Doppler Systems offers direction finder components that can be paired with your narrow band FM receivers to create an accurate, low-cost radio direction finder (RDF). Our direction finder components include processors and fixed site and mobile antennas.

DDF7000 Series DF Processor

The 7000 series is our latest generation of radio direction finding components. It is based on a solely digital signal processor packaged in a small faceless package.  You can use the same processor with a wide variety of receivers for either fixed site or mobile operation. Additionally, a Windows-based software suite is provided with the unit enabling the user to display lines of bearing on a map in real time. The system is fully compatible with networks using our legacy Series 6000 or 6100 direction finders.

Features of the DF Processor

• Fixed site antennas have very broad bands. Therefore, this processor increases accuracy and sensitivity.
• The DDF7000 Series DF Processor is useful for mobile or fixed site applications.
• The single antenna control cable and coax seamlessly cover 115 to 1000 MHz.
• The processors may be ganged to monitor multiple frequencies.
• The USB interface supports receivers like the ICOM R1500, R2500, R8600, R30, and AOR SR2200. With USB-to-serial adapters, it supports RS232 receivers (AOR AR8600, AOR AR5000,AOR AR5001, ICOM R8500, ICOM R9500).
• It can be used with any narrowband FM receiver that has an external speaker connection.
• Direct connectivity to Ethernet enables remote operation without local PC or network adapter.
• It contains a built-in web browser interface for adjusting settings.
• Streaming audio available via Ethernet allows remote monitoring and recording.
• The DDF7000 Series DF Processor is directly networkable via intranet, Internet or radio modem.
• It can be used in same network as DDF6001 and DDF6002 direction finders.
• The bearings may be time tagged and synchronized by connecting a GPS.
• Additionally, this processor is small, light weight, and low power.
• The processor contains a field upgradable flash memory.
• Finally, map-based software is capable of geolocation when using multiple direction finding sites.

Fixed Site DF Antennas

Our fixed site antennas cover 115 – 1000 MHz in three bands.  These are available as single band, dual band, or triple band (THF over UHF over VHF) stacked arrays.  Biconical elements contribute to excellent broadband performance over the entire frequency range of each antenna.  Each array consists of 8 biconical dipoles at the end of the arms and balun connected for high radiation efficiency over the entire octave band.

Connectors used are TNC for the RF and MIL-C-38999 Series 3 for the control. Masts, connecting cables between stacked arrays, and clamping hardware are provided for each of the available fixed site arrays. Masts are constructed of fiberglass and cables are ferrite isolated in order to minimize interaction with the active elements in the array. Cable sets between the antenna and the processor/receiver are available in multiples of 25 – 300 feet and include ferrite isolators.  In addition, the switches in the antennas require only one coaxial cable and one control cable to be run to the base of the lower antenna in the array.

Antennas are factory calibrated to provide the accuracy figures listed below. Overall size and weight are also listed. These are for the arrays themselves and do not include the base, mast, and cables.

Specifications

Model	Description	Frequency Range (MHz)	Accuracy (deg rms)	Diameter (inches)	Height (inches)	Weight (lbs)
DDF7091	VHF ( 8 element )	115 – 250	1.0	39	40	13.6
DDF7097	VHF ( 4 element )	115 – 250	2.5	30	40	6.0
DDF7092	UHF ( 8 element )	250 – 500	1.0	17	16	8.6
DDF7093	THF (8 element )	500 – 1000	1.6	9.5	6.5	8.2
DDF7094	VHF/UHF Stack	115 – 500	1.0	39	61	24.7
DDF7096	UHF/THF Stack	250 – 1000	1.0	17	25	18.7
DDF7095	VHF/UHF/THF Stack	115 – 1000	1.0	39	70	35

Mobile DF Antennas

For mobile operation below 500 MHz, place our mobile summing unit (DDF7080) on the roof of a vehicle with a set of four matched quarter-wave magnetic mount antennas arranged in a square.  The spacing is a quarter-wave length nominally.  For single band operation, the user can cut the antennas to resonate at the band center to achieve the best performance over a given bandwidth.  Above 500 MHz, the THF (DDF7064) antenna hosts four stub types directly mounted to the summing unit. This includes a separate ground plane, cover, and safety strap. 

By switching antennas or by using multiple antennas and summers, you can accommodate multiband operation. To switch these, simply unscrew the whips from the magnetic mount bases. Next, mount different length whips to the bases and reposition.  If this is not possible or if you anticipate frequent band switching, you can also use multiple summers with multiple antennas in a similar fashion to the fixed site arrays. The summing unit accomplishes all switching so that only one control cable and one coaxial cable route into the vehicle.

We also offer a pod antenna that covers 100 – 1000 MHz. While the antennas are mounted on a ground plane, the summers are mounted beneath the ground plane.  The ground plane sits atop the vehicle on four feet and is strapped or permanently attached to avoid blowing off when driving.  In addition, a plastic cover is available to enclose the entire assembly.