Twenty years ago it would have been unlikely for a private individual to have an atomic clock at home. With few exceptions, precise time technology was used exclusively by professionals at national scientific laboratories, the military, and a small number of specialized commercial companies. But in the past ten years an abundance of military, dot-com, and telecom surplus has made it possible for motivated individuals to obtain yesterday’s start-of-the-art timing technology for personal use today. High-end precise timekeeping instruments, such as atomic frequency standards and frequency counters,
VLF receivers and phase comparators, Loran-C and GPS disciplined oscillators can be hunted and purchased for cents on the dollar. Today hundreds of individuals own rubidium, cesium, or GPS-based frequency standards and are keeping time at home to fractions of a microsecond. Many of these people are ham radio operators who have a
technical appreciation of, and need for, precise frequency. Some are retired military personnel who are nostalgic for gear they used years ago in the service. A few are curious engineers who enjoy the challenge of building clocks with ever increasing accuracy. Others are clock and watch collectors who want to augment their mechanical collections with specimens of modern electronic timekeepers. Whatever the circumstances precise timekeeping is a historically rich, intellectually stimulating, and
technically challenging field. Amateur time enthusiasts join mailing lists such as time-nuts or TACGPS. The latter was started by Dr. Tom Clark about ten years ago to freely share his clever, low-cost, PC software controlled, Motorola VP GPS receiver-based precise timing solution. In short, some of us have caught the “time bug” and are on the slippery slope of ever greater frequency stability and more precise time.
The following sections are a view into my clock collection, time & frequency experiments, and home timing laboratory.
ATOMIC CLOCK COLLECTION
People collect just about anything: books, stuffed animals, postage stamps, cars, vacuum tubes, clocks and watches. Some of us have a hobby of collecting modern and vintage electronic instruments related to precise time: oscillators, atomic frequency standards, phase comparators, time code displays, and radio (WWV, WWVB, Loran-C) or satellite time/frequency receivers (GOES, GPS). Over the years my collection has grown to include instruments from companies such as Austron, Astrodata, Berkeley, Bliley, Datum, Efratom, FEI, Fluke, FTS, General Radio, Hewlett-Packard/Agilent,
Kinemetrics, Odetics, Oscilloquartz, Sigma Tau, Stanford Research, Spectracom, Sulzer, Symmetricom, Systron-Donner, Tracor, Trak, True Time, TST, and Vectron. Photos of the collection may be found on my web site. There are frequency standards ranging from a vintage 1 kc General Radio tuning fork oscillator to a modern 100 MHz Sigma Tau hydrogen maser, representing stabilities from 10-3 to 10-15.
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