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Technical Information
Operating Instructions
FM614
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Impressum
Meinberg Funkuhren GmbH & Co. KG
Auf der Landwehr 22
D-31812 Bad Pyrmont
Internet: http://www.meinberg.de
Email: info@meinberg.de
Telefon: ++49 (0) 52 81 / 9309-0
Telefax: ++49 (0) 52 81 / 9309-30
March, 06th, 2006
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Table of contents
Impressum ............................................................................................ 2
General Information about DCF77 ...................................................... 4
General information about position of antenna ................................... 5
Features of FM614 ............................................................................... 5
Front panel layout ................................................................................ 6
Handling of FM614 .............................................................................. 6
Technical specification FM614 ............................................................ 7
CE Label ..................................................................................... 7
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General Information about DCF77
Like radio remote clocks the field strength meter FM614 receives the signal from the
long wave transmitter DCF77. This long wave transmitter installed in Mainflingen
near Frankfurt/Germany transmits the reference time of the Federal Republic of
Germany. This time reference is either the Central European Time (Mitteleuropäische
Zeit, MEZ) or the Central European Summer Time (Mitteleuropäische Sommerzeit,
MESZ). The transmitter is controlled by the atomic clock plant at the Federal Physical
Technical Institute (PTB) in Braunschweig/Germany and transmits the current time of
day, date of month and day of week in coded second pulses. Once every minute the
complete time information is available.
At the beginning of every second the amplitude of the high precision 77.5 kHz
carrier frequency is lowered by 75% for a period of 0.1 or 0.2 sec. The length of these
time marks represent a binary coding scheme using the short time mark for logical
zeroes and the long time mark for logical ones. The information on the current date
and time as well as some parity and status bits can be decoded from the time marks of
the 15th up to the 58th second every minute. The absence of any time mark at the 59th
second of a minute signals that a new minute will begin with the next time mark.
Our radio remote clocks decode the highly accurate information on date and time
within a wide range around Germany. So some of our clocks are installed in Bilbao/
Spain as well as in the city of Umeå in northern Sweden - fully satisfying the
requirements of the users. The radio remote clocks automatically switch to summertime and back. The reception of the time information is free of charge and does not need
to be registered.
Generally it is important to position the antenna in an optimal way. It should be
mounted at least 30 centimeters away from the clock unit and from solid steel. The
antenna should be aligned at a right angle to the direction of the transmitter (Frankfurt).
Figure: Decoding Scheme
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General information about position of antenna
The antenna of DCF-receivers includes a ferrite rod which must be aligned to the
transmitter. For best receiption the longitudinal side of the antenna must point to
Frankfurt. The antenna should be installed with a distance of at least 30cm to all metal
objects because they would detune the antenna resonance. A distance of several meters
to computer monitors must be kept. If they are running in a high screen resolution
mode, their line frequency is close to the carrier frequency of the DCF-transmitter,
which would cause a worse or no reception.
Features of FM614
The FM614 has been developed to help service technicians in finding the best
possible position for installing a DCF antenna or receiver module.
It includes two synchronous demodulators for the DCF-signal. One signal path
detects the field strength of the 77.5 kHz-signal at the output of the antenna, the
second receiver circuit demodulates the timing marks. The determined signal level is
indicated by an analog display, the timing marks are made visible by a LED and can be
observed acoustic by a piezo buzzer.
The FM614 is designed for both AC-line and accu supply. During AC-supply the
internal accus are charged. This state is signalled by a LED, overcharging is not
possible. If the FM614 often runs in accu supply mode, the accumulators should be
discharged (unplugg power supply cable and switch into accu supply mode) at times to
avoid the loss of capacity. The status of capacity can be checked with the help of the
analog display.
The scope of supply includes an active ferrite antenna AI01, a AC-power cord and a
coaxial antenna cable (RG174).
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Front panel layout
level[dBm]
0
0
1
-
-
6
0
0
-
5
7
-
accu
0
-
4
0
-
3
0
o
k
0
8
-
0
9
-
d
a
o
l
Acc. check
Mod.
Charge
field strength meter
FM614
Accu on
Piezo
AC- lin e
off
Handling of FM614
a) Mode of operation
Use switch "Accu / AC-line" to choose one of the modes accu or AC-supply.
b) Charging
The accumulators are charged whenever the FM614 is plugged to the ACpower-supply. LED "Charge" indicates this status.
c) Checking the capacity
By pressing key "Acc. check" the status of capacity is indicated by the analog
display. With the help of the marking it is possible to recognize if the accus have
to be charged. The antenna shouldn't be connected to carry out this test.
d) Measurement of field strength
The antenna AI01 has to be connected to the input of FM614 by using the
coaxial cable to perform this test. By varying the position of the antenna or the
alignment to the transmitter, the maximum of field strength can be found.
Besides a high field strength the flashing of the LED "Mod." exactly in rythm of
the timing marks is important. This marks can be observed acoustic by a piezo
buzzer.
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If the FM614 isn't in use for a longer period, it should be stored with
switch position "AC-Line" to avoid deep-discharging of the internal
accus.
Technical specification FM614
Indicating range: output level of antenna: -100 dbm to -30 dbm
Measuring
precision: 5%
AC power supply: 230V/0.5W
Internal
power supply: 5.0V
Operating time: approximately 8 hours with charged accus
Temperature
range: 0 ... 50oC
Case: Plastic sloped case Elegant of company Bobla
Dimensions: 200mm x 112mm x 64mm
Connectors: Power cord receptacle for mains supply
SMB-connector for antenna cable
Scope of supply: FM614 in sloped case, AC-power cord
active antenna AI01, antenna cable RG174 (3m)
CE Label
This device conforms to the directive 89/336/EWG on the approximation of the laws of the Member States of the European Community relating to electromagnetc compatibility.
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