Antennas
| WWVB antenna helix house coordinates (WGS84) | |
|---|---|
| North | 40°40′50.6″N 105°03′01.7″W / 40.680722°N 105.050472°W / 40.680722; -105.050472 (WWVB - North antenna) |
| South | 40°40′28.9″N 105°02′42.3″W / 40.674694°N 105.045083°W / 40.674694; -105.045083 (WWVB - South antenna) |
Coordinates: 40°40′41″N 105°02′49″W / 40.67806°N 105.04694°W / 40.67806; -105.04694 (WWVB - Transmitter building)
The WWVB signal is transmitted via a phased array of two identical antenna systems, spaced 857 meters (2,810 ft) apart, one of which was previously used for WWVL. Each consists of four 122-meter (400 ft) towers that are used to suspend a "top-loaded monopole" (T-aerial), consisting of a diamond-shaped "web" of several cables in a plane (a capacitive "top-hat") supported by the towers, and a downlead (vertical cable) in the middle that connects the top-hat to a "helix house" on the ground. In this configuration, the downlead is the radiating element of the antenna. Each helix house contains a dual fixed-variable inductor system, which is automatically matched to the transmitter via a feedback loop to keep the antenna system at its maximum radiating efficiency. The combination of the downlead and top-hat is designed to replace a single, quarter-wavelength antenna, which, at 60 kHz, would have to be an impractical 1,250 meters (4,100 ft) tall.
As part of a WWVB modernization program in the late 1990s, the decommissioned WWVL antenna was refurbished and became part of the current phased array. Using both antennas simultaneously resulted in an increase to 50 kW (later 70 kW) ERP. The station also became able to operate on one antenna, with an ERP of 27 kW, while the other is being maintained.
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