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Doppler Systems LLC

Radio Direction Finders and Direction Finding Systems

Direction Finder Components

Doppler Systems offers components to allow a user to construct a radio direction finder to meet their needs.  Marry our radio direction finder components with your narrow band FM receiver to build an accurate, low-cost radio direction finder.

DDF7000 Series DF Processor

Doppler DDF7001 DF Processor
DDF7001 DF Processor

The 7000 series is our latest generation of radio direction finding systems which is based on an all digital signal processor packaged in a small faceless package.  The same processor may be used for either fixed site or mobile operation with a wide variety of receivers. 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.


  • Increased accuracy and sensitivity. Fixed site antennas are very broad banded.
  • Same direction finder processor can be used for mobile or fixed site applications.
  • Single antenna control cable and coax are used to seamlessly cover 115 to 1000 MHz.
  • Processors may be ganged to monitor multiple frequencies using one antenna.
  • USB interface supports receivers like the ICOM R1500, R2500, SR2200, R8600 and AOR SR2200. With adapters it supports RS232 receivers (AOR AR8600, AOR AR5000,AOR AR5001, ICOM R8500, ICOM R9500).
  • Any narrowband FM receiver with an external speaker connection can be used with it
  • Direct connectivity to Ethernet enables remote operation without local PC or network adapter.
  • Built in web browser user interface for adjusting settings.
  • Streaming audio available via Ethernet allows remote monitoring and recording.
  • Directly networkable via intranet, Internet or radio modem. Can be used in same network as DDF6001 and DDF6002 direction finders.
  • Bearings may be time tagged and synchronized by connecting a GPS.
  • Small, light weight and low power.
  • Field upgradable flash memory.
  • Map based software provides geolocation capabilities when using multiple direction finding sites.

Fixed Site DF Antennas

Our fixed site antennas cover 115 - 1000 MHz in three bands.  Antennas are available either as single band antennas, dual band or three band (THF over UHF over VHF) stacked arrays..  Biconical elements on the antenna 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 wide 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 fixed site antenna arrays available. 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 feet up to 300 feet and include ferrite isolators.  Antenna 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 below. These are for the antenna arrays themselves and do not include the base mast and cables.

Model Description Frequency Range (MHz) Accuracy (deg rms) Diameter (inches) Height (inches) Weight
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

Two Band VHF and UHF Fixed Site DF Antenna
DDF7094 Two Band VHF and UHF DF Antenna
Fixed Site VHF DF Antenna
DDF7091 VHF DF Antenna (115 - 250 MHz)
Fixed Site UHF DF Antenna
DDF7092 UHF DF Antenna (250 - 500 MHz)
Fixed Site 500 - 1000 MHz DF Antenna
DDF7093 THF DF Antenna (500 - 1000 MHz)
Three Band DF Antenna
DDF7095 Three Band DF Antenna (115 - 1000 MHz)
Three Band DF Antenna
DDF7097 Compact 4 Element DF Antenna (115 - 250 MHz)

Mobile DF Antennas

For mobile operation below 500 MHz, our mobile summing unit (DDF7080) is placed on the roof of the car with a set of four matched quarter wave magnetic mount antennas arranged in a square.  The antenna 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 type antennas directly mounted to the summing unit. This antenna includes a separate ground plane, cover, and safety strap. 

Multiband operation is accommodated by switching antennas or by using multiple antennas and summers.  To switch antennas the user would simply unscrew the whips from the magnetic mount bases, mount different length whips to the bases, and reposition the antennas.  If this is not possible or if frequent band switching is anticipated, multiple summers with multiple antennas can be used in a similar fashion to the fixed site antenna arrays.  All antenna switching is accomplished in the summing units so only one control cable and one coaxial cable are routed into the vehicle.

We also offer a pod antenna that covers 100 - 1000 MHz. The antennas are mounted on a ground plane with the summers mounted underneath the ground plane.  The ground plane sits atop the vehicle on four feet and is strapped on or permanently attached to keep it from blowing off when underway.  A plastic cover is available to enclose the entire assembly.

Mobile VHF DF Antenna
Mobile VHF DF Antenna
Mobile UHF DF Antenna
Mobile UHF DF Antenna
Mobile THF DF Antenna
Mobile THF DF Antenna
Dual Band Mobile DF Antenna
Dual Band Mobile Antenna
Pod DF Antenna (Cover Removed)
Pod Antenna (Cover Removed)
Pod DF Antenna on Vehicle
Pod Antenna on Vehicle