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Enhanced WWVB Broadcast Format Change

Since October 29, 2012 at 1500 UTC (9:00 AM MDT), NIST Radio Station WWVB has been broadcasting a phase modulation (PM) time code protocol that has been added to the legacy AM/pulse-width-modulation signal. This enhancement to the broadcast, which has been tested throughout 2012, provides significantly improved performance in new products that are designed to receive it. Existing radio-controlled clocks and watches are not affected by this enhancement, and continue to work as before. A detailed technical description of the new format can be found here.

Disciplined oscillator products that track and lock to the 60 kHz WWVB carrier and were designed to work as frequency standards, will not work with the PM signal and will now become obsolete. A few radio controlled clocks that used information from the carrier – specifically the Spectracom NetClock and receivers manufactured by True Time during the 1970s and 1980s – will no longer be able to read the time code and will also be obsolete. For more information, contact Broadcast Manager John Lowe at or 303-497-5453.

Broadcast Outages for WWVB

 WWVB Home 2003 Outages2004 Outages 2005 Outages2006 Outages 2007 Outages2008 Outages 2009 Outages

2010 Outages 2011 Outages 2012 Outages 2013 Outages 2014 Outages2015 Outages2016 Outages2017 Outages

During normal operation, the 60 kHz signal from WWVB is transmitted 24 hours per day, 7 days a week. The table includes periods when the signal was off or intermittent for more than 5 minutes.

Date MJD Began (UTC) Ended (UTC)

7 February 2016