NIST recommended practice guide : WWVB radio controlled clocks : recommended practices for manufacturers and consumers

2009·3.9 MB·English

guide
NATL INST OF STAND & TECH e
NIST
PUBLICATIONS
lObQb^
A11107
WWVB
Radio
Controlled Clocks:
Recommended
Practices
Manufacturers
for
and Consumers
(2009 Edition)
Michael A. Lombardi, Andrew N. Novick,
John P. Lowe, Matthew J. Deutch,
Glenn K. Nelson, Douglas S. Sutton,
William C. Yates, and D. Wayne Hanson
Special
Publication
0-14
wmm
mmm

NIST Recommended Practice Guide
Special Publication 960-14
WWVB
Radio
Controlled Clocks:
Recommended
Practices
Manufacturers
for
and Consumers
(2009 Edition)
Michael A. Lombardi, Andrew N. Novick,
John P. Lowe, Matthew J. Deutch,
Glenn K. Nelson, Douglas S. Sutton,
and William C. Yates
NIST Physics Laboratory
D. Wayne Hanson
Time Signal Engineering
August 2009
U.S. Department ofCommerce
Gary Locke, Secretary
National Institute ofStandards and Technology
Patrick D. Gallagher, Deputy Director
Certain commercial entities, equipment, or materials may be identified in
this document in orderto describe an experimental procedure or concept
adequately. Such identification is not intended to imply recommendation or
endorsement by the National Institute ofStandards andTechnology, nor is it
intended to imply that the entities, materials, or equipment are necessarily the
best available forthe purpose.
National Institute ofStandards andTechnology
Special Publication 960-14
Natl. Inst. Stand. Technol.
Spec. Publ. 960-14
64 pages (August 2009)
CODEN: NSPUE2
U.S. GOVERNMENT PRINTING OFFICE
WASHINGTON: 2009
For sale by the Superintendent ofDocuments
U.S. Government Printing Office
Internet: bookstore.gpo.gov Phone: [phone] Fax: [phone]
Mail: Stop SSOP, Washington, DC 20402-0001
Foreword
FOREWORD
Radio controlled clocks represent a true revolution in timekeeping.
WWVB
Clocks that synchronize to NIST radio station now number in
the millions in the United States, and new sales records are being established
every year. As a result, many ofus are now accustomed to having clocks
in our homes, offices, and on ourwrists that always display the correct
time and that neverrequire adjustment. This NISTRecommended
Practice Guide was written to provide guidance to both manufacturers
and consumers ofradio controlled clocks. Throughvoluntary compliance
with the recommended practices listed here, manufacturers can benefit
by continuing to develop more reliable and usable radio controlled products,
increasing both consumer confidence and sales. Consumers can benefit
by using this guide to help them select and purchase radio controlled
clock products, to learn how the products work, and to help troubleshoot
reception problems.
iii

Acknowledgments
This booklet is a revised version ofthe original booklet published in January
2005. Although not a majorrevision, it updates information about radio station
WWVB
and the United States daylight saving time rules that were changed
in 2007. It also makes a few small corrections to the time zone tables and
maps. In addition, the recommended practices forradio controlled clock
manufacturers have been revised slightly to incorporate new information
collected by the authors since the original booklet was published.
The authors gratefully acknowledge those who reviewedthis document and
made numerous helpful suggestions including: Michael Chiu and Hans-
Joachim Sailer ofC-MaxTechnology; Etsuro Nakajima andAihara Fumikazu
ofthe Casio Corporation; Glenn Burdett ofthe Spectracom Corporation; Rod
Mack ofUltralink; John Rowland and Gene Fornario, the founder and co-
moderatorrespectively ofthe Casio Waveceptor forum onYahoo.com; Tom
O'Brian, Chiefofthe NISTTime and Frequency Division; and David Smith,
Chairman ofthe Editorial Review Board at NIST's Boulder laboratories. We
also thank all those who have called and e-mailed NIST in recent years and
shared theirpersonal experiences with radio controlled clock (RCC) products.
Their questions and comments inspired us to create this guide.
v

1
Table of Contents
Table of Contents
List ofFigures x
List ofTables xi
1. Introduction 1
WWVB
2. Technical Description of 3
3. Recommended Practices for ClockAccuracy,
Clock Display, and Controls 5
3.A. Analog Clock Displays 5
3.B. Digital Clock Displays 6
RCC
3.C. Controls 7
3.D. Compatibility with Other Stations 7
3.E. Signal Quality Indicator 8
3.F. Antenna Orientation 9
4. Recommended Practices for Clock Synchronization 11
4.A. Initial SynchronizationWhen Clock
Is FirstTurned On or Reset 1
4.A.1. Analog Clocks (HandAlignment) 11
4.A.2. Digital Clocks 11
4.B. Synchronization by Radio atAssignedTimes 11
4.B.1. Amount ofTimeAllotted to a
SynchronizationAttempt 14
4.B.2. Status ofDisplay During a
SynchronizationAttempt 14
vii
61
WWVB
Radio Controlled Clocks
4.C. Synchronization by Radio at a
Time Selected by the User 14
4.D. Manual Clock Synchronization 14
4.E. Synchronization Indicator 15
4.E.I. Digital Clock Synchronization Indicator 16
4.E.2. Analog Clock Synchronization Indicator
1
4.F. Adjustment ofDisplay to Compensate
for Delays Introduced During Synchronization 17
5. Recommended Practices for
Time Zone Settings 19
5.A. Time Zone Selection 19
6. Recommended Practices for
Daylight SavingTime (DST) 27
6.A. Handling ofTransition Days 27
6.B. Disabling/Enabling DST Switch 28
6.C. DST Indicator 28
7. Recommended Practices for Leap Seconds,
LeapYears, and the Two-DigitYear Code 29
7.A. Handling ofLeap Seconds 29
7.B. Handling ofLeapYears 29
7.C. Handling ofTwo-DigitYear Code 30
8. Recommended Practices for
Hardware Specifications 31
8.A. Receiver Specifications 3
iii