1 - Unreadable - It is highly unlikely that a RCC will be able to synchronize right now, but conditions should improve later.2 - Intermittent - The conditions are not optimal, but a well designed RCC should still be able to synchronize.3 - Very Good - Most RCCs will be able to synchronize under these conditions.4 - Excellent - Nearly all properly functioning RCCs should be able to synchronize under these conditions.The current signal readability rating can have one of four different values: Keep in mind that these ratings only apply if your RCC is located in the same region of the country as the signal strength
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 not all RCCs are created equal, some employ advanced digital signal processing techniques that willĪllow them to synchronize under conditions where other products will fail. Products require at least two complete time codes to be read before they display the received time.įluctuations in the signal strength, even if the signal is strong, might make it impossible for a RCC to successfully decode the time.
#Wwvb radio full#
To synchronize, it must be able to successfully read and decode time code bits for at least a full minute, and many In order for a radio controlled clock (RCC) to Of information and requires a full minute to be sent. The WWVB time code is sent at the very slow rate of 1 bit per second. The bottom graph shows the readability of the received signal. The top graph shows the measured field strength of WWVB at the monitoring site. The graph is the best time for reception. The 60 kHz WWVB signal is strongest during the dark path hours, so the period between the vertical green lines on The period when it is dark at both the transmitting site in Ft. Leap year calculation was simple, and calculating the day of year was alsoĬalculating whether daylight savings time was in effect took a little bit moreĮffort.NIST: WWVB field strength and readability WWVB field strength and readability for However, the WWVB protocol required some extra date/time information notĭirectly available in the ZDA data, so I had to write some date/time conversion It was easy to parse the ZDA information to get the current date and time. Unfortunately, I can’t get my wristwatch to receive the 60 kHzĪmplitude-modulated time signal in my dorm room in Cambridge, Massachusetts. Theoretically, during goodĪtmospheric conditions, the signal should cover the continental United States. System with an effective radiated power of 70 kW. WWVB broadcasts from Fort Collins, Colorado, using a two-transmitter WWVB radio station, which continuously broadcasts official NIST US Most radio-controlled clocks in the United States are synchronized to the Neither gain nor lose one second in about 300 million years. Quartz clocks have a fractional inaccuracy δ f / f ≈ 6 × 1 0 − 6 \delta f / f \approx 6 \times 10^ δ f / f < 1 × 1 0 − 1 6, meaning that the clock would Radio clocks maintain time by using an internal quartzĬrystal oscillator and periodically synchronizing with an atomic clock radio Radio-controlled clocks that are synchronized to true atomicĬlocks. Most so-called atomic clocks aren’t true atomic clocks rather, they are
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