DOCSLIB.ORG

Time and Frequency Users Manual

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

A 11 10 3 07512T o NBS SPECIAL PUBLICATION 559 J U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards Time and Frequency Users' Manual NATIONAL BUREAU OF STANDARDS The National Bureau of Standards' was established by an act of Congress on March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is per- formed by the National Measurement Laboratory, the National Engineering Laboratory, and the Institute for Computer Sciences and Technology THE NATIONAL MEASUREMENT LABORATORY provides the national system of physical and chemical and materials measurement; coordinates the system with measurement systems of other nations and furnishes essential services leading to accurate and uniform physical and chemical measurement throughout the Nation's scientific community, industry, and commerce; conducts materials research leading to improved methods of measurement, standards, and data on the properties of materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government agencies; develops, produces, and distributes Standard Reference Materials; and provides calibration services. The Laboratory consists of the following centers: Absolute Physical Quantities 2 — Radiation Research — Thermodynamics and Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical ser- vices to the public and private sectors to address national needs and to solve national problems; conducts research in engineering and applied science in support of these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities; provides engineering measurement traceability services; develops test methods and proposes engineering standards and code changes; develops and proposes new engineering practices; and develops and improves mechanisms to transfer results of its research to the ultimate user. The Laboratory consists of the following centers: Applied Mathematics — Electronics and Electrical Engineering 2 — Mechanical Engineering and Process Technology 2 — Building Technology — Fire Research — Consumer Product Technology — Field Methods. THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal agencies; and provides the technical foundation for computer-related policies of the Federal Government. The Institute consists of the following centers: Programming Science and Technology — Computer Systems Engineering. 'Headquarters and Laboratories at Gaithersburg, MD, unless otherwise noted; mailing address Washington, DC 20234. : Some divisions within the center are located at Boulder, CO 80303. Banroai mravm v. — JAN 1 8 1980 r\crt ftcc -£Lt/ Time and Frequency Users' Manual r\0- 5^ Edited by: George Kamas Sandra L. Howe Time and Frequency Division National Measurement Laboratory National Bureau of Standards Boulder, Colorado 80303 U.S. DEPARTMENT OF COMMERCE Luther H. Hodges, Jr., Under Secretary Jordan J. Baruch, Assistant Secretary for Science and Technology NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director Issued November 1979 Library of Congress Catalog Card Number: 79-600169 National Bureau of Standards Special Publication 559 Nat. Bur. Stand. (U.S.), Spec. Pubi. 559, 256 pages (Nov. 1979) CODEN. XNBSAV (Supersedes NBS Technical Note 695, May 1977) U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1979 For sale by the Superintendent of Documents, U.S. Government Printing Office. Washington, D.C. 20402 Stock No. 003-003-02137-1 - Price $6. (Add 2u percent additional for other than U.S. mailing). CONTENTS PAGE CHAPTER 1. INTRODUCTION: WHAT THIS BOOK IS ABOUT 1.1 WHO NEEDS TIME & FREQUENCY? 1 1.2 WHAT ARE TIME AND FREQUENCY ? 4 1.3 WHAT IS A STANDARD ? . 5 1.3.1 CAN TIME REALLY BE A STANDARD? 6 1.3.2 THE NBS STANDARDS OF TIME AND FREQUENCY 6 1.4 HOW TIME AND FREQUENCY STANDARDS ARE DISTRIBUTED 7 1.5 THE NBS ROLE IN INSURING ACCURATE TIME AND FREQUENCY 7 • 1.6 WHEN DOES A MEASUREMENT BECOME A CALIBRATION ? . .8 1.7 TERMS USED . 8 1.7.1 MEGA, MILLI, PARTS PER... AND PERCENTS ...... 8 1.7.2 FREQUENCY 10 1.8 DISTRIBUTING TIME AND FREQUENCY SIGNALS VIA CABLES AND TELEPHONE LINES . .11 1.9 TIME CODES 13 CHAPTER 2. THE EVOLUTION OF TIMEKEEPING 2.1 TIME SCALES 17 2.1.1 SOLAR TIME 17 2.1.2 ATOMIC TIME 18 A. Coordinated Universal Time ......... 19 B. The New UTC System 19 2.1.3 TIME ZONES 20 2.2 USES OF TIME SCALES 21 2.2.1 SYSTEMS SYNCHRONIZATION 21 2.2.2 NAVIGATION AND ASTRONOMY 22 2.3 INTERNATIONAL COORDINATION OF TIME AND FREQUENCY ACTIVITIES 23 2.3.1 THE ROLE OF THE INTERNATIONAL TIME BUREAU (BIH) 23 2.3.2 THE ROLE OF THE NATIONAL BUREAU OF STANDARDS (NBS) 23 2.3.3 THE ROLE OF THE U.S. NAVAL OBSERVATORY (USNO) AND THE DOD PTTI PROGRAM . 24 CHAPTER 3. THE ALGEBRA AND CONVENTIONS FOR TIME AND FREQUENCY MEASUREMENTS 3.1 EXPRESSING FREQUENCY DIFFERENCE (IN HERTZ, kHz, MHz , ETC.) 28 3.2 RELATIVE (FRACTIONAL) FREQUENCY, F (DIMENSIONLESS) 28 3.3 RELATIVE (FRACTIONAL) FREQUENCY DIFFERENCE, S (DIMENSIONLESS) . .28 3.4 EXAMPLE OF ALGEBRA AND SIGN CONVENTIONS IN TIME AND FREQUENCY MEASUREMENTS . 29 3.4.1 Television Frequency Transfer Measurements (covered in Chapter 7) .29 3.4.2 Television Line-10 Time Transfer Measurements (covered in Chapter 8) . 29 iii PAGE 3.5 USING TIME TO GET FREQUENCY 30 3.6 A MATHEMATICAL DERIVATION 31 3.7 DEFINITIONS 32 CHAPTER 4. USING TIME AND FREQUENCY IN THE LABORATORY 4.1 ELECTRONIC COUNTERS . .33 4.1.1 SOURCES OF COUNTER ERROR 34 4.1.2 FREQUENCY MEASUREMENTS 34 A. Direct Measurement . .35 B. Prescaling 35 C. Heterodyne Converters .......... 35 D. Transfer Oscillators .......... 37 4.1.3 PERIOD MEASUREMENTS 39 4.1.4 TIME INTERVAL MEASUREMENTS 40 4.1.5 PHASE MEASUREMENTS 42 4.1.6 PULSE-WIDTH DETERMINATION MEASUREMENTS 43 4.1.7 COUNTER ACCURACY 43 A. Time Base Error ... .43 B. Gate Error . 44 C. Trigger Errors . , .45 4.1.8 PRINTOUT AND RECORDING 48 4.2 OSCILLOSCOPE METHODS 48 4.2.1 CALIBRATING THE OSCILLOSCOPE TIME BASE ....... 49 4.2.2 DIRECT MEASUREMENT OF FREQUENCY 50 4.2.3 FREQUENCY COMPARISONS 50 A. Lissajous Patterns 50 B. Sweep Frequency Calibration: An Alternative Method . .55 4.2.4 TIME INTERVAL MEASUREMENTS 56 4.3 WAVEMETERS 56 4.4 HETERODYNE FREQUENCY METERS 57 4.5 DIRECT-READING ANALOG FREQUENCY METERS 58 4.5.1 ELECTRONIC AUDIO FREQUENCY METER 58 4.5.2 RADIO FREQUENCY METER 59 4.6 FREQUENCY COMPARATORS 60 4.7 AUXILIARY EQUIPMENT 60 4.7.1 FREQUENCY SYNTHESIZERS 60 4.7.2 PHASE ERROR MULTIPLIERS 61 4.7.3 PHASE DETECTORS 62 4.7.4 FREQUENCY DIVIDERS 63 A. Analog or Regenerative Dividers ........ 63 B. Digital Dividers ........... 63 4.7.5 ADJUSTABLE RATE DIVIDERS 64 4.7.6 SIGNAL AVERAGERS 65 iv PAGE 4.8 PHASE LOCK TECHNIQUES 66 4.9 SUMMARY '.67 CHAPTER 5. THE USE OF HIGH-FREQUENCY RADIO BROADCASTS FOR TIME AND FREQUE NCY CALIBRATIONS 5.1 BROADCAST FORMATS 69 5.1.1 WWV/WWVH 69 5.1.2 CHU 70 5.1.3 ATA 71 5.1.4 IAM 72 5.1.5 IBF 72 5.1.6 JJY 72 5.1.7 OMA . .74 5.1.8 VNG 74 A. Time Signals 74 B. Time Code 74 C. Announcements ............ 74 D. DUT1 Code 75 E. Accuracy ............. 75 F. Frequency and Time Generating Equipment ...... 75 5.1.9 ZUO 75 A. Carrier Frequencies and Times of Transmission . .76 B. Standard Time Intervals and Time Signals ...... 76 C. Standard Audio Frequencies ......... 76 D. Accuracy 76 E. DUT1 Code 76 5.2 RECEIVER SELECTION 81 5.3 CHOICE OF ANTENNAS AND SIGNAL CHARACTERISTICS 82 5.4 USE OF HF BROADCASTS FOR TIME CALIBRATIONS 86 5.4.1 TIME-OF-DAY ANNOUNCEMENTS 86 5.4.2 USING THE SECONDS TICKS 86 A. Receiver Time Delay Measurements ....... 86 B. Time Delay Over the Radio Path 87 C. Using an Adjustable Clock to Trigger the Oscilloscope . .88 D. Delayed Triggering: An Alternate Method that Doesn't Change the Clock Output 90 E. Using Oscilloscope Photography for Greater Measurement Accuracy . 92 5.4.3 USING THE WWV/WWVH TIME CODE 92 A. Code Format . 93 B. Recovering the Code . .94 5.5 USE OF HF BROADCASTS FOR FREQUENCY CALIBRATIONS 96 5.5.1 BEAT FREQUENCY METHOD 97 5.5.2 OSCILLOSCOPE LISSAJOUS PATTERN METHOD 98 5.5.3 OSCILLOSCOPE PATTERN DRIFT METHOD 100 5.5.4 FREQUENCY CALIBRATIONS BY TIME COMPARISON OF CLOCKS 100 v PAGE 5.6 FINDING THE PROPAGATION PATH DELAY 101 5.6.1 GREAT CIRCLE DISTANCE CALCULATIONS 101 ' 5.6.2 PROPAGATION DELAYS . 102 5.7 THE NBS TELEPHONE TIME-OF-DAY SERVICE 105 5.8 SUMMARY. 105 CHAPTER 6. CALIBRATIONS USING LF AND VLF RADIO TRANSMISSIONS 6.1 ANTENNAS FOR USE AT VLF-LF 107 6.2 SIGNAL FORMATS 107 6.3 PROPAGATION CHARACTERISTICS AND OTHER PHASE CHANGES 108 6.4 FIELD STRENGTHS OF VLF-LF STATIONS Ill 6.5 INTERFERENCE .113 6.6 USING WWVB FOR FREQUENCY CALIBRATIONS 113 6.6.1 PHASE-SHIFT IDENTIFICATION 114 6.6.2 METHODS OF FREQUENCY COMPARISON 115 6.7 USING OTHER LF AND VLF STATIONS FOR TIME AND FREQUENCY CALIBRATIONS .
Recommended publications
  • August 2002 7:45 PM THURSDAY 8Th August 2002 Greenhills Community House NERG Inc

    August 2002 7:45 PM THURSDAY 8Th August 2002 Greenhills Community House NERG Inc

    NERG NEWS Incorporated 1985 in Victoria Reg No A0006776V - http://nerg.asn.au August 2002 7:45 PM THURSDAY 8th August 2002 Greenhills Community House NERG Inc. At the meeting this month: PO Box 270 Greensborough • Annual General Meeting Victoria 3088 • Inside a Panel Antenna What’s on this month? This month there will be loads to see and do. For a starters it’s August so it’s time for the AGM and the election of office bearers! - That should only take up the first few minutes of the meeting so don’t be late or you’ll get elected to something . Get your agenda items and nominations in quickly. • Birthday Celebrations Next a talk by a well-known club member on the inside secrets of a high gain "panel" • Membership fees are due antenna for mobile phone towers. Later the NERG Birthday Party finishes off Membership Fees Due Now International Lighthouse & the night with the traditional Chocolate Cake A quick reminder to all NERG members that st Lightship Weekend and other goodies. 2002 fees are due from the 1 August. Fees This event runs from 10 am (local EST) are $30 single, $40 family, $20 concession, th th Finally, a reminder that memberships fees Saturday 17 to 10 am Monday 19 August, rising much less than inflation! overlapping the Australian RD contest. are due and Marg will happily accept all Send payment to our treasurer (address on contributions to keep the club going another back of NERG NEWS) or drop in to our next NERGs plans will be discussed at the year.
  • Standard Frequencies and Time Signals from NBS Stations WWV and WWVH

    Standard Frequencies and Time Signals from NBS Stations WWV and WWVH

    UNITED STATES DEPARTMENT OF COMMERCE Frederick H. Mueller, Secretary NATIONAL BUREAU OF STANDARDS A. V. Astin, Director Standard Frequencies and Time Signals From NBS Stations WWV and WWVH National Bureau of Standards Miscellaneous Publication 236 Reprinted July 1, 1961 with corrections (First issued December 1, 1960) Detailed descriptions are given of six technical services broadcast by National Bureau of Standards radio stations WWV and WWVH. The services include 1, standard radio frequencies; 2, standard audio frequencies; 3, standard time intervals; 4, standard musical pitch; 5, time signals; and 6, radio propagation forecasts. Other domestic and foreign standard frequency and time signal broadcasts are tabulated. 1. Technical Services and Related Information The National Bureau of Standards’ radio sta- at 1900 UT (Universal Time, UT, is the same as tions WWV (in operation since 1923) and WWVH GMT and GCT). (since 1948) broadcast six widely used technical (b) Accuracy services: 1, Standard radio fiequencies; 2, stand- Since December 1, 1957, the standard radio ard audio frequencies ; 3, standard time intervals ; transmissions from stations WWV and WWVII 4, standard musical pitch; 5, time signals; 6, radio have been held as nearly constant as possible with propagation forecasts. respect to the atomic frequency standards which The radio stations are located as follows: WWV, constitute the United States Frequency Standard Beltsville, Maryland (Box 182, Route 2, Lanham, (USFS), maintained and operated by the Radio Marvland) : WWVH. Maui. Hawaii (Box 901. Standards Laboratory of the National Bureau of PunGene, Maui). Coordinatk of the stitions are.:‘ Standards. Carefully made atomic standards WWV (lat. 38’59’33’’ N, long.
  • 1 Diocese of Harrisburg Geography of Pennsylvania

    1 Diocese of Harrisburg Geography of Pennsylvania

    7/2006 DIOCESE OF HARRISBURG GEOGRAPHY OF PENNSYLVANIA Red Italics – Reference to Diocesan History Outcome: The student knows and understands the geography of Pennsylvania. Assessment: The student will apply the geographic themes of location, place and region to Pennsylvania today. Skills/Objectives Suggested Teaching/Learning Strategies Suggested Assessment Strategies The student will be able to: 1a. Using student desk maps, locate and highlight the 1a. On a blank map of the U.S., outline the state of state, trace rivers and their tributaries and circle Pennsylvania, label the capital, hometown and two 1. Locate and identify the state of Pennsylvania, its major cities. largest cities. capital, major cities and his hometown. On a blank map of the U.S. outline the state of 1b. Using the globe, determine the latitude and longitude Pennsylvania; within the state of Pennsylvania, outline of the state. the Diocese of Harrisburg. Label the city where the cathedral is located. 1c. Using a Pennsylvania highway map, design a road tour visiting major Pennsylvania cities. 1b. Using the desk map, identify the latitude line closest Using a Pennsylvania highway map with the counties to the hometown and two other towns of the same within the Diocese of Harrisburg marked, do the parallel of latitude. Identify the longitude nearest the following: first, in each county, identify a city or town state capital and two other towns on the same with a Catholic church; then design a road tour visiting meridian of longitude. each of these cities or towns. Using a desk map, place marks on the most-western, the most-northern, and the most-eastern tips of the Diocese 1d.
  • QUICK REFERENCE GUIDE Latitude, Longitude and Associated Metadata

    QUICK REFERENCE GUIDE Latitude, Longitude and Associated Metadata

    QUICK REFERENCE GUIDE Latitude, Longitude and Associated Metadata The Property Profile Form (PPF) requests the property name, address, city, state and zip. From these address fields, ACRES interfaces with Google Maps and extracts the latitude and longitude (lat/long) for the property location. ACRES sets the remaining property geographic information to default values. The data (known collectively as “metadata”) are required by EPA Data Standards. Should an ACRES user need to be update the metadata, the Edit Fields link on the PPF provides the ability to change the information. Before the metadata were populated by ACRES, the data were entered manually. There may still be the need to do so, for example some properties do not have a specific street address (e.g. a rural property located on a state highway) or an ACRES user may have an exact lat/long that is to be used. This Quick Reference Guide covers how to find latitude and longitude, define the metadata, fill out the associated fields in a Property Work Package, and convert latitude and longitude to decimal degree format. This explains how the metadata were determined prior to September 2011 (when the Google Maps interface was added to ACRES). Definitions Below are definitions of the six data elements for latitude and longitude data that are collected in a Property Work Package. The definitions below are based on text from the EPA Data Standard. Latitude: Is the measure of the angular distance on a meridian north or south of the equator. Latitudinal lines run horizontal around the earth in parallel concentric lines from the equator to each of the poles.
  • Reception of Low Frequency Time Signals

    Reception of Low Frequency Time Signals

    Reprinted from I-This reDort show: the Dossibilitks of clock svnchronization using time signals I 9 transmitted at low frequencies. The study was madr by obsirvins pulses Vol. 6, NO. 9, pp 13-21 emitted by HBC (75 kHr) in Switxerland and by WWVB (60 kHr) in tha United States. (September 1968), The results show that the low frequencies are preferable to the very low frequencies. Measurementi show that by carefully selecting a point on the decay curve of the pulse it is possible at distances from 100 to 1000 kilo- meters to obtain time measurements with an accuracy of +40 microseconds. A comparison of the theoretical and experimental reiulb permib the study of propagation conditions and, further, shows the drsirability of transmitting I seconds pulses with fixed envelope shape. RECEPTION OF LOW FREQUENCY TIME SIGNALS DAVID H. ANDREWS P. E., Electronics Consultant* C. CHASLAIN, J. DePRlNS University of Brussels, Brussels, Belgium 1. INTRODUCTION parisons of atomic clocks, it does not suffice for clock For several years the phases of VLF and LF carriers synchronization (epoch setting). Presently, the most of standard frequency transmitters have been monitored accurate technique requires carrying portable atomic to compare atomic clock~.~,*,3 clocks between the laboratories to be synchronized. No matter what the accuracies of the various clocks may be, The 24-hour phase stability is excellent and allows periodic synchronization must be provided. Actually frequency calibrations to be made with an accuracy ap- the observed frequency deviation of 3 x 1o-l2 between proaching 1 x 10-11. It is well known that over a 24- cesium controlled oscillators amounts to a timing error hour period diurnal effects occur due to propagation of about 100T microseconds, where T, given in years, variations.
  • VCO) for Frequency Shifting Or Synthesis in RF Front-End Circuitry

    VCO) for Frequency Shifting Or Synthesis in RF Front-End Circuitry

    A Low Power, Low Noise, 1.8GHz Voltage-Controlled Oscillator by Donald A. Hitko Bachelor of Science in Electrical Engineering GMI Engineering & Management Institute, 1994 Submitted to the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering and Computer Science at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY February 1997 © 1997 Massachusetts Institute of Technology All rights reserved. A u th o r ......... ......................................................................................... Department of Electrical Engineering and Computer Science September 27, 1996 C ertified by ........... ............ ...................................................... Charles G. Sodini Professor of Electrical Engineering and Computer Science fl q Thesis Supervisor Accepted by ..................-----. - ............. Acceptedby F. R. Morgenthaler Chai n, Department \'minittee on Graduate Students • ~MAR 0 6 1997 UF•BARIES A Low Power, Low Noise, 1.8 GHz Voltage-Controlled Oscillator by Donald A. Hitko Submitted to the Department of Electrical Engineering and Computer Science on September 27, 1996, in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering. Abstract Transceivers which form the core of many wireless communications products often require a low noise voltage-controlled oscillator (VCO) for frequency shifting or synthesis in RF front-end circuitry. Since many wireless applications are focused on portability, low power operation is a necessity. Techniques for implementing oscillators are explored and then evaluated for the purposes of simultaneously realizing low noise and low power operation. Models for the design of oscillators and the analysis of oscillation stability are covered, and methods of calculating phase noise are discussed. These models and theories all point to the need for a high quality, passive, integrated inductor to meet the system goals.
  • Primer > PCR Measurements

    Primer > PCR Measurements

    PCR Measurements PCR Measurements 1,E-01 1,E-02 1,E-03 1,E-04 1,E-05 1,E-06 1,E-07 1,E-08 1,E-09 10-5 10-4 10-3 0,01 0,1 1 10 100 Drift limiting region Jitter limiting region PCR Measurements Primer New measurements in ETR 2901 Synchronizing the Components of a Video Signal Abstract Delivering TV pictures from studio to home entails sending various types of One of the problems for any type of synchronization procedure is the jitter data: brightness, sound, information about the picture geometry, color, etc. on the incoming signal that is the source for the synchronization process. and the synchronization data. Television signals are subject to this general problem, and since the In analog TV systems, there is a complex mixture of horizontal, vertical, analog and digital forms of the TV signal differ, the problems due to jitter interlace and color subcarrier reference synchronization signals. All this manifest themselves in different ways. synchronization information is mixed together with the corresponding With the arrival of MPEG compression and the possibility of having several blanking information, the active picture content, tele-text information, test different TV programs sharing the same Transport Stream (TS), a mechanism signals, etc. to produce the programs seen on a TV set. was developed to synchronize receivers to the selected program. This The digital format used in studios, generally based on the standard ITU-R procedure consists of sending numerical samples of the original clock BT.601 and ITU-R BT.656, does not need a color subcarrier reference frequency.
  • TX517EVM Users Manual . (Rev. B)

    TX517EVM Users Manual . (Rev. B)

    TX517 Dual Channel, 17-Level With RTZ, Integrated Ultrasound Transmitter User's Guide Literature Number: SLOU317B August 2011–Revised December 2011 2 SLOU317B–August 2011–Revised December 2011 Submit Documentation Feedback Copyright © 2011, Texas Instruments Incorporated Contents 1 Default Configuration .......................................................................................................... 9 2 Buttons ............................................................................................................................ 10 3 SYNC Trigger .................................................................................................................... 11 4 Power up TX517 ................................................................................................................ 12 5 Power Supplies for Output Waveform .................................................................................. 13 5.1 Input/Output Pattern ................................................................................................... 14 6 Board Configuration .......................................................................................................... 20 7 EVM Schematics ............................................................................................................... 21 8 Bill of Materials ................................................................................................................. 28 9 PCB Layouts ....................................................................................................................
  • A Stability Analysis of Divergence Damping on a Latitude–Longitude Grid

    A Stability Analysis of Divergence Damping on a Latitude–Longitude Grid

    2976 MONTHLY WEATHER REVIEW VOLUME 139 A Stability Analysis of Divergence Damping on a Latitude–Longitude Grid JARED P. WHITEHEAD Department of Mathematics, University of Michigan, Ann Arbor, Ann Arbor, Michigan CHRISTIANE JABLONOWSKI AND RICHARD B. ROOD Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Ann Arbor, Michigan PETER H. LAURITZEN Climate and Global Dynamics Division, National Center for Atmospheric Research,* Boulder, Colorado (Manuscript received 24 August 2010, in final form 25 March 2011) ABSTRACT The dynamical core of an atmospheric general circulation model is engineered to satisfy a delicate balance between numerical stability, computational cost, and an accurate representation of the equations of motion. It generally contains either explicitly added or inherent numerical diffusion mechanisms to control the buildup of energy or enstrophy at the smallest scales. The diffusion fosters computational stability and is sometimes also viewed as a substitute for unresolved subgrid-scale processes. A particular form of explicitly added diffusion is horizontal divergence damping. In this paper a von Neumann stability analysis of horizontal divergence damping on a latitude–longitude grid is performed. Stability restrictions are derived for the damping coefficients of both second- and fourth- order divergence damping. The accuracy of the theoretical analysis is verified through the use of idealized dynamical core test cases that include the simulation of gravity waves and a baroclinic wave. The tests are applied to the finite-volume dynamical core of NCAR’s Community Atmosphere Model version 5 (CAM5). Investigation of the amplification factor for the divergence damping mechanisms explains how small-scale meridional waves found in a baroclinic wave test case are not eliminated by the damping.
  • 8 Alert Input Monitor

    8 Alert Input Monitor

    Chapter 1: Introduction OMEGAPHONE® OMA-P1108 Voice Synthesized Monitoring & Alarm System User’s Manual IMPORTANT SAFETY INSTRUCTIONS Your OMA-P1108 has been carefully designed to give you years of safe, reliable performance. As with all electrical equipment, however, there are a few basic precautions you should take to avoid hurting yourself or damaging the unit: • Read the installation and operating instructions in this manual carefully. Be sure to save it for future reference. • Read and follow all warning and instruction labels on the product itself. •To protect the OMA-P1108 from overheating, make sure all openings on the unit are not blocked. Do not place on or near a heat source, such as a radiator or heat register. • Do not use your OMA-P1108 near water, or spill liquid of any kind into it. • Be certain that your power source matches the rating listed on the AC power transformer. If you’re not sure of the type of power supply to your facility, consult your dealer or local power company. • Do not allow anything to rest on the power cord. Do not locate this product where the cord will be abused by persons walking on it. • Do not overload wall outlets and extension cords, as this can result in the risk of fire or electric shock. •Never push objects of any kind into this product through ventilation holes as they may touch dangerous voltage points or short out parts that could result in a risk of fire or electric shock. •To reduce the risk of electric shock, do not disassemble this product, but return it to Omega Customer Service, or other approved repair facility, when any service or repair work is required.
  • Five Years of VLF Worldwide Comparison of Atomic Frequency Standards

    Five Years of VLF Worldwide Comparison of Atomic Frequency Standards

    RADIO SCIENCE, Vol. 2 (New Series), No. 6, June 1967 Five Years of VLF Worldwide Comparison of Atomic Frequency Standards B. E. Blair,' E. 1. Crow,2 and A. H. Morgan (Received January 19, 1967) The VLF radio broadcasts of GBR(16.0 kHz), NBA(18.0 or 24.0 kHz), and NSS(21.4 kHz) have enabled worldwide comparisons of atomic frequency standards to parts in 1O'O when received over varied paths and at distances up to 9000 or more kilometers. This paper summarizes a statistical analysis of such comparison data from laboratories in England, France, Switzerland, Sweden, Russia, Japan, Canada, and the United States during the 5-year period 1961-1965. The basic data are dif- ferences in 24-hr average frequencies between the local atomic standard and the received VLF radio signal expressed as parts in 10"'. The analysis of the more recent data finds the receiving laboratory standard deviations, &, and the transmission standard deviation, ?, to be a few parts in 10". Averag- ing frequencies over an increasing number of days has the effect of reducing iUi and ? to some extent. The variation of the & with propagation distance is studied. The VLF-LF long-term mean differences between standards are compared with the recent portable clock tests, and they agree to parts in IO". 1. Introduction points via satellites (Steele, Markowitz, and Lidback, 1964; Markowitz, Lidback, Uyeda, and Muramatsu, Six years ago in London, the XIIIth General Assem- 1966); improvements in the transmission of VLF and bly of URSI adopted a resolution (No. 2) which strongly LF radio signals (Milton, Fey, and Morgan, 1962; recommended continuous very-low-frequency (VLF) Barnes, Andrews, and Allan, 1965; Bonanomi, 1966; and low-frequency (LF) transmission monitoring US.
  • High Frequency (HF)

    High Frequency (HF)

    Calhoun: The NPS Institutional Archive Theses and Dissertations Thesis Collection 1990-06 High Frequency (HF) radio signal amplitude characteristics, HF receiver site performance criteria, and expanding the dynamic range of HF digital new energy receivers by strong signal elimination Lott, Gus K., Jr. Monterey, California: Naval Postgraduate School http://hdl.handle.net/10945/34806 NPS62-90-006 NAVAL POSTGRADUATE SCHOOL Monterey, ,California DISSERTATION HIGH FREQUENCY (HF) RADIO SIGNAL AMPLITUDE CHARACTERISTICS, HF RECEIVER SITE PERFORMANCE CRITERIA, and EXPANDING THE DYNAMIC RANGE OF HF DIGITAL NEW ENERGY RECEIVERS BY STRONG SIGNAL ELIMINATION by Gus K. lott, Jr. June 1990 Dissertation Supervisor: Stephen Jauregui !)1!tmlmtmOlt tlMm!rJ to tJ.s. eave"ilIE'il Jlcg6iielw olil, 10 piolecl ailicallecl",olog't dU'ie 18S8. Btl,s, refttteste fer litis dOCdiii6i,1 i'lust be ,ele"ed to Sapeihil6iiddiil, 80de «Me, "aial Postg;aduulG Sclleel, MOli'CIG" S,e, 98918 &988 SF 8o'iUiid'ids" PM::; 'zt6lI44,Spawd"d t4aoal \\'&u 'al a a,Sloi,1S eai"i,al'~. 'Nsslal.;gtePl. Be 29S&B &198 .isthe 9aleMBe leclu,sicaf ,.,FO'iciaKe" 6alite., ea,.idiO'. Statio", AlexB •• d.is, VA. !!!eN 8'4!. ,;M.41148 'fl'is dUcO,.Mill W'ilai.,s aliilical data wlrose expo,l is idst,icted by tli6 Arlil! Eurse" SSPItial "at FRIis ee, 1:I.9.e. gec. ii'S1 sl. seq.) 01 tlls Exr;01l ftle!lIi"isllatioli Act 0' 19i'9, as 1tI'I'I0"e!ee!, "Filill ell, W.S.€'I ,0,,,,, 1i!4Q1, III: IIlIiI. 'o'iolatioils of ltrese expo,lla;;s ale subject to 960616 an.iudl pSiiaities.