NTP servers are the easiest, most accurate and secure method of receiving a UTC time source (Coordinated Universal Time). Most dedicated NTP time servers will run in the background automatically synchronising the devices on a network completely automatically.
However, there are some common problems that occasionally occur in using a network time server but fortunately most can be solved relatively easily.
Losing A GPS time signal
GPS is one of the most efficient sources of UTC time. The GPS signal is available literally anywhere on the planet where there is a clear view of the sky. At any one time there are at least three satellites within range of any location and unlike radio referenced transmissions there are no maintenance outages so the signal is always uninterrupted.
However, some people find that they keep losing their GPS signal when using a GPS NTP time server. Very rarely this can be caused by extra terrestrial occurrences (solar flares – not little green men), however more commonly signal loss occurs when there has been insufficient time give for the initial acquisition lock.
To ensure a continuous signal make sure you follow manufacturer’s recommendation for obtaining acquisition. This usually means leaving the GPS time server to get a good lock for at least 24 hours (so all satellites have been in view). If not enough time is given to this then it is possible the GPS time server will lose a satellite and therefore timing information.
One second delay in a radio clock compared to internet or GPS
This is a very frequent occurrence when using a radio time server using signals such as the MSF transmission broadcast by the UK’s National Physical Laboratory. This occurs normally after the insertion of a Leap Second. Leap seconds are introduced once or twice a year to compensate for the slowing of the Earth’s rotation and to keep UTC in line with the Greenwich Meridian.
While NTP will automatically account for leap seconds with signals like the MSF it can often take some time as there is no Leap Second announcement. This announcement normally allows NTP to prepare for the leap second (which normally occurs in the last second of the last day in June or December). As signals such as MSF do not announce the upcoming leap second it can take some time for it to be accounted for. In some cases it can take a few days in others minutes. A simple solution is to manually announce the leap second.
However, if this is not done, NTP will eventually discover the leap second and adjust the network clocks.