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WWVB to Test Signal Improvement

NIST radio station to test adding phase modulation to AM carrier

NIST radio station WWVB(AM) is trying to improve its signal penetration.

The station near Fort Collins, Colo. continuously broadcasts time and frequency signals at 60 kHz. The carrier frequency provides a stable frequency reference traceable to the national standard. WWVB is also used for high level applications such as network time synchronization and frequency calibrations.

It will be interesting to see if those who tune in to set their clocks by the station notice an improvement while NIST conducts the tests this week.

WWVB will test a phase-modulated broadcast format beginning at 1900 UTC (1p.m. MDT) Thursday, June 14 and ending at 1800 UTC (noon MDT) on Friday, June 29.

“During the test period, the normal WWVB broadcast will be restored for a one-hour period onweekdays only,” according to WWVB broadcast manager John Lowe. “Radio-controlled clocks and watches will not be affected by the test. Phase-locking 60 kHz timing and frequency standard receivers may lose lock during the test, but will restore during the normal broadcast period,” he states on the WWVB website.

WWVB’s current power level is about 70 kW.

In theory, WWVB could improve its signal penetration by 14 dB if it added phase modulation to its existing amplitude modulated carrier. Devices designed to receive the PM will have at least a 14 dB advantage over the AM signal, Lowe told Radio World.

WWVB has already conducted experiments where phase modulation has been added to its AM signal for brief periods of time. For this new test, NIST will gather field data on the East Coast to better determine how much of the calculated 14 dB improvement is actually realized.