Notice of Change in WWVB Modulation Depth
The 60 kHz WWVB time code broadcast changed the modulation depth from 10 to 17 dB on July 12, 2005 at 0000 UTC. This was done to improve the performance of WWVB radio controlled clocks. Click here for a short technical paper that discusses the subject of increasing the modulation depth (PDF file).
During normal operation, the 60 kHz signal from WWVB is transmitted 24 hours per day, 7 days a week. The table includes periods since January 1, 2005 when the signal was off or intermittent for more than 5 minutes.
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