User's Manual

The 400A series clocks will, when connected to an appropriate 484 series radio receiver and programmed for
radio time code synchronisation, automatically synchronise to the radio time code information transmitted
from radio station DCF located at Mainflingen near Frankfurt or from MSF at Rugby. The clock may display
BST - program function 3, selection 9 - (MSF synchronised), CET - program function 3, selection 11 - (DCF
synchronised) or UTC (GMT) from either MSF - selection 10 - or DCF - selection 12. The DCF signal is
transmitted at 77.5KHz and is derived from an atomic clock at the Physics Institute of Brunswick. The MSF
signal is transmitted at 60KHz and is referenced to the Caesium Beam Oscillator at the National Physical
Laboratory.
The type 484.02 (MSF) and 484.03 (DCF) time signal receivers are housed in a compact weather-proof case
and are connected to the clock or master clock by a single cable pair. In many locations the receiver will
operate within the building. In difficult reception areas, where an external mounting point is required, the
receiver unit may be located up to 200 metres from the clock.
The type 484.06 (MSF) and 484.07 (DCF) time signal receivers are low cost units for internal use only.
Installation
The 484 series radio time code receiver should be mounted:
• At least 2 metres from the 400A series clock.
• At the greatest practical distance from:
Other electrical equipment including computers, fluorescent lights and signs, metal girders and
reinforced concrete walls. Any other sources of electrical noise.
• Preferably on the outside of the building (484.02 and 484.03 only) as high as possible. The case is
weatherproof to IP65 but it is preferable to provide some protection from direct rain.
• With the cable entry on the lower face of the case (484.02 and 484.03).
The 484 series receiver may be connected to the 400A series clock directly by means of the cable provided or,
at a greater distance, by means of a suitable extension cable.
At distances of up to 10 metres unscreened two core cable may be used. At greater distances, or in areas of
high electrical noise, a two core screened cable must be used with the screen grounded at one end only. The
maximum recommended distance between the receiver and master clock is 200 metres.
Alignment
The 484.02 and 484.03 radio receivers have dual ferrite antenna which normally permit location regardless of
orientation to the transmitter. The receiver is mounted by means of the four fixing holes in the rear surface
which are accessed after removing the front cover. The four mounting holes are located outside of the central
sealed compartment. The 484.06 and 484.07 receivers have a single antenna element and are supplied with
an adjustable mounting bracket to enable orientation with the longest face of the receiver at 90° to the
direction of the transmitter.
The front cover of the 484.02 and 484.03 receivers may be removed to enable an indicator LED to be viewed.
The indicator LED for the 484.06 and 484.07 receiver is located in the front face of the unit. The alignment of
the receiver is correct when the LED flashes on/off once per second.
Signal Reception
Under normal circumstances the DCF signal provides reliable operation at distances of up to 1500km. MSF
signals are normally usable up to 1000km. Greater operating ranges are possible at night. The received and
decoded signal provides an operating accuracy of better than
+
/
-
20ms and provides completely automatic
seasonal time changes.
In best conditions the 400A series clock will take three minutes to synchronise with the transmitted time code
from either DCF or MSF. When the 400A series clock is `locked’ to the transmitted signal, the colon between
the hours and minutes characters is illuminated continuously. During periods of signal failure or signal
corruption the clock will maintain timekeeping using its internal high stability quartz crystal oscillator and the
colons will flash on/off every second.
It should be noted that MSF is off the air for maintenance purposes from 10:00 to 14:00 on the first Tuesday
of each month and usually for up to two weeks during the summer months for annual maintenance. The MSF
transmission status can be checked by telephoning 020 8943 6493.
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Radio Time Code Synchronisation
Issue 2.2