WWVH
Encyclopedia
National Institute of Standards and Technology
The National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory, otherwise known as a National Metrological Institute , which is a non-regulatory agency of the United States Department of Commerce...
's shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
time signal
Time signal
A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day.-Audible and visible time signals:...
station in Kekaha
Kekaha, Hawaii
Kekaha is a census-designated place in Kauai County, Hawaii, United States. The population was 3,175 at the 2000 census.-History:...
, on the island of Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
in the state of Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
.
WWVH is the Pacific sister station to WWV, and has a similar broadcast format. Like WWV, WWVH's main function is the dissemination of official U.S. Government time, through exactly the same methods as found on WWV's signal.
To minimize interference with the WWV broadcasts on the same frequencies, WWVH's broadcasts on 5, 10 and 15 MHz are directional, pointed primarily west. Despite this strategy, in certain places, particularly on the west coast of North America; and at certain times, due to ionospheric
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
conditions, the listener can actually hear both WWV and WWVH on the same frequency at the same time. The information modulated on the carrier is modified to reduce confusion if both are received simultaneously. In particular, voice announcements on one correspond to silent periods on the other.
Transmission system
WWVH broadcasts its signal on four transmitters, one for each frequency. The 2.5 MHz transmitter puts out an ERPEffective radiated power
In radio telecommunications, effective radiated power or equivalent radiated power is a standardized theoretical measurement of radio frequency energy using the SI unit watts, and is determined by subtracting system losses and adding system gains...
of 5 kW, while the other transmitters use 10 kW of ERP. The 2.5 MHz antenna is one half-wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
tall, and radiates in an omnidirectional pattern. The remaining antennas each consist of two elements one half-wavelength tall and horizontally separated by one quarter-wavelength. The signal radiating from one element is in quadrature phase with respect to the signal from the other. This results in a cardioid
Cardioid
A cardioid is a plane curve traced by a point on the perimeter of a circle that is rolling around a fixed circle of the same radius. It is therefore a type of limaçon and can also be defined as an epicycloid having a single cusp...
radiation pattern with a maximum gain directed west.
Broadcast Format
- The 5 ms second ticks are 6 cycles of 1200 Hz rather than 5 cycles of 1000 Hz. The 800 ms minute beep is also 1200 Hz. (Like WWV, this is omitted during minutes 29 and 59, and changed to 1500 Hz at the top of each hour.)
- The voice announcements use a female voice (that of Jane BarbeJane BarbeJane Barbe was an American voice actress known as the "Time Lady" for the recordings she made for the Bell System and other phone companies. The ubiquity of her recordings eventually made her a pop-culture figure whose death drew national attention....
) and last 7.5 seconds starting 15 seconds before the minute. (WWV broadcasts in a male voice during the last 7.5 seconds of each minute.) - The audio tones sent during the first 45 seconds of most minutes are swapped: 600 Hz is played during even minutes, and 500 Hz is played during odd minutes. (Receiving both simultaneously gives the listener a sound similar to a continuously-ringing chime.)
- The A440A440 (Concert A)A440 is the musical note A above middle C. It has a frequency of 440 Hz and serves as a general tuning standard for musical pitch.Prior to the standardization on 440 Hz, many countries and organizations followed the Austrian government's 1885 recommendation of 435 Hz...
tone marking the hour is sent during minute 1 (as opposed to minute 2 for WWV). Like WWV, it is omitted during the first hour of each UTC day. - The audio tones are suppressed while WWV is transmitting voice announcements: minutes 00, 08–10, 14–19, and 30.
- The voice announcements are rescheduled relative to WWV:
- Station identification is made during minutes 29 and 59 (vs. 00 and 30)
- GPS satellite health reportsNotice Advisory to NAVSTAR UsersA notice advisory to NAVSTAR users, or NANU, is a message issued jointly by the United States Coast Guard and the GPS Operations Center at Schriever Air Force Base in Colorado. NANUs provide updates on the general health of individual satellites in the GPS constellation...
are transmitted during minutes 43 and 44 (vs. 14 and 15) - NOAANational Oceanic and Atmospheric AdministrationThe National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
space weather geoalerts are transmitted during minute 45 (vs. 18) - National Weather ServiceNational Weather ServiceThe National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
storm warnings for all sections of the Pacific ocean are broadcast during minutes 48–51, overflowing to minute 52 when necessary (vs. Atlantic and northeast Pacific information during 08–10 and 11). - Minutes 03 and 47 are used for NIST special announcements when necessary (vs. 04 and 16).