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Time Signal Information from Pub CHAPTER 2 RADIO TIME SIGNALS 200A. History of Time flowed out at a constant rate and was used to tell time, but it also wasn’t very accurate. In 1092, a Chinese monk Keeping track of time dates as far back as the Ice Age. named Su Sung created a water clock very similar to Over 20,000 years ago hunters scratched lines and made mechanical clocks known today. This water clock was five holes in sticks and bones. Scientists believe that they were stories tall and had a very large water wheel. possibly counting the days between the phases of the moon. The first known mechanical clock invented was in the 13th century very similar to the water clock but used mercury and it controlled the drum at a more constant rate. Galileo Galilei was the first to study the pendulum and Christiaan Huygens used his work to create the first clock using a pendulum. Over time they found that the longer the pendulum, the more accurate the time, so that is why pendulum clocks are a tall rectangular shape. Jost Burgi invented the minute hand in 1577 for an astronomer. In the Many civilizations over the years have developed ways to early 18th century a telecommunications engineer, Warren keep track of time but one thing remained the same no Marrison, developed a very large, highly accurate clock matter the location or the century. Time was tracked as based on the regular vibrations of a quartz crystal in an equal and constant increments, thus the creation of clocks. electrical circuit, created the first quartz clock. Clocks also evolved over time starting with obelisks and the use of complicated water clocks to the atomic clock With the creation of clocks, the problem arose where currently used today. every city around the world was on their own time, basing noon on when the sun passed over the town. To correct this problem, Great Britain was the first country to standardize time. Greenwich Mean Time (GMT) was the solution. England’s Royal Greenwich Observatory located on the zero-degree longitude meridian, became the center of the first time zone and leading the way to the concept of time zones. In 1884, delegates from 25 countries attended The International Meridian Conference in Washington D.C. Obelisks were used in ancient Egypt to tell time and as a where they established time zones one hour apart, result they found the longest and shortest days. The referencing solar time (high noon is when the sun reaches meridian line was also discovered, a line joining north and the center meridian of that time zone). south by observing the shortest shadow cast by the obelisk that would always point in the same direction regardless of The National Institute of Standards and Technology the season. Sundials were created using the obelisk theory, (NIST) in the U.S. built the first atomic clock in 1949. but it was found that these smaller obelisk versions were These clocks are the most accurate time and frequency not as accurate and hard to read. standards known and is based off of atomic physics. The system of Coordinated Universal Time (UTC) came into use on January 1, 1972. UTC replaced the term GMT but the time remains the same, it differs from your local time by a specific number of hours. The number of hours depends on the number of time zones between your location and the location of the zero meridian (which passes through Greenwich, England). When local time changes from Daylight Saving to Standard Time, or vice versa, UTC does not change. However, the difference between UTC and local time does change-by 1 hour. UTC is a 24-hour clock system. The hours are numbered beginning with 00 hours at midnight through 12 hours at noon to 23 hours and 59 minutes just before the next Sundials only worked on sunny days, so the water clock midnight. See “The American Practical Navigator” was created. A container was filled with water and it (Bowditch) (Pub. 9) for a full description of UTC. 2 - 3 RADIO TIME SIGNALS 200B. Time Zones The military uses the phonetic alphabet for time zones; therefore each time zone also has a letter associated with it. Today the world is split up into 25 time zones. The The term Zulu is “Z” which is UTC time. system is centered on zero-degrees longitude in Greenwich, England (See sec. 200A, para 6). The graphic Some countries observe Daylight Savings Time (DST). below shows the amount of hours that each area is offset Each country has its own start/stop days and times. from UTC. In the US we have names for our time zones, starting from See graphic below for a map of US time zones. the east to west they are: The US starts daylight savings time at 2am local time on Eastern Standard Time (EST) the 2nd Sunday in March and clocks are changed ahead Central Standard Time (CST) one hour. At 2am on the 1st Sunday in November is Mountain Standard Time (MST) when clocks are moved back one hour. Pacific Standard Time (PST) Arizona, Puerto Rico, Hawaii, US Virgin Islands and Alaskan Standard Time (AKST) American Samoa do not observe Daylight Savings Time. Hawaii-Aleutian Standard Time (HST) During daylight savings time, the US Time Zones go from “Standard” to “Daylight”, for example Eastern Daylight Time (EDT). 2 - 4 RADIO TIME SIGNALS 200C. The National Institute of Standards and example by lengthening, doubling, splitting or tone Technology (NIST)-in general modulation of normal seconds markers. Example: The NIST has two radio stations broadcasting time and frequency information 24-7 for the United States; stations WWV and WWVH. They broadcast time announcements, standard time intervals, standard frequencies, UT1 time corrections (Astronomical time for Universal Time), a BCD (Binary-coded Decimal) time code, geophysical alerts, marine storm warnings, and Global Positioning System (GPS) status reports. They operate in the high frequency (HF) portion of the radio spectrum. Each station radiates 10,000 W on 5, 10, and 15 MHz; and 2500 W on 2.5 and 20 MHz. Each frequency is broadcast from a separate transmitter and carries the same information to ensure one frequency is usable at all times. 200C.1 Time Announcements 200C.6 Geophysical Alerts Voice announcements are made from WWV and The National Oceanic and Atmospheric Administration WWVH once every minute. The announced time is (NOAA) broadcasts geophysical alert messages that “Coordinated Universal Time” (UTC). provide information about solar terrestrial conditions and are updated at 0000, 0300, 0600, 0900, 1200, 200C.2 Standard Time Intervals 1500, 1800, 2100 UTC. The pulses mark the seconds of each minute, except for the 29th and 59th second pulses which are omitted To obtain alerts: completely. *By phone: (1) 303 497 3235 200C.3 Standard Frequencies *Radio station broadcasts: WWV & WWVH The 440 Hz tone, also known as A440 (A4) is the *Space Weather Prediction Center Website: international standard for musical pitch, musical note A http://www.swpc.noaa.gov above middle C. The NIST started broadcasting this A440 *Tips on viewing the Aurora: from WWV in 1936. In 1939 it served as the audio http://www.swpc.noaa.gov/Aurora frequency reference for calibration of musical instruments. The 440 Hz tone can be heard on WWV and WWVH Definitions: stations and is omitted from the first hour of the UTC day. *A [A#] & K indices are measurements of the behavior of the magnetic field in and around the Earth. K 200C.4 UT1 Time Corrections ranges from 0-9. A ranges from 0-400. K-index is UT1 is the Astronomical time for Universal Time (UT). broadcast at [K TIME] 0000, 0300, 0600, 0900, 1200, Coordinated Universal Time (UTC) is the mean solar time 1500, 1800, 2100 UTC. at zero-degree longitude. UTC time is based on atomic *Geomagnetic storms are disturbances in the clocks which are more stable than the Earth’s rotational geomagnetic field caused by gusts in the solar wind rate. The International Earth Rotation and Reference that blows by Earth. Systems Service (IERS), measures Earth’s rotation and *Radio blackouts are disturbances of the ionosphere publishes the difference between UT1 and UTC. The caused by X-ray emissions from the Sun. actual correction is known as a leap second. A leap second *Space weather describes the conditions in space that is the second (most corrections are tenths of a second) affect Earth and its technological systems. Includes all added to UTC in order to keep it synchronized with observed geomagnetic storms, solar radiation storms astronomical time. (proton events) and radio blackouts. 200C.5 BCD Time Code *Solar flux [#] is a measurement of the intensity of solar Binary-coded Decimal (BCD) time code is computer radio emissions with a wavelength of 10.7cm (a time. NIST broadcasts this code on a 100 Hz subcarrier frequency of about 2800 Mhz). Range varies from 50 given in a serial fashion at a rate of one pulse per second. to 300. The information carried by the time code includes the *Solar radiation storms are elevated levels of radiation current minute, hour, and day of year and may be used with that occur when the numbers of energetic particles the same accuracy as the audio time frequencies. The increase. appropriate seconds markers may be emphasized, for 2 - 5 RADIO TIME SIGNALS K indices Geomagnetic Solar Radiation Storm Level Radio Blackout Level Space Weather [K#] Storms [S level] [R level] [space level] K = 9 G5 S5 R5 Extreme K = 8 G4 S4 R4 Severe K = 7 G3 S3 R3 Strong K = 6 G2 S2 R2 Moderate K = 5 G1 S1 R1 Minor Message Format: Sections Basic Intro Solar-terrestrial indices for [DATE] follow.
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