WWV is a shortwave ("high frequency" or HF) radio station, located near Fort Collins, Colorado. It has broadcast a continuous time signal since 1945, and implements United States government frequency standards, with transmitters operating on 2.5, 5, 10, 15, 20, and 25 MHz.Transmissions at 25 MHz were stopped in 1977 and resumed in 2014. WWV is operated by the U.S. National Institute of Standards and Technology (NIST), under the oversight of its Time and Frequency Division, which is part of NIST's Physical Measurement Laboratory based in Gaithersburg, Maryland. The letters WWV are only a call sign and do not stand for anything (see below).
WWV was established in 1919 by the Bureau of Standards in Washington, D.C., making it one of the oldest continuously-operating radio stations in the United States."What Closing A Government Radio Station Would Mean For Your Clocks" (transcript), Weekend Edition Saturday, August 25, 2018 (NPR.com) NIST celebrated WWV's centennial on October 1, 2019."NIST Radio Station WWV 100-year Anniversary" (NIST.gov)
In 1931, the station relocated to the first of three suburban Maryland sites, before moving to a location near Fort Collins in 1966. WWV shares this site with longwave (also known as "low frequency" or LF) station WWVB, which transmits carrier and time code (no voice) at 60 kHz. NIST also operates shortwave station WWVH on Kauai, Hawaii. Both WWV and WWVH announce the time of day each minute in Coordinated Universal Time, and make other recorded announcements of general interest on an hourly schedule, including the Global Positioning System (GPS) satellite constellation status. Because they simultaneously transmit on the same frequencies, WWV uses a male voice in order to differentiate itself from WWVH, which uses a female voice.
Service
Since 1945, WWV has disseminated "official U.S. time" provided by government entities NIST and the United States Naval Observatory (USNO), to ensure that uniform time is maintained throughout the United States and around the world. WWV provides a public service by making time information freely available at all hours.
The time signals generated by WWV allow time-keeping devices such as radio-controlled clocks, weather stations and wristwatches to automatically maintain accurate time without the need for manual adjustment. These time signals are used by commercial and institutional interests where accurate time plays a vital role in daily operations including shipping, transport, technology, research, education, military, public safety and telecommunications. It is of particular importance in broadcasting, whether it be commercial, public, or private interests such as amateur radio operators, who use the station's transmissions to test their equipment.
Transmission system WWV antenna coordinates (WGS84) 2.5 MHz 5 MHz 10 MHz 15 MHz 20 MHz 25 MHz
WWV broadcasts over six transmitters, each one dedicated to a single frequency. The transmitting frequencies and time signals of WWV, WWVB and WWVH, along with the four atomic (cesium) clocks from which their time signals are derived, are maintained by NIST's Time and Frequency Division, which is based in nearby Boulder, Colorado. WWVB's carrier frequency is maintained to an accuracy of 1 part in 1014 and can be used as a frequency reference. The broadcast time is accurate to within of UTC and of the national time standard.
The transmitters for 2.5 MHz and 20 MHz have an ERP of 2.5 kW, while those for the other three frequencies use 10 kW of ERP. (includes description of 25 MHz broadcast) Each transmitter has a dedicated antenna, with a height corresponding to one-half of its wavelength, and an omnidirectional signal radiation pattern. The top half of each antenna tower has a quarter-wavelength radiating element, and the bottom half uses nine guy wires, connected to the midpoint of the tower and sloped at one-to-one from the ground—with a length of times the wavelength—as additional radiating elements.
Telephone service WWV's time signal can be accessed by telephone by calling +1 (303) 499-7111 (WWV). Telephone calls are limited to 2 minutes, and the signal is delayed by an average of 30 milliseconds due to telephone network propagation time.
History Establishment
The earliest formal record of WWV's existence is in the October 1, 1919 issue of the Department of Commerce's Radio Service Bulletin, where it was listed as a new "experimental station""New Stations: Government Stations", Radio Service Bulletin, October 1, 1919, page 4. assigned to the Bureau of Standards in Washington, D.C., with the randomly issued call letters of WWV.WWV received its call letters from a block of call signs that the Department of Commerce, which regulated radio at this time, had issued to government stations—two months previously it assigned WWG, WWO, WWU, WWQ and WWX to five Post Office Department stations ("New Stations: Government Stations", Radio Service Bulletin, August 1, 1919, page 4). WWV is one of a small number of radio stations west of the Mississippi River with a call sign beginning with W instead of K, as the original call was kept when the station moved to Colorado. As a government station, WWV, does not fall within the FCC's jurisdiction with respect to call signs, and an FCC regulation reserves the call signs WWV, WWVB through WWVI, WWVL and WWVS for "standard frequency" stations ("Title 47:Subpart D:§ 2.302: Call Signs", Code of Federal Regulations, Government Printing Office). However, there were also earlier reports of radio demonstrations by the Bureau, starting the previous February."Awed Visitors Listen to 'Pretty Baby' Played by Wireless Phonograph", Washington Times, February 26, 1919, page 3."Music By Radio Now Fact" by J. Maell, Washington Times, July 31, 1919, page 15."An Almost Unlimited Field For Radio Telephony" section of "Bureau of Standards' Radio Work" by J. H. Dellinger, The Federal Employee, October 11, 1919, pages 592-593.
As of May 1920 the Bureau's Radio Laboratory was reported to be conducting weekly Friday evening concerts from 8:30 to 11:00, transmitting on 600 kHz."13 The Transmission of Music by Radio" by S. W. Stratton, Technical News Bulletin no. 38, Bureau of Standards, June 4, 1920, pages 8-9. That same month, the Bureau demonstrated a portable radio receiver, called the "portaphone", which was said to be capable of receiving broadcast programs up to away. A newspaper article the following August reported that the weekly concerts could be heard up to from Washington. It also noted that "The bureau has been experimenting with the wireless music for several months, and has reached such an advanced stage of development that further investigation to them is useless, and they are going to discontinue the concerts.""'Picking' Tunes From Air Nightly Pastime With Wireless Amateurs", Washington Times, August 8, 1920, page 26. However, the station continued to make occasional broadcasts, and in January 1921 a new distance record was announced when a listener in Chattanooga, Tennessee reported hearing the "jazzy waves whirling out from the Bureau of Standards"."Hear D.C. Radio Music in Tenn.", Washington Times, January 17, 1921, page 1.
On December 15, 1920, WWV began broadcasting 500-word "Daily Radio Marketgrams", prepared by the U.S. Bureau of Markets, in Morse code on 750 kHz, which reportedly could be heard up to from Washington."Daily Radio Marketgrams", The Wireless Age, April 1921, page 8. However, on April 15, 1921 responsibility for the reports was transferred to four stations operated by the Post Office Department, including its WWX in Washington, D.C."Radio Market News Service", QST, July 1921, page 24.
Standard frequency transmissions At the end of 1922, WWV's purpose shifted to broadcasting standard frequency signals. These were an important aid to broadcasting and amateur stations, because their equipment limitations at the time meant they had difficulty staying on their assigned frequencies. Testing began on January 29, 1923. Regularly scheduled operations began on March 6, 1923, consisting of seven transmitting frequencies ranging from 550 to kHz (wavelengths of 545 to 200 meters)."Bureau of Standards to Test Seven Standard Waves" by Carl H. Butman, Radio World, February 24, 1923, page 13. The frequencies were accurate to "better than three-tenths of one percent"."Radio Signals of Standard Frequency", Radio Service Bulletin, June 1, 1923, page 22. At first, the transmitter had to be manually switched from one frequency to the next, using a wavemeter. The first quartz resonators (that stabilized the frequency generating oscillators) were invented in the mid-1920s, and they greatly improved the accuracy of WWV's frequency broadcasts.
In 1926, WWV was nearly shut down. Its signal could only cover the eastern half of the United States, and other stations located in Minneapolis and at Stanford University and the Massachusetts Institute of Technology were slowly making WWV redundant. The station's impending shutdown was announced in 1926, but it was saved by a flood of protests from citizens who relied on the service. Later, in 1931, WWV underwent an upgrade. Its transmitter, now directly controlled by a quartz oscillator, was moved to College Park, Maryland. Broadcasts began on 5 MHz. A year later, the station was moved again, to Department of Agriculture land in Beltsville, Maryland. Broadcasts were added on 10 and 15 MHz, power was increased, and time signals, an A440 tone, and ionosphere reports were all added to the broadcast in June 1937.
WWV was nearly destroyed by a fire on November 6, 1940. The frequency and transmitting equipment was recovered, and the station was back on the air (with reduced power) on November 11. Congress funded a new station in July 1941, and it was built south of the former location, still referred to as Beltsville (although in 1961 the name used for the transmitter location would be changed to Greenbelt, Maryland). WWV resumed normal broadcasts on 2.5, 5, 10, and 15 MHz on August 1, 1943.
Time signal transmissions Beginning in 1913 the primary official time station broadcasting in the eastern United States was the Navy's NAA in Arlington, Virginia. NAA was decommissioned in 1941. WWV began broadcasting second pulses in 1937, but these were not initially synchronized to actual time. In June 1944, the United States Naval Observatory allowed WWV to use the USNO clock as a source for its time signals. Over a year later, in October 1945, WWV broadcast Morse code time announcements every five minutes. Voice announcements started on January 1, 1950, and were broadcast every five minutes. Audio frequencies of 600 Hz and 440 Hz were employed during alternating minutes. By this time, WWV was broadcasting on 2.5, 5, 10, 15, 20, 25, 30, and 35 MHz. The 30 and 35 MHz broadcasts ended in 1953.
A binary-coded decimal time code began testing in 1960, and became permanent in 1961. This "NASA time code" was modulated onto a kHz audio tone at 100 Hz, sounding somewhat like a monotonous repeated "baaga-bong". The code was also described as sounding like a "buzz-saw". On July 1, 1971, the time code's broadcast was changed to 100 Hz subcarrier, which is inaudible when using a normal radio (but can be heard using headphones or recorded using a chart recorder).
WWV moved to a location near Fort Collins on December 1, 1966, Also contains details about the construction of the WWV transmitters. enabling better reception of its signal throughout the continental United States. WWVB had signed on in that location three years earlier. In April 1967, WWV stopped using the local time of the transmitter site (Eastern Time until 1966, and Mountain Time afterwards) and switched to broadcasting Greenwich Mean Time or GMT. The station switched again, to Coordinated Universal Time (UTC), in 1974.