In April 1960, WWVL broadcast began with 1,000 times more stable reception at a distance than WWV or WWVH had been received.
So in 1962 construction began north of Fort Collins, Colorado. The new site would consolidate all NBS continental broadcasts with the VLF (20 kHz) and LF (60 kHz) to be built first.
And on July 5, 1963, WWVB radiating at 7 kW - soon 13 kW - began broadcasting and in August WWVL began broadcasting.
The time and frequency of the broadcasts were controlled by Boulder Labs with a 50 MHz signal sent from the time scale in Boulder.
The new LB broadcast used an amplitude (level shift) modulation and a binary code shift to encode time information.
By 1966, the WWV portion of the Fort Collins construction was complete. And on December 1, 1966, at 0 hour GMT (5 p.m. November 30th local time) all the WWV signals began broadcasting at the new station simultaneously - all signals at Greenbelt, Maryland were shut off.