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Minilock ← 6910
Programmable Precision Measurement Receiver
Minilock 6910 was a digital programmable precision
measurement receiver,
developed and built by Schlumberger in München
(Germany) around 1990, as the successor to the
Minilock 6900.
The receiver covers all
frequencies between 10 kHz and 1890 MHz and supports all common
modes (modulation types),
including AM, FM, PM, USB and LSB with a variety of bandwidths.
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The receiver was commonly used by a number of agencies around the world,
for interception and fingerprinting of suspicious radio signals
and for frequency spectrum monitoring,
for example in Germany, The Netherlands, and South Korea.
The basic 6910 system consists of two units:
a smaller unit that contains the power supply and
the control panel,
and a larger 'black box' that contains
the actual receiver parts.
Optionally, the set could be completed with a
6901 Panoramic Display
and a 4940 Antenna Multiplexer.
The units are linked together via cables at the back.
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Between the RF Unit and the Control unit, three coaxial cables, a power
cable and a data cable are needed. For this reason, the two units can not
be separated more than approx. 20 cm. The optional 6901 Panoramic Display,
that could also be used with the Minilock 6900, is connected via three
coaxial cables that can have any length.
The optional 4940 Antenna Multiplexer
can only be used if the (optional) 6906 Control Adapter is present at the
rear of the 6910 RF Unit.
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The block diagram shows how the various parts of the Minilock 6910
are connected together. At the top left is the antenna input, that
is passed via a switchable attenuator to a pre-selection filter
and then to a low-noise low-distortion pre-amplifier. From there
is is mixed with the first Local Oscillator signal (LO), passed
through the 1st IF-stage and then mixed with the 2nd LO, resulting
in a 10.7 MHz signal. At the right are the IF and the various
(demodulated) outputs.
At the bottom right is the Audio Frequency amplifier (AF) and the
speaker output. The local oscillators, the attentuator, the pre-selection
filters and the various IF stages, are all controlled by the CPU,
depending on the current frequency band. The CPU has various interfaces
to the outside world and for connecting accessories,
such as the 4940 Antenna Multiplexer or an XY plotter.
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The Minilock 6910 consist of two major building blocks: the RF Unit and
the Control Unit. The two units are connected by means of a series of cables
at the rear. All controls are on the Control Unit that was usually mounted
on a desk. If space was limited, the RF Unit was often mounted below the desk.
The distance between the two unit is, of course, limited by the supplied cables.
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The control panel is a separate unit that is usually mounted at the front
size of the Control Unit, as shown in the image on the right. In that case,
the Control Unit is placed on the desk. To the right of the control panel
are two power buttons: a red one and a black one.
If space is limited, the control panel can also be
detached from the
Control Unit, allowing both (large) units to be mounted below the desk,
whilst the control panel was within reach of the operator. The extenstion
cable allows the control panel to be placed approx. one meter away.
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The red power button is used to turn the entire system ON or OFF.
After switching the Minilock 6910 ON, maximum stability is obtained
after 20 minutes. The black power button can be used to put the system
in STANDBY mode. In this mode, the entire receiver is powered down,
except for the internal 10 MHz reference oscillator. As a result,
the receiver will have its optimum stability when waking up from
STANDBY mode. The power buttons are part of the Control Unit and can
not be removed with the control panel. They should stay within reach
of the operator.
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The RF Unit is the larger of the two units. It measures
444 x 236 x 490 cm, weights 19 kg and fits a standard 19" rack.
It contains all HF, IF and AF components and is controlled
by the 6902 Control Unit. The antenne is be connected to
the N-connector at the rear. All frequency and band dependent parts
and filters inside the RF Unit are controlled by an 6800 microprocessor.
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The 6910 RF Unit is usually placed on top of the 6910 Control
Unit, so that the control panel is easily accessible when the
reciever is placed on a table. It is also possible however,
to place the RF Unit under the Control Unit. Furthermore,
the Control Panel can be detached (see above).
In order to obtain maximum precision and accuracy, the receiver
uses its own built-in temperature stabilized 10 MHz reference
oscillator. A few minutes after turning the receiver on, the
stability of the reference oscillator is good enough for general use.
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Maximum stability however, is obtained after several hours.
For this reason, the receiver can be put in STAND BY when
unused, by means of the ST BY switch.
This leaves the reference oscillator powered.
The Control Unit is locked to the same 10 MHz
reference signal via a coax cable at the back. If an even better
precision and stability is required, the internal reference
oscillator can be locked to an external 10 MHz source, e.g.
from a Rubidium, DCF or GPS Standard.
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In order to get a real-time view of the frequency spectrum around
the currently received frequency, the optional 6901 Panoramic Display
can be used. The Display Unit, that could also be used with the
earlier Minilock 6900, is housed in a 19" case that
can be stacked with the other units. Alternatively, the Panoramic Display
can be mounted elsewhere in a desk.
It connects to the RF unit by means of three coaxial cables.
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The Antenna Multiplexer allows size different antennas to be connected to
the Minilock 6910. Only one of these antennas will be connected to the
receiver at any time, controlled via a 25-way interface at the rear.
The 4940 Multiplexer can only be used if the 6906 Control Adapter is
installed at the rear of the 6910 RF Unit.
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The Minilock 6910 can be programmed to automatically select the appropriate
antenna for any given frequency band. In addition, the 4940 has extra switched
outputs that can be used for a variety of functions, such as selecting an
amplifier or attentuator.
The 4940 Multiplexer if fully controlled by the Minilock 6910, but can
also be operated manually, using a series of
push-buttons at the front panel.
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Frequency 10 kHz - 1.89 GHz (in 10 Hz steps) Impedance 50 Ω Preselection Automatic, 19 ranges Attenuator 0, 3, 10, 20, 30, 40, 50, 60 dB Pre-amplifier (selectable) 15 ± 1 dB Stability 10-7 after 20 minutes at 25°C Drift 2·10-9/°C Bandwidth 1-100kHz in 0.5kHz steps
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Intermediate Frequency (IF)
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829.3 MHz (0.01-520 MHz) 229.3 MHz (520-1010 MHz) 250.7 MHz (1010-1370 MHz) 950.7 MHz (1370-1890 MHz)
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© Crypto Museum. Last changed: Monday, 30 May 2022 - 15:42 CET.
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