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Search Publications by: Michael A. Lombardi (Assoc)

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Displaying 51 - 75 of 141

A common-view disciplined oscillator

May 24, 2010
Author(s)
Michael A. Lombardi, Aaron P. Dahlen
This paper describes a common-view disciplined oscillator (CVDO) that locks to a reference time scale through the use of common-view Global Positioning System (GPS) satellite measurements. A Proportional-Integral-Derivative (PID) controller obtains near

How Accurate is a Radio Controlled Clock?

March 1, 2010
Author(s)
Michael A. Lombardi
This paper discusses the factors that determine the accuracy of radio controlled clocks. The topics covered including the accuracy of the time signal station, path delay, synchronization errors, and the time error that accumulates between synchronizations.

Distributing UTC(NIST) to Industrial Time and Frequency Users

November 18, 2009
Author(s)
Michael A. Lombardi, Victor S. Zhang
The National Institute of Standards and Technology (NIST) maintains one of the world s most accurate and stable time scales, UTC(NIST), as well as the NIST-F1 cesium fountain, the primary frequency standard for the United States. These standards are

WWVB Radio Controlled Clocks: Recommended Practices for Manufacturers and Consumers (2009 edition)

September 8, 2009
Author(s)
Michael A. Lombardi, Andrew N. Novick, John P. Lowe, Matthew J. Deutch, Glenn K. Nelson, Douglas D. Sutton, William C. Yates, D. W. Hanson
Radio controlled clocks represent a true revolution in timekeeping. Clocks that synchronize to NIST radio station WWVB now number in the millions in the United States, and new sales records are being established every year. As a result, many of us are now

Time and Frequency Users Manual

September 2, 2009
Author(s)
Michael A. Lombardi
This book is for the person who needs information about making time and frequency measurements. It is written at a level that will satisfy those with a casual interest as well as laboratory engineers and technicians who use time and frequency every day. It

Establishment of the SIM Time Scale

August 1, 2009
Author(s)
J. Mauricio Lopez-Romero, N. Munoz, Michael A. Lombardi
The SIM time and frequency metrology working group has developed a comparison network for the Americas, with the goals of improving metrology in the SIM region and to allow as many countries as possible to participate in the network. As of May 2008, ten

The SIM Time Network and its Contributions to Metrology in the Americas

April 1, 2009
Author(s)
Michael A. Lombardi
The SIM Time Network (SIMTN) has been one of the great success stories of the Sistema Interamericano de Metrologia (SIM), a regional metrology organization (RMO) that includes the 34 member nations of the Organization of American States (OAS). The SIMTN

Stopwatch and Timer Calibrations (2009 edition)

January 28, 2009
Author(s)
Jeff C. Gust, Robert M. Graham, Michael A. Lombardi
Stopwatch and timer calibrations are perhaps the most common calibrations performed in the field of time and frequency metrology. Hundreds of United States laboratories calibrate many thousands of timing devices annually to meet legal and organizational

PTTI Capabilities of the Modernized LORAN System

December 1, 2008
Author(s)
Kirk Montgomery, Michael A. Lombardi
This paper covers the current status and future plans of the modernized LORAN systems in North America, the European Union, Asia, & Saudi Arabia. Special focus is placed on the enhanced LORAN system in North America and Europe. These modernized systems

The SIM Time and Frequency Network

December 1, 2008
Author(s)
Michael A. Lombardi, Andrew N. Novick, Jose M. Lopez, Francisco Jimenez, Jean-Simon Boulanger, Raymond Pelletier, Ricardo de Carvalho, Raul Solis, Carlos Donado, Harold Sanchez, Carlos A. Quevedo, Gregory Pascoe, Daniel Perez
The Sistema Interamericano de Metrologia (SIM) consists of national metrology institutes (NMIs) located in the 34 member nations of the Organization of American States (OAS), which extends throughout North, Central, and South America, and the Caribbean

Time and Frequency Transfer Activities at NIST

December 1, 2008
Author(s)
Victor S. Zhang, Michael A. Lombardi
The National Institute of Standards and Technology (NIST) maintains one of the world s most accurate and stable time scales, and also developed and maintains the primary frequency standard for the United States. Various techniques are used to compare the

Establishment of the SIM Time Scale

October 22, 2008
Author(s)
Michael A. Lombardi, Nelida Diaz-Munoz, J. Mauricio Lopez-Romero
The SIM time and frequency metrology working group has developed a comparison network for the Americas, with the goals of improving metrology in the SIM region by allowing as many countries as possible to participate in the network. As of May 2008, 10

The SIM Network: Improved Time Coordination for North, Central, and South America

April 23, 2008
Author(s)
Jose M. Lopez, Michael A. Lombardi, Andrew Novick, Jean-Simon Boulanger, R. de Carvalho, R. Solis, Francisco Jimenez
The Sistema Interamericano de Metrologia (SIM) consists of national metrology institutes (NMIs) located in the 34 member nations of the Organization of American States (OAS), which extends throughout North, Central, and South America, and the Caribbean

Selecting a Primary Frequency Standard for a Calibration Laboratory

April 1, 2008
Author(s)
Michael A. Lombardi
Calibration laboratories can choose from a variety of frequency standards, including quartz oscillators, atomic oscillators, and oscillators disciplined to agree with reference signals from the Global Positioning System (GPS) satellites or other sources

The Accuracy and Stability of Quartz Watches

February 1, 2008
Author(s)
Michael A. Lombardi
A short review article about quartz wristwatches that presents measurements of their accuracy and stability. Measurements of both the stepping motors and crystal oscillators inside four quartz watches are made over a 30-day interval, and the results are

NIST Primary Frequency Standards and the Realization of the SI Second

December 1, 2007
Author(s)
Michael A. Lombardi, Thomas P. Heavner, Steven R. Jefferts
As the base unit of time interval, the second holds a place of preeminence in the world of metrology. Time interval, and its reciprocal, frequency, can be measured with more resolution and less uncertainty than any other physical quantities. The precise

Effects of the Rooftop Environment on GPS Time Transfer

December 5, 2006
Author(s)
Michael A. Lombardi, Andrew N. Novick
We examine the effects of the rooftop environment on GPS time transfer, in particular the effects of multipath reflections from nearby metallic objects. Three different antennas sites were selected on the roof of the NIST laboratories at Boulder, Colorado