[time-nuts] WWV Clock

Mike Monett xde-l2g3 at myamail.com
Mon Nov 2 08:50:35 UTC 2009


  "Majdi S. Abbas" <msa at latt.net> wrote:

  > On Sun,  Nov  01, 2009 at 05:51:24PM  -0500,  Glenn  Little WB4UIV
  > wrote:

  >> My WWV clock at home and the master clock at the TV  station that
  >> I am engineer for did not update to EST from EDT.

  >> Did anyone else see their WWV clock not change time for DST?

  > WWVB does  have  a  bit that accounts for it,  but  most  of those
  > clocks just  try to update once a day, and if they  take  a single
  > bit error in the minute or two they check, they'll miss it.

  [...]

  >	Majdi, N0RMZ

  I don't  know if WWV receivers work this way, but WWVB  clocks start
  looking at midnight and repeat every hour until 06:00, or until they
  get a  valid signal. Once they update, they no longer  look  for the
  time signal until the next midnight.

  If the signal is strong enough to update at midnight, the clock will
  miss the  time  change at 2:00 am. So they will be off  by  one hour
  until the next update.

  In this  case,  the problem is not due to a  weak  signal  causing a
  single bit error, it is due to a strong signal and receiving all the
  bits correctly on the first attempt.

  In my  case,  the GCD distance between Toronto and  Fort  Collins is
  1333 miles  (2144  km, 1158 nautical miles),  and  the  direction is
  269.6 degrees: <http://www.indo.com/distance/>

  The NIST  WWVB Coverage maps show the signal in Toronto  is  good at
  0000UTC, and  the  receiver will probably synchronize  on  the first
  attempt at midnight (0500UTC):

    <http://tf.nist.gov/stations/wwvbcoverage.htm>

  So all  my WWVB clocks missed the time change on the first  day. For
  reference, the  clocks are HTAWI HAA-1203W 12"  White  Atomic Analog
  Wall Clock:

    <http://www.partshelf.com/ps-haa-1203w.html>>

  They have  been  on  sale for $14.95 for several  years,  and  I can
  recommend them highly. Good styling, very economical,  and excellent
  reception. When  I  first  got  them,   I  was  amazed  to  see them
  synchronize at  5:00pm local time when the signals are very  weak in
  Toronto. The  only  problem is they make a loud  tick  every second,
  which is the same as any digital clock movement. One day I will take
  them apart and put a small resistor and speedup capacitor  in series
  with the motor to quiet them.

  Regards,

  Mike Monett



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