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The 6100 series radio direction finder provides a self contained system for mobile triangulation. Utilizing the AutoTrack software program running on the user's laptop computer, lines of bearing may be recorded on a digital map. A GPS receiver is used to measure the tracking vehicle's location and heading which are displayed as an icon on the map. Lines of bearing (LOB) are also shown on the map originating from the icon. When the user determines that a valid bearing is displayed, the LOB is stored and the icon changes. By driving to another location and taking another LOB, the intersection indicating the emitter location is found. This process continues as the tracking vehicle closes on the emitter. The number of LOBs displayed may be limited to show only the most recent; however, all selected LOB data is written to a file that may be recovered later for analysis of the data.
The system is based on the DDF6002 display/processor unit which uses advanced digital processing to estimate the bearing angle. In addition, it provides the data multiplexing required to interface the GPS receiver, NBFM receiver, and optional flux gate compass with the laptop computer through a single serial RS232 port. The DDF6072 distributes 12 VDC power to all of the equipment and the DDF5948 provides an integrating roof mounting platform for the direction finder antenna, RF summer, GPS antenna and optional compass. The figure below shows a block diagram of the complete system using the DDF5948 roof pod.
The roof pod provides a low profile integrated mounting that is desirable in covert applications. If this is not needed, and if the optional compass is not used, the series 6100 may be used without the pod. This is shown in the following block diagram.
The DDF6002 display/processor drives the rf summer with the waveforms required to mix the four antenna inputs smoothly and to produce the simulated Doppler modulation at the selected sweep frequency. Audio from the receiver is processed to calculate a best estimate of the bearing angle in either a continuous or pulse mode. The DDF6002 may be used as a standalone homing type radio direction finder or it can be used with the AutoTrack software as a triangulation system. When used with the DDF5948 antenna and an Icom R7000/7100/8500/9000 or equivalent receiver, the DDF6002 meets the following specifications:
AutoTrack is provided with the DDF6002 direction finder.
This laptop software runs under Windows 95 on an IBM 486 or later PC having 8 MB RAM. The program accepts any bit mapped image (*.BMP file). Serial data from the DDF6002 is decoded into the bearing angle, GPS latitude, longitude, heading and velocity. When a compass is used, AutoTrack uses its heading when the velocity is less than 5 km/hr; otherwise the heading is obtained from GPS. The tracking vehicle is located on the map image and displayed as an icon. The true bearing direction is displayed as a line from the icon on the map and is saved when the user presses the Insert key.
The program also provides control of the direction finder front panel controls and the receiver's frequency. A convenient auto-calibration can be set up if the location of a beacon transmitter (for example, a NOAA weather station) is known. The following screen image is taken from the AutoTrack demonstration program (which may be downloaded from the Software/Upgrade page).
The DDF6074 is a compatible GPS receiver and antenna. The receiver is made by Garmin and is preprogrammed to provide the NMEA0183 messages GGA and VTG every 1 second. The GPS cable is wired to connect to a DDF6002 RS232 input and to the DDF6072 for power.
The DDF6075 compass is a version of the KVH model C100 which is recommended when operation is required when the tracking vehicle is stationary. (GPS does not provide heading information when the tracking vehicle velocity is less than a few km/hr). NMEA0183 message HDG is sent from the compass every 1 second. The DDF6075 includes compatible connectors for the serial data and power used in the series 6100 system.
The DDF5948 provides a low profile integrated antenna platform for mobile radio direction finding with the series 6100. The pod attaches to the car by two quick disconnect straps that pass though the door frames or windows. A black removable cover is held to the pod mounting frame with four locking type clamps. Antenna whips which protrude through the cover have a black coating which makes the entire pod very inconspicuous for covert use.
The pod comes with precut antennas and prewired antenna mounts that provide coverage of the most popular frequency bands. Note that although the performance specified for the DDF6100 is based on the use of a narrow band FM receiver (NBFM), it is possible to obtain bearings with an AM or even wide band FM (WBFM) receiver under certain conditions. The DDF5948 antenna provides the proper combination of antenna spacing and element length to allow AM and WBFM operation although the performance will be degraded from that obtained in the NBFM mode.
Frequency (MHz) |
Antenna Elements |
Antenna Mounts |
88-108 (WBFM) |
686 mm (27 inch) whip |
5/16-24 stud mounts on 538 mm (21.2 inch) square |
108-136 (AM) |
||
125-175 (NBFM) |
445 mm (17.5 inch) whip |
5/16-24 stud mounts on 269 mm (10.6 inch) square |
175-250 (NBFM) |
||
250-350 (NBFM) |
5/16-24 stud mounts on 135 mm (5.3 inch) square |
|
350-500 (NBFM) |
152 mm (6 inch) whip |
|
500-700 (NBFM) |
TNC mounts on 76.2 mm (3.0 inch) square |
|
700-1000(NBFM) |
73 mm (2.875 inch) stub |
Changing antennas is accomplished by simply moving the four TNC coax patch cables on the upper side of the ground plane and removing/installing the antenna elements at the appropriate mounts. Beginning in 2005 our roof pod antennas were made to allow up to three pod RF summers - one in the center and two towards the front. Some of our customers prefer to use this arrangement which allows operation on three bands (125-175, 350-500 and 700-1000 MHz) without having to change the TNC patch cables. The 3-antenna switch DDF6079 can be used to control which RF summer and antenna set are selected automatically from AutoTrack or manually.
The DDF5948 provides several mounting locations for the DDF6074 GPS antenna and the DDF6075 compass.
The antenna ground plane rests on the car’s roof at four foam protected brackets. RF summer DDF5981 mounts below the ground plane at the center.
The roof pod is approximately 1044 mm (41.1 inches) square and 213 mm (8.4 inches) high. It weighs 16 kg (35 lb.).
The DDF5981 combines four antenna inputs in a way that adds frequency modulation at the sweep frequency to the incoming signal. It is electrically identical to the DDF5980 RF summer but has a flat bottom for mounting on the bottom surface of the DDF5984 roof pod ground plane.
The DDF5980 RF summer is used to combine four antenna inputs when the roof pod DDF5984 is not used. It has a strong magnet on its base for mounting on the vehicle's roof.
These antennas are sets of 4 matched magnetically mounted quarter wavelength whips which are arranged in a square pattern 1/8 to 1/4 wavelength on a side. The whip elements themselves may be ordered separately so that the same magnetic mounted bases can be used from 88 to 500 MHz.
| Model | Frequency Range (MHz) | Part Number of Whip |
| DDF6061 | 88 to 136 MHz | Q-88 |
| DDF6062 | 136 to 500 MHz | Q |
This antenna is a set of 4 broad band stubs, a ground plane and a plastic cover that mount directly on the DDF5980 RF Summer. A safety strap is also supplied.
The DDF6072 is a compact box that supplies 12 VDC power to the DDF6100 direction finder, receiver, laptop computer, GPS receiver and optional electronic compass. Twist lock connectors are used. The unit connects to the vehicle 12 VDC using a single auto power plug. A lithium battery is supplied for power backup of the DDF6074 GPS receiver allowing rapid startup after storage.