NTP - Using an Atomic Clock Receiver for Time Synchronisation

Atomic clocks are the most accurate timekeeping devices developed by man. Modern atomic clocks are so accurate that even in 100 million years less than a second of time would be lost.

This accuracy makes them ideal references for a NTP server (Network Time Protocol). NTP is a protocol widely used to synchronize computer networks across the Internet of local Area Network (LANs).

This article explains how to synchronise a computer network using NTP to an atomic clock source.

Atomic clocks are so accurate that a universal timescale has been developed called UTC (Coordinated Universal Time) that is based on the time told by atomic clocks. UTC is globally used and is the same everywhere enabling different computer networks to be synchronized to the same time.

Unfortunately atomic clocks are hugely expensive, extremely delicate and quite bulky pieces of equipment, so they are only really to be found in large scale physical laboratories or in highly technical pieces of equipment such as satellites.

Fortunately a dedicated NTP server can synchronize to UTC time using an atomic clock as a reference source by either making us of the national time and frequency transmissions or the GPS (Global Positioning System) network.

Many national physics laboratories such as NPL in the UK, NPL in Germany and NIST in the USA, broadcast a UTC time reference on long wave radio transmission. These signals can be picked up by a NTP server using a radio receiver. Unfortunately the radio transmissions are not broadcast by every country and the signals are finite.

Fortunately the constellation of satellites that make up the USA’s GPS network all have an onboard atomic clock. This signal is used by satellite navigation receivers to work out location but can equally be used by a GPS NTP server as a timing source.

Using either a radio referenced NTP server or GPS time server, synchronization to within a few milliseconds of UTC is possible.