National Institute of Standards and Technology radio station WWVB(AM), near Fort Collins, Colo., is conducting another phase-modulated broadcast test beginning at 11 a.m. Pacific on Tuesday, Sept. 4.
The tests are due to end at 11 a.m. Pacific on Thursday, Sept. 6.
WWVB is the station that many radio-controlled clocks in North America use to synchronize themselves.
NIST engineers have been testing adding phase modulation to the AM carrier to improve the signal’s coverage area.
During the test period, the broadcast will be randomly switched between the normal (AM modulated) WWVB broadcast and the new format with phase-modulation added.
Radio-controlled clocks and watches should not be affected, according to WWVB broadcast manager John Lowe.
Phase-locking 60 kHz timing and frequency standard receivers may lose lock during the test, but will restore during the normal broadcast periods.