Last Date | Back to Table | Next Date |
Data Points | Average Readability Index |
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144 | 3.42 |
Legend | |
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Dark Path | The period when it is dark at both the transmitting site in Ft. Collins, Colorado, and the receiving site. The 60 kHz WWVB signal is strongest during the dark path hours, so the period between the vertical green lines on the graph is the best time for reception. |
Top Graph | The top graph shows the measured field strength of WWVB at the monitoring site. The unit is microvolts per meter. |
Bottom Graph | The bottom graph shows the readability of the received signal.
The WWVB time code is sent at the very slow rate of 1 bit per second. A complete time code contains 60 bits
of information and requires a full minute to be sent. In order for a radio controlled clock (RCC) to
to synchronize, it must be able to successfully read and decode time code bits for at least a full minute, and many
products require at least two complete time codes to be read before they display the received time.
Fluctuations in the signal strength, even if the signal is strong, might make it impossible for a RCC to successfully decode the time.
Keep in mind that not all RCCs are created equal, some employ advanced digital signal processing techniques that will
allow them to synchronize under conditions where other products will fail.
The readability rating displayed in this column was designed to estimate whether or not a RCC will be able to synchronize. Keep in mind that these ratings only apply if your RCC is located in the same region of the country as the signal strength meter. The current signal readability rating can have one of four different values: Most products only attempt to synchronize at night when the readability conditions are generally Excellent or Very Good in most parts of the continental United States. If you cannot get your RCC to work during the daytime hours, it will still probably synchronize if you let it run overnight. |