Article From SubmitYOURArticle: Installing a Radio Referenced NTP Server

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Title: Installing a Radio Referenced NTP Server
Word Count: 707
Author: David Evans
Category: Computers & Internet
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David Evans
http://www.timetools.co.uk

Installing a Radio Referenced NTP Server
Many networks in organisations suffer from a lack of time
synchronisation between servers, workstations and other
network components. This can lead to problems processing
time critical information and transactions. However, a
solution has been available for many years in the form of
NTP, the Network Time Protocol. NTP can be used to
synchronise network time clients to an accurate time
reference, or NTP server. A stratum 1 NTP server
synchronises to a precise external timing reference such as
GPS or radio time & frequency transmissions and provides a
precise timing resource to a local area network.

There are a number of accurate external timing references
available, the most well known being GPS. However, many
countries also provide a radio time and frequency reference
that can be used for time synchronisation. In the UK, the
MSF radio time signal is broadcast from Anthorn, Cumbria,
at a frequency of 60 KHz. The German DCF-77 radio time
transmissions are broadcast from Frankfurt at 77.5 KHz. The
US WWVB radio time reference is transmitted from Boulder,
Colorado, at 60 KHz. There are also a number of other
countries that provide similar time references. Most
broadcasts operate on different frequencies and encode data
differently and thus require different tuned antennas and
decoding firmware.

Radio time broadcasts have a finite range and are generally
restricted to the national boundaries where the broadcast
emanates. GPS timing references can operate anywhere in the
world. However, the advantage of radio is that generally,
a good signal can be obtained indoors close the host NTP
time server, whereas a GPS antenna requires a good view of
the sky. This can significantly reduce installation costs
and simplify NTP server implementation.

A radio based NTP server generally consists of a
rack-mountable time server, and a separate radio antenna.
The radio antenna is used to receive the radio time and
frequency broadcast. The antenna should be located in an
area where a good consistent signal can be received.

There are a number of factors that can affect radio time
signal reception. If the radio antenna is sited underground
or in a basement, signal reception may be significantly
impaired. If the antenna is located inside a metal
structure or enclosure, again this may also impact signal
reception. Also, if the antenna is sited too close to
'electrically noisy' equipment, such as PC monitors, can
affect reception. However, usually, provided the antenna is
at least 1m from a PC monitor, reception will not be
affected.

Most radio time and frequency receivers consist of a
ferrite, or bar, antenna contained within a plastic
enclosure. The ferrite antenna generally runs the length of
the antenna enclosure. Ferrite antennas are unidirectional
antennas that have an ideal orientation. The ferrite
antenna should be mounted in a horizontal plane at right
angles to the source of the time code transmission. For
example, if the source of the transmission is north of the
antenna location, the antenna ferrite should be mounted
horizontally pointing East-West, at right angle to North.
In this orientation, the ferrite has the largest area
perpendicular to the transmission. If the antenna is
rotated, as the angle to the source of transmission
reduces, so the sensitivity of the antenna is reduced. Most
radio time and frequency transmissions continually
broadcast precise time and date information. Data is
generally encoded into a series of 60 pulses, one pulse per
second. Each pulse represents a data-bit that makes up the
current time and date over a period of 1 minute. When a
minutes worth, or 60 pulses, have been received, the NTP
server can attempt signal decoding. In this manner a time
stamp should be received by the time server once each
minute. If the signal drops out, or is incorrectly
received, then the resulting decode will fail. Good
continuous signal reception is required to provide a
reliable time reference.

To summarise, a NTP server can provide an organisation with
a precise timing reference for synchronising computers and
network infrastructure. Time synchronisation between
workstation and servers is an important aspect of data and
transaction processing in most operating systems. A radio
based NTP server is an ideal solution that can be easily
installed and implemented to provide a solution to computer
network time synchronisation issues.

----------------------------------------------------
This article was written by Dave Evans, a computer network
design engineer that specialises in computer time and
frequency systems. Dave has a number of years experience
using NTP with GPS and radio time references. If you would
like more information on NTP server systems, please visit:
http://www.timetools.co.uk/ntp-servers/ntp-server-s5000.htm