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DF-5 Sequitor
Radio Beacon Tracker

DF-5 is a mobile radio direction finder (RDF), based on the correlative interferometer principle, introduced around 1993 by Datong in Leeds (UK). The device was intended as a beacon tracker and was sold exclusively to governments and law enforcement agencies. It was used by various European organisations, including the UK's GCHQ and the Dutch Police, for following suspected vehicles, very important persons (VIPs), money transports, etc. It is the successor of the DF-4.

The device is housed in a metal enclosure that measures 365 x 333 x 107 mm and weights 3000 grams. All connections are at the front panel. The controls and the readout of bearing and signal strength are on an external display.

The complete system was supplied in a large unobtrusive leather executive style briefcase, such as the ones that are used by airline pilots. It has pockets at the sides, and offers room for the display unit, additional interfaces, operating instructions, cables and (optionally) the CMD-3 telecommander for remote controlling a beacon.
  
Datong DF-5 direction finder

The device can track any beacon between 25 and 500 MHz, 1 but in most European countries the use of law enforcement beacons was commonly restricted to the 2 and 8 metre bands at the time. The DF-5 is a four-channel interferometer, which uses a minimum of three and a maximum of four external (covert) antennas, one of which can be assigned as a high-gain reference antenna.

The DF-5 has an external handheld remote control unit, that shows the bearing (rose) and the relative signal strength of the RF signal from the beacon. It supports beacons with continuous as well as pulsed transmission. It uses digital signal processing to suppress multi-path propagation and to obtain an accurate and reliable bearing to a (moving) beacon. When used in combination with an intelligent beacon, such as the Datong D-903, the status of the vehicle under surveillance (stationary or moving) will be visible on the display unit. It has a built-in electronic gyro­scope — allowing it to be used in a moving vehicle — and offers support for a moving map display.

A number of unique features of the DF-5 are described by David A. Tong in US Patent 4,809,012. The price of the bare DF-5 receiver was the equivalent of EUR 28,000 to EUR 32,000 in 1993, depending on the quantity [2]. The device featured here was manufactured in late 1994 and was updated at least once in June 1996. In The Netherlands it was used until at least the early 2000s.

  1. Extendable upwards to 1500 MHz and down to Medium Frequency (MF).

Leather carrying case
Datong DF-5 direction finder
Datong DF-5 direction finder
Frontal view
Front panel
DF-5 with gyroscope fitted at the rear
Remote control unit (DFC-1)
A
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A
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Leather carrying case
A
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Datong DF-5 direction finder
A
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Datong DF-5 direction finder
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Frontal view
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Front panel
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DF-5 with gyroscope fitted at the rear
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Remote control unit (DFC-1)

Features
All connections of the DF-5 are at the front panel, as shown in the diagram below. The device has no controls, but relies on the DFC-1 remote control unit (the display) that should be connected to CTRL1 socket at the top right. A second (identical) DFC-1 display can (optionally) be connected to the CTRL2 socket, but it can only be used for monitoring purposes (not for controlling the DF-5).

Additional (optional) accessories can be connected to the AUX socket and to the EXPANSION PORT at the right half of the front panel. Power – typically from the 12V or 24V car battery, or from an external power supply unit (PSU) – is connected to the POWER socket at the bottom centre. The device is switched ON by means of the rocker switch at the bottom of the DFC-1 display unit.

Click to see more

At the left are 4 BNC sockets for connection of the antennas. The largest one – the reference antenna – should be connected to socket (4), whilst the smaller direction finding antennas – the stubs – should be connected to sockets (1), (2) and (3). In the device shown above, a gyroscope is fitted below a rectangular panel at the top, marked with a big white arrow (more about it below).

Click to see more

The DF-5 is fully controlled with the DFC-1 display unit shown above. It should be connected to the CTRL1 socket of the DF-5. It comprises an 8-button keypad, a speaker, a 16-digit alpha­numeric display and a bearing display, also known as the rose. The rose consists of a series of LEDs in a circular arrangement, pointing in the direction of the transmitter. To the right of the rose is the signal strength indicator, which consists of three LED bars in green, orange and red.

A small speaker is embedded in the front panel of the DFC-1. It is used for producing the key-clicks (when operating the keypad) as well as for reproducing the audio from the DF-5. The audio volume can be controlled with the knob at the top. At the bottom right is the ON/OFF switch.

Fixed direction finding
The DF-5 was used as part of a series of unmanned fixed Direction Finding stations, known as meridians, located at strategic positions throughout the country. The information from these locations was sent by means of modems to the command and control room of the police, where it was plotted on a map. From there, it was distributed to the relevant regional investigation teams.

Mobile direction finding
Once the fixed DF station(s) had roughly determined the position of the tracked vehicle, a special tracking vehicle could be deployed to search more closely. These unmarked police cars – usually a regular inconspicuous sedan – had a DF-5 receiver installed in the trunk, whilst the DFC-1 remote control unit/display was mounted on the dashboard, as illustrated in the diagram below.

Example of a police tracking vehicle

For proper direction finding, the DF-5 has to be used with 3 or 4 antennas, one of which is used as the refererence antenna. The other antennas, known as stubs were available in several forms, so that they were not recognised as such. In most cases, disc antennas were used for the stubs, as they could be hidden in the sunroof of the car. This is illustrated above as S1, S2 and S3.

The 4th antenna – the reference antenna – was placed further towards the rear of the roof (R4), and looked like a typical cellphone antenna of the era. In The Netherlands such antenna's were commonly used with the analogue (1G) mobile telephone network ATF-3. In most cases, dual-band disc antennas were used for S1 and S2, so that the vehicle could be used for tracking beacons in the 2m and 8m band. For the 8m band, only three antennas were used (S1, S2, and R4). For tracking beacons in the 2m band, all four antennas were used (S1, S2, S3 and R4).


When the DF-5 is used in a driving vehicle, it is important that the arrow of the gyroscope points in the forward (driving) direction. If the device will be placed horizontally, the gyroscope has to be mounted into the top cover. If the device will be used vertically, the gyroscope has to be fitted into the centre compartment at the rear of the device. The electronic gyroscope can be fitted in four different orientations, so that the DF-5 can be placed in all possible positions (N, E, S, W).

Portable direction finding
When getting close to the tracked vehicle, the tracking vehicle often had to be abandoned, as other­wise it might attract the target's attention. In such situations, the observation teams (OT) used a portable miniature receiver, such as the single-channel SRX-1, to do the last bit on foot.

Front panel
Antenna sockets
Power and audio sockets
Interfaces
Configuring the gyroscope
DF-5 with gyroscope fitted at the rear
DFC-1 display connected to DF-5 direction finder
Volume knob at the top of the DFC-1 unit
B
×
B
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Front panel
B
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Antenna sockets
B
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Power and audio sockets
B
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Interfaces
B
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Configuring the gyroscope
B
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DF-5 with gyroscope fitted at the rear
B
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DFC-1 display connected to DF-5 direction finder
B
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Volume knob at the top of the DFC-1 unit

Improvements
The DF-5 has a number of improvements over its predecessor, the DF-4:

  • Suitable for all frequencies between 25 and 500 MHz (not restricted to one band)
  • Suitable for tracking beacons outside the police bands
  • Ability to scan an area for alien beacons
  • Support beacons from foreign law-enforcement observation teams
  • Double sensitivity (+6dB)
  • Built-in PET stabiliser
PET stabiliser
Although a correlative interferometer gives a much more accurate bearing to the transmitter than conventional direction finding techniques, such as Watson-Watt or even Doppler, the reading can be erratic in urban environment, especially in earies with large concrete or steel structures.

For this reason, the DF-5 is equipped with a so-called PET 1 stabiliser – a device that intelligently filters the bearing data, before presenting it on the display. This is done by using an additional computer platform that applies low-pass filtering, and that takes the movements of the tracking vehicle itself into account by using data from a motion sensor and an electronic gyroscope.

For the older DF-4, the PET stabiliser was available as an external add-on, that was connected between the CTRL1 port of the DF-4 and the DFC-1 display. In the DF-5 it is an integral part of the unit, that is fitted internally on top of the main computer board. The front panel connectors (CTRL1, CTRL2, AUX and EXPANSION) are all provided by the PET board. The PET was developed in 1992 and is described by David A. Tong in US Patent 5,280,293 of 11 Sep 1992.  Leaflet

  1. PET = Performance Enhancer for Tracking.

Compatible beacons
D-902
D-902
Second generation beacon D-903
Parts
Leather briefcase
DF-5 receiver
DFC-1 display unit (rose)
Covert beacon (tracker)
CMD-3 Telecommander (remote control unit for beacon)
Antennas
Operating instructions
Moving map display
Map
Leather briefcase
The DF-5 was usually supplied in the unbtrusive leather pilot briefcase shown in the image on the right. Is measures 385 x 210 x 485 mm and has two leather pockets at the short sides.

It offers space for the display unit, the antennas, the cables and any optional devices, such as the CMD-3 telecommander and external expansion interfaces.
  
Leather carrying case

Receiver   DF-5
The actual DF-5 receiver is housed in the milled aluminium enclosure shown in the image on the right. It has large removable lids at the top and bottom, plus three smaller ones at the rear. All connections are at the front panel. The device is usually supplied in the leather pilot case shown above, but can also be used outside the case.

It is imortant that it is installed in the tracking vehicle, with the large white arrow pointing in the forward (driving) direction. The receiver is controlled from the DFC-1 display unit.

 Look inside the DF-5

  
Datong DF-5 direction finder

Display   DFC-1
All controls and indicators of the DF-5 are on the external DFC-1 unit shown in the image on the right. It should be connected to the CTRL1 socket of the DF-5, and shows the bearing to the transmitter. All user interaction is via this unit.

If necessary, a second DFC-1 unit can be connected to the CTRL2 socket of the DF-5, but this extra unit cannot be used for controlling the receiver. It is for displaying only.

 Look inside the display

  
Remote control unit (DFC-1)

Beacon   D-903
The DF-5 is entended for use in combination with intelligent second-generation tracking beacons, such as the Datong D-902 and (better) the D-903 shown in the image on the right.

The beacon is housed in a milled aluminium enclosure and is powered by an internal lithium battery pack. It has a series of twelve strong neodymium magnets at the rear, allowing it to be covertly attached to (or under) a vehicle.

 More information

  
Datong D-903/TRSI beacon

Telecommander   CMD-3
Intelligent beacons fitted with a receiver, like the D-903/TRSI shown above, can be configured and controlled remotely, by means of the CMD-3 telecommander shown in the image on the right.

The telecommander can be used to alter the operating mode of the beacon (continuous or pulsed), and can be used to enter sleep, deep sleep or coma mode, in order to reduce the chance of detection by the targeted party.

 More information

  
CMD-3 telecommander with helical antenna

Antennas   wanted
The reference antenna was usually disguised as a regular car phone antenna of the era. The actual direction finding antennas – the stubs – were available in several forms, such as a roof rack, or as plate antennas with a magnetic base.

The most popular solution however, was to use three disc antennas that were installed below the blinded window of a sunroof. The image on the right shows a typical car phone antenna of the era. We are unable to show the original covert disc antennas at this time.

  
Example of a car phone antenna of the era

Manual
Each DF-5 came with a full set of manuals, one for the DF-5 itself and one for each of the other parts, such as the tracking beacons and the telecommander. We do have these manuals in our collection, but as they contain written – potentially confidential – information, we are unable to disclose them at this time.

 Overview of documentation
  

Moving map
Data from DF-5 units in fixed stations could be sent by MODEM to a central facility, where it was plotted on a map. In addition, when the DF-5 was used in a moving vehicle, the current location and the measured bearing could be projected onto a local moving map display.

Datong produced a PC-based environment for this, known as NAVIGATOR, but police services also used in-house developed software. The DF-5 is also compatible with the Becker Avioscout — a map display for airplanes and helicopters.

  

Leather carrying case
Remote control unit (DFC-1)
DFC-1 display connected to DF-5 direction finder
Volume knob at the top of the DFC-1 unit
C
×
C
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Leather carrying case
C
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Remote control unit (DFC-1)
C
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DFC-1 display connected to DF-5 direction finder
C
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Volume knob at the top of the DFC-1 unit

Block diagram
The simplified block diagram below shows how the DF-5 works. At the top left are four antennas: three small stubs – S1, S2 and S3 – and a larger one – the reference antenna (R4). The antennas are connected to four highly identical receivers (1-4). The four receivers have a common Local Oscillator (LO) — in fact a Beat Frequency Oscillator (BFO) — so that they are tuned in tandem.

The outputs of the four receivers are fed to four lock-in amplifiers that are driven by a common I/Q signal that is derived from the reference receiver (4). Each lock-in amplifier provides a pair of DC voltages that represent the phase of the associated receiver, relative to the reference channel.


The DC voltages are low-pass filtered – to remove noise – and converted to the digital domain (i.e. digitised) after which they are processed by an internal computer. The system is calibrated by a built-in calibration oscillator of which the signal can be fed directly to the antenna inputs. This way, the software can cancel out any differences between the receivers. The distances between the antennas can be entered into the computer's non-volatile memory, allowing the software to calculate the correct bearing from the measured phase differences. As a final step, the system is calibrated with a real beacon that is placed at some distance in front of the tracking vehicle.

The computer communicates via a serial bus with a built-in PET stabiliser, which in turn provides the interfaces to the outside world. Display(s) and optional expansions are connected to the PET. The PET also has a built-in motion sensor and an electronic gyroscope, so that it can compensate for the movements of the tracking vehicle itself when presenting the bearing on the display.


Interior
The DF-5 is housed in a milled aluminium enclosure that has compartments at the top, bottom, front and rear. The compartment at the top is covered by a large panel that is held in place by 12 recessed screws at the top. After removing the screws, the panel can be taken off, as shown here:

Interior of the DF-5 seen from the top

Two board are fitted in this compartment: the computer board – which fills the entire space – and a smaller PET board that is fitted on top. The computer board is connected to the receivers at the bottom. It comprises an Intel TN80C196 microprocessor with RAM, an EPROM with version 4.3 of the firmware, battery backed CMOS RAM (settings), and lots of 4th and 6th order low-pass filters.

The PET board takes about 2/3rd of the space and is fitted on top of the computer board. It is a fully autonomous unit that communicates with the computer board via a serial RS232 interface, and to the outside world (e.g. the DFC-1 display) via several further RS232 interfaces. It has its own Intel 80C196 microprocessor with RAM, EPROM and battery backed CMOS RAM to hold the user's settings. The board contains a motion sensor, and is connected to an electronic gyroscope that is fitted either in the top panel or the rear panel. These motion sensors are used to take the movements of the tracking vehicle into account when presenting the bearing data to the display.

Interior of the DF-5 seen from the bottom

The large compartment at the bottom of the DF-5 holds the receivers, the local oscillator (LO), the I/Q modulator and the lock-in amplifiers. The latter provide the signals for the analogue filters on the computer board. All circuits are shielded by tightly soldered metal cans, as a result of which we are unable to see their contents. The circuits are interconnected with high quality coaxial cables with SMB connectors. At the rear are the control lines from the computer board.

The diagram above also shows the three milled-out compartments at the rear of the enclosure. At the right is the power converter. At the left is the ribbon cable that feeds the control signals from the computer board to the receivers. The gyroscope must be fitted into the compartment at the centre when the device will be used in the upright position. In this case it is fitted at the top.

Interior of the DFC-1 display (disassembled)

The DFC-1 display unit is housed in a customised standard die-cast aluminium enclosure that consists of two shells, with flat inserts at the top and at the bottom. The insert at the bottom holds the sockets and the ON/OFF switch, whilst the one at the top holds the volume control.

The bottom case shell holds the processor board with two daughter cards: a small one with the 16-character alphanumeric LED display, and a larger one with the bearing indicator, or rose, that consists of a circular array of LEDs. To the right of the rose are three rows of green, yellow and red LEDs that form the signal-strength indicator (S-meter}. The circuit comprises a 87C51 micro­controller and two MM5450N LED and Display Controllers. The main board also holds two audio amplifiers – one for the receiver and one for the key-clicks – and some logic for the serial port.

The upper case shell holds the keypad, a small speaker and two windows: a large grey one for the rose, and a narrow red one for the 16-character LED display. Adhesive foam pads are present at several positions to keep the windows in place. The two case shells are held together with four large bolts in the corners of the rear side. The DF-5 is enabled with the ON/OFF rocker switch.

Interior - top side
Interior - bottom side
Interior seen from the rear bottom
Interior - top side
Part of the computer board
Main board seen from the left side of the device
Backup battery on the computer board
PET board
Motion sensor
Connections to the front panel and to the computer board
Electronic gyroscope
Gyroscope removed from the DF-5
Power converter
Electronics mounted behind the front panel
Front panel antenna socket circuitry
Front panel connectors wiring
DFC-1 interior
DFC-1 interior
Disassembled DFC-1 display/control unit
Processor and LED/Display drivers
DFC-1 processor board and connectors
Keypad - solder side
Cable between DF-5 and DFC-1 display
DFC-1 display connected to the DF-5
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×
D
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Interior - top side
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Interior - bottom side
D
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Interior seen from the rear bottom
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Interior - top side
D
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Part of the computer board
D
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Main board seen from the left side of the device
D
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Backup battery on the computer board
D
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PET board
D
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Motion sensor
D
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Connections to the front panel and to the computer board
D
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Electronic gyroscope
D
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Gyroscope removed from the DF-5
D
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Power converter
D
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Electronics mounted behind the front panel
D
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Front panel antenna socket circuitry
D
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Front panel connectors wiring
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DFC-1 interior
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DFC-1 interior
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Disassembled DFC-1 display/control unit
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Processor and LED/Display drivers
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DFC-1 processor board and connectors
D
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Keypad - solder side
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Cable between DF-5 and DFC-1 display
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DFC-1 display connected to the DF-5

Restoration
When we received our DF-5, it was incomplete and in unknown condition. Luckily it came with the original operating instructions, which greatly helped in determining the working principle of the device. As the receiver had previously been used in a tracking vehicle, most of the cables and the stub antennas had been lost, but these could easily be replaced by non-resonant alternatives.

Furthermore, the device had been in storage for nearly 20 years after it was decommissioned in the early 2000s, as a result of which the backup batteries were likely to be exchausted by now. This means that channel settings, calibrations and user settings were likely to have been lost.

One of the first things that needed our attention was the power socket, which is located at the centre of the front panel. For reasons that are beyond our comprehension, the manufacturer has choosen to use a 3-pin XLR socket for this and (worse) to use an unconventional wiring.
  
Modified power socket with 4-pin XLR

On the DF-5, the (+) terminal is connected to pin (1) of the XLR3/P, whilst in most countries this pin is used for the (-) terminal. With lack of a proper wiring standard, and to avoid damage as a result of accidentally plugging in the wrong cable, we decided to swap it for an XLR4/P part.

Next, the interconnection cable between the DF-5 and the dispay unit was restored. The orginal 9-pin D-sub connector had been swapped for a diferent one by a previous owner, for easier installation in a vehicle. The correct wiring of the 9-pin connector was deduced from the internal wiring of the PET board, and was later verified against the wiring specified in the user manual of another Datong direction finder — the DF-6.

Together with the DCF-1 display unit, this cable is a minimum requirement to bring the DF-5 to life. It should be connected to the CTRL-1 port.
  
Cable between DF-5 and DFC-1 display

With all cables in place, the newly made power cable was used to connect the DF-5 to a 12V DC power source. An old carphone antenna with magnet mount was used as the reference antenna, and short improvised helical antenna's were used as stubs. We also used a signal generator to simulate a beacon. After switching the system ON (with the rocker switch at the bottom of the display unit), the device came alive and immediately produced a bearing on the display (rose).

Fixed
So far, the following restoration work has been carried out:

  • Leather case cleaned
  • DF-5 exterior and front panel cleaned
  • Cable between DF-5 and DFC-1 reconstructed
Missing
  • Disc antennas
  • Technical documentation
DFC-1 display connected to the DF-5
Modified power socket with 4-pin XLR
Cable between DF-5 and DFC-1 display
E
×
E
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DFC-1 display connected to the DF-5
E
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Modified power socket with 4-pin XLR
E
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Cable between DF-5 and DFC-1 display

Connection
Power
Below is the pinout of the 3-pin male XLR receptacle at the centre of the front panel, which is used for the power input. Note that this connector is not wired as expected, and has the (+) terminal on pins 1 and 2, and the (-) terminal on pin (3). This is different from other equipment.

  1. +8 to 30V DC (typically +13.5V)
  2. +8 to 30V DC (typically +13.5V)
  3. 0V (ground)
    Standard wiring of the male XLR3 receptacle at the front panel, when looking into the connector.
As there is no proper standard for wiring an XLR3 (audio) connector for supplying DC power, its use it strongly discouraged. In order to avoid confusion and potential damage to the equipment by plugging in the wrong cable, we have decided to replace the socket by a 4-pin XLR4 and wire it according to international conventions. Below is the pinout when looking into the socket.

  1. 0V (ground)
  2. not connected
  3. not connected
  4. 12V (ground)
    Wiring of the alternative (better) male XLR4 receptacle
WARNING — Note that an unconventional wiring scheme is used for the power socket. Check the power cord and ensure which pin is connected to the chassis, before connecting the DF-5 to a 12V DC power source.
CTRL 1
The CTRL1 port is used for connection of the primary DFC-1 display, which is also used to control the receiver. It communicates with the DF-5 via a 9600 baud 8N1 RS232 interface. If necessary, a second DFC-1 display can be connected to the CTRL2 socket, but this cannot be used for controlling the DF-5 receiver. Below is the pinout when looking into the socket:

  1. +12V
    brown
    when DF-5 is switched on
  2. TDX
    pink
    to RXD of DFC-1
  3. n.c.
    -
    not connected
  4. ON
    yellow
    when connected to ground
  5. Audio
    green
    to DFC-1
  6. 0V
    black
    Ground
  7. RXD
    grey
    from TXD of DFC-1
  8. n.c.
    -
    not connected
  9. GND
    blue
    Audio ground
CTRL 2
If necessary, a second DFC-1 display can be connected to the CTRL2 socket, and can be placed for example near the driver seat. Note that the second display cannot be used for controlling the DF-5 receiver. This can only be done from the primary display that is connected to CTRL1.

  1. +12V
    brown
    when DF-5 is switched on
  2. TDX
    pink
    to RXD of DFC-1
  3. n.c.
    -
    not connected
  4. ON
    yellow
    when connected to ground
  5. Audio
    green
    to DFC-1
  6. 0V
    black
    Ground
  7. RXD
    grey
    from TXD of DFC-1
  8. n.c.
    -
    not connected
  9. GND
    blue
    Audio ground
AUX
This port is intended for the connection of optional expansion units, such as an antenna switcher and a tracker command transmitter (telecommander). The wiring of this connector is currently unknown, but it is assumed that it provides a 9600 baud 8N1 RS232 interface as well as power.

  1. ?
  2. ?
  3. ?
  4. ?
  5. ?
  6. ?
  7. ?
  8. ?
  9. ?
Expansion port
This port was intended for future expansions. The wiring of this connector is currently unknown, but it is assumed that it provides a 9600 baud RS232 interface with modem lines as well as some digital lines, and probably also a 12V power supply. Pinout when looking into the socket:

  1. ?
  2. ?
  3. ?
  4. ?
  5. ?
  6. ?
  7. ?
  8. ?
  9. ?
  10. ?
  11. ?
  12. ?
  13. ?
  1. ?
  2. ?
  3. ?
  4. ?
  5. ?
  6. ?
  7. ?
  8. ?
  9. ?
  10. ?
  11. ?
  12. ?
Display   DFC-1
Below is the wiring of the 7-pin DIN socket at the bottom of the DFC-1 display/controller, when looking into the socket. Note the strange numbering of the pins. This socket should be connected to the CTRL1 socket on the DF-5 (see above). Pinout when looking into the socket:

  1. RXD
    pink
    Data from DF-5
  2. Audio
    green
    Audio from DF-5
  3. TXD
    grey
    Data to DF-5
  4. ON
    yellow
    Switched to ground
  5. GND
    blue
    Audio return
  6. +V
    brown
    Power supply (from DF-5)
  7. 0V
    black
    Power GND (chassis)
Specifications
  • Type
    Correlative interferometer radio direction finder
  • Purpose
    Beacon tracking
  • Users
    Law enforcement agencies
  • Receivers
    4
  • Frequency
    25 - 500 MHz
  • Steps
    10 Hz
  • Channels
    100
  • Sensitivity
    -152 dBm
  • Bandwidth
    100 Hz - 8 kHz in 8 steps
  • Stabiliser
    PET (standard)
  • Power
    8 - 30V DC
  • Dimensions
    365 x 333 x 107 mm
  • Case
    485 x 385 x 210 mm
  • DFC-1
    200 x 90 x 28 mm
  • Weight
    10 kg
Antenna options
  • Reference antenna (cell phone antenna)
  • Ski-rack antenna
  • Antenna pattern
  • Disc antenna
  • Plate antenna
Optional extensions
  • 50-GPSPSU-0010
    GPS receiver with RS232 interface (AUX)
  • ?
    Antenna selector
  • DIRECTOR
    PC with moving map display software
  • ?
    Telephone modem
Documentation
  1. DF-5 Leaflet
    Datong, October 1993. CM303606/R.

  2. PET Stabiliser leaflet
    Datong. PET.PM3 2990. Date unknown.

  3. User Guide for DF-5
    Datong, 20 August 1993 (based on 1st draft of 19 May 1993).

  4. User Guide for Beacon System model D-903
    Datong, 19 February 1992. Issue 1.1.

  5. User Guide for Second Generation Command Transmitter, Model CMD-3
    Datong, Issue 1.3, 5 February 1992
References
  1. Anonymous donor, Datong DF-5 direction finder - THANKS !
    Received December 2020.

  2. Original order confirmation 1
    30 September 1993. In Dutch language.

  3. US Patent 4,809,012, Direction Finding Equipment
    David A. Tong, filed 27 May 1987.

  4. US Patent 5,280,293, Mobile Direction Finder
    David A. Tong, filed 11 September 1992.
  1. Confidential document. Not for public release.

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Crypto Museum. Created: Thursday 21 January 2021. Last changed: Monday, 06 September 2021 - 12:37 CET.
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