Brooke Clarke <bro...@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 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
