCF-77 transmitter.
    * French Broadcasts: Station TDF transmits timecodes on 162 kHz from a site near Allouis
Shortwave radio station WWVH (a female voice, on Kauai near Kekaha, Hawaii, at about [show location on an interactive map] 21°59′16″N, 159°45′50″W) at 2.5, 5, 10, and 15 MHz at 2.5 kW to 10 kW
    * German Broadcasts: A time signal from DCF77 (Mainflingen, a transmitter near Frankfurt at 50 kW at about [show location on an interactive map] 50°01′N, 9°00′E) can be received on 77.5 kHz to a range of about 2000 km
    * Canadian Broadcasts: The official time can be obtained by tuning to radio station CHU (Ottawa, Ontario) at 3.33, 7.335 and 14.67 MHz, with FSK digital time data sent once per minute at 300 baud
    * UK Broadcasts: A time signal from MSF, an atomic clock near Anthorn (which was relocated from Rugby on 2007-04-01) can be received on 60 kHz
    * The JJY radio stations in Japan on 40/60 kHz
    * The BPM radio station in Xi'an, China at 2.5, 5, 10 and 15 MHz
    * Swiss Broadcasts: The legal Swiss time can be picked up from the HBG longwave transmitter in Prangins on 75 kHz. The time code is compatible with that of the German DCF-77 transmitter.
    * French Broadcasts: Station TDF transmits timecodes on 162 kHz from a site near Allouis
[/list]
 

Offline kdlynn

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Question from the show - Radio Controlled Clocks
« Reply #8 on: 06/12/2007 01:31:06 »
i went to the place in denver. you can go in usually and see the clocks, but they were closed.
 

paul.fr

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Question from the show - Radio Controlled Clocks
« Reply #9 on: 06/12/2007 03:52:24 »
Thanks George, i guessed it was either lw or mw, but it's always nice to know rather than guess
 

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Question from the show - Radio Controlled Clocks
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