Introduction to Time and Frequency

Introduction

This section is for those interested in the measurement of precise time, and the generation and measurement of frequency with high precision. Of particular interest to Radio Amateurs and Amateur Astronomers, these two fundamental properties are closely linked, since of course time (measured in seconds) is the inverse (reciprocal) of frequency, measured in events per second, or Hz.

The international unit of time, the second, is defined as the time interval equal to 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cęsium-133 atom. The international unit of frequency, the Hertz, is defined as the frequency of periodic events occuring at one second intervals.

There are many interesting resources for those interested in Time and Frequency. Among the best are:

A Walk through Time (NIST, USA)

Brooke Clarke N6GCE

Brooks Shera's GPS-Controlled Frequency Standard

METAS (Swizerland)

National Measurements Laboratory (Australia)

National Physical Laboratory Time Metrology (UK)

NIST Time and Frequency Division (USA)

Physikalisch-Technische Bundesanstalt (Germany)

Reference Clock Serial Timecode Formats

Time and Frequency Standard Station Information

Time and Frequency Standards Services (New Zealand)

U.S. Naval Observatory Time Service Department

The JAVA Internet Time Clock to the right is courtesy of Bennet. If you don't see the clock, it will be because you don't have the JAVA run-time module installed on your computer.

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