High Frequency Radio Direction Finder

Summary of Our High Frequency Direction Finders

Covering high frequency bands from 1.5 – 10 MHz, our high frequency radio direction finder (RDF) electronically creates a rotating directional antenna.  A simple AM receiver demodulates the received signal and our DF processor extracts the bearing information from the audio output of the receiver.  The system is optimized to work on near vertical incident skywave, NVIS, transmissions. It can locate all types of signals including AM, FM, SSB, any type of digital modulation, and even noise sources.

Loop Antenna

The receiving antenna are made by Wellbrook Communications. These loop antennae exhibit high bandwidth, low noise and compact size.  The loops are one meter in diameter and are mounted on tripods. The base stands approximately 2 meters off the ground.  The antennae are arranged so that the N, E, S, and W antennae are positioned in a square with a diagonal distance of 0.707 wavelength at the geometric center of the frequency band.  For a 4-8 MHz version this would be 123 ft.  In addition, the NS and EW loops are mounted near the center of the array. The loops are oriented to produce the same patterns as dipole antennae. For example, since the null in a loop is normal to the plane of the loop, antennae N, NS and S are all oriented in the NS plane. Antennae E, EW and W oriented toward the EW plane.


The high frequency radio direction finder uses our DDF7000 series processor and an AM receiver packaged. Doppler packages them in a portable Pelican case.  A single case holds two antennas and the requisite cabling.  For outdoor mounting, a weather-proof NEMA enclosure holds the summer/combiner.  We also provide a search receiver, which allows the operator to listen to the received signal.


Our TargetTrack and User interface software give the user easy display of the measured bearings. Users can link multiple systems in different locations via the internet to enable geolocation of a RF source within regional boundaries.

DF MethodSynthetic Directional Beam patented with “Smooth Summing”
Frequency Range1.5 – 10 MHz
Accuracy< 10 deg rms
Resolution0.1 deg
Sampling Rate2 samples per second
AveragingAdjustable from 1 to 20 samples
Rotation frequencyAdjustable (250, 500, 1000, 2000 Hz)
Voltage Range105 – 220 Vac (12 V power supplies furnished)
Power20 Watts
Temperature Range-25 °C to 85 °C (antenna)
CE CompliantPer EN 61000-6-2, EN 61000-6-4 AND EN 301 489-1
  • block diagram high frequency direction finder
  • high frequency antenna arrangement
  • high frequency direction finder loop
  • high frequency direction finder test