Antenna Authority, Inc
Phone (770) 577-7969




Product Code --- RFDF-3131 DF Monitoring System

An Accurate Compact Remote DF Monitoring System

The remote monitoring system is intended to be left running unattended to monitor and to take bearings on an intermittent, possibly clandestine RF radiator. The receiver is set to log bearings and audio data when a signal is active on the frequency of interest.  That information can be retrieved either directly or via remote access (if internet or phone is available) at a later date. The files are stored on a one minute basis to make retrieval easier and reduce the amount of lost time listening to unneeded audio. When an incident happens, the local people on-site need to record the time so the bearing and audio data can be retrieved efficiently.

          The RFDF 3131 System consists of the following equipment:

AADF-3101 DF processor

DASA-3131 antenna

AADF-3131 Chassis including all required cables

AR-8600 receiver

Laptop computer

Custom Control and mapping software – for both acquisition and retrieval

Uninterruptable Power Supply

Shipping Case(s) for deployment

The antenna is affixed on a mast - normally atop a building or a pole. The controls are mounted close by, ideally in an elevator shaft or somewhere secure, dry and close to the antenna.  Fifty feet of shielded, coaxial and control cable is provided with each system.

   The antenna is a dual band annular slot type enclosed in a vacuum ­formed, ruggedized, and lightweight abrasive resistant plastic cover with UV protection. The antenna is intended to be mounted on a 1.5” metal pipe (2’ aluminum section provided). All power and control signals to the antenna are provided through one 12 conductor control cable via the DF processor. The received signal with bearing information encoded is routed to the receiver through an RF coaxial cable. The GPS receiver is located in the antenna and provides LAT/LON for the mapping and timestamp for the bearings and audio. There is a compass mounted in the antenna for setting the original orientation on startup. The unit comes with shipping cases to make it convenient for shipping out for remote installation.


The software provided runs on the laptop and is intended to control the receiver and the DF which is monitoring the frequency of interest. When a signal is detected the audio and bearing information are logged.  It may be played back later on the same or a different computer to show the direction of the signal on a map. A licensed copy of Microsoft Mappoint is included.

RFDF-3131 Internal Wiring

Electrical Specifications

Frequency Coverage: 20 MHz - 1.0 GHz         Azimuth Coverage:    360° in azimuth

DF Technique:          Watson-Watt Phase      Antenna:       Dual Annular Slot

Bearing Accuracy:     6° rms                        Polarization:   Vertical

Power:                   115 VAC  300 watts Max

AOR Receiver 350 ma

AADF-3100 Processor  450 mA

Laptop  115 VAC, 250 Watts

RFDF-3131 External Wiring


Map of bearing LOBs for typical Weather station at 162.55 MHz
on Stone Mountain from Douglasville - 32 miles.

Mechanical Specifications

Antenna Dimensions:

 Diameter  24", Height: 5", Weight: 35 lbs


Operating Temp.: -40°C to +60°C,
Storage Temp.: -40°C to +70°C

Ordering Information    Model No. RFDF-3131
Downloadable PDF File

Specifications subject to change without notice

Printed in U.S.A. Copyright 9/1/2010
Specifications subject to change without notice

Antenna Authority offers a wide assortment of directional, wideband antennas and other equipment used for radio direction finding and Geo location. We are experts in covert antennas, vehicles and their operation. We are also ready to design new products to meet your specific needs.

Antenna Authority, Inc.                Ferrel Bentley - E-Mail
3381 W. County Line Road
Douglasville, Ga. 30135-1145
(770) 577-7969
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