[time-nuts] WWV Clock

[Mike Monett]

  Brooke Clarke <brooke at pacific.net> wrote:

  > Hi Mike:

  > Note that  the  way a clock checks to see of it  has  received the
  > data correctly is to compare two adjacent frames and check  to see
  > that they differ by one minute.

  > If the  clock  was smart it would start to  listen  a  few minutes
  > prior to midnight and would recognize that there was going to be a
  > DST change at midnight.

  > If the  clock started at what it thought was midnight, but  it was
  > running a second slow then it would miss the first frame,  but the
  > next minute it would get the "new" frame and switch to/from DST.

  > I think your clock is just not receiving a good enough signal. The
  > key may be you need to mount the clock on a wall that's 90 degrees
  > from where it is now.

  > That's the  problem I had with an atomic clock,  ie  the loopstick
  > antenna has  deep  nulls  and   if   you  point  the  null  at the
  > transmitter . . . See:

  > http://www.prc68.com/I/Shadow-Clock.shtml#WT5360U

  > I like  the projection clock in my bedroom. No  glasses,  no light
  > needed to tell the time.

  >Have Fun,

  >Brooke Clarke
  >http://www.prc68.com

  Hi Brooke,

  Thanks for the note. As the paragraph in tech pub 432 says,

  "On the day of a change from ST to DST bit 57 changes from 0 to 1 at
  0000 UTC, and bit 58 changes from 0 to 1 exactly 24 hours  later. On
  the day  of a change from DST back to ST bit 57 changes from 1  to 0
  at 0000 UTC, and bit 58 changes from 1 to 0 exactly 24 hours later."

    <http://tf.nist.gov/timefreq/general/pdf/1383.pdf>

  As you  can  see, the first bit (57) changes at  0000  GMT. However,
  Eastern Standard Time starts 5 hours later, so all the radios in the
  US and  Canada already know the bit is set when they  start updating
  at their local midnight. The problem is this particular  brand seems
  to ignore bit 57, and only pays attention to bit 58.

  The clocks  are  mounted in two buildings  several  blocks  apart. I
  found the   optimum   location   for   each   by   forcing  a manual
  synchronization and picked the spot that gave the fastest sync.

  The bearing  to Fort Collins is around 270 degrees.  Both  walls run
  about 225  degrees,  or about 45 degrees from  the  desired bearing.
  Here is a picture of a loop with the desired orientation:

  <http://www.rescueelectronics.com/images/WWVB_Antenna_Diagram2.jpg>

  So the  actual  orientation is not ideal, but the  loop  has  a much
  flatter radiation  pattern  with a sharper  and  narrower  null than
  shown above, and the signal loss is not as bad as you might expect.

  As I  mentioned earlier, this brand has  excellent  sensitivity, and
  will usually synchronize manually starting around 5:00pm.  The proof
  is the clocks usually synchronize on the first attempt  at midnight,
  so improving the signal strength would not change the outcome.

  Since the clocks are about 45 degrees from full  broadside, changing
  the orientation by 90 degrees would not change the  signal strength.
  They would still be 45 degrees off the desired bearing. But they run
  fine and keep perfect time.

  Thanks for  the note on your projection clock. I  have  been looking
  for a silent WWVB clock with a lighted face for a long time, but had
  no luck. The WT-5360U looks like the perfect solution. I'll  get one
  on order right away.

  Best Regards,

  Mike Monett