Fixed Direction Finding

ELT Tracking Direction Finding

The Techtest DF system is designed to reduce the time to trace emergency locator beacons, thus reduce the time taken to rescue casualties or those in distress. Traditional homing systems are less efficient and far less cost effective, due to high fuel consumption and longer flight times.

 It is compatible with both 121.5MHz swept tone distress beacons and 406MHz COSPAS-SARSAT transmissions on current and future frequencies, future proofing the design of the product. The user is able to monitor four frequencies and detect emergency transmissions. Each transmission is allocated a unique identification which can then be selected for more detailed information. For 121.5MHz the system can display relative bearing details. For 406MHz the system will give all the same information as 121.5MHz but in addition will record and decode the COSPAS-SARSAT message, giving details of the distress beacon and if available the GPS beacon location. The system comprises of three modules

  • 1. Antenna (10-246-1)
  • 2. Control Unit (406-28)
  • 3. Display (407-3)
Detection:  In normal operating mode the DF receiver frequency is switched cyclically between 121.5, 156.8 and 243 MHz If a signal above the threshold is detected, a 0.3 second snapshot is recorded before continuing. A separate receiver is used to continuously monitor the 406 SARSAT frequency. If a signal is detected then the DF receiver will immediately switch to 406MHz frequency and record a snapshot. In the event of transmitting beacons incorporating a GPS position, the system will display the applicable lat/long co-ordinates.

Direction Finding / Homing:  A 360˚ direction finding facility is provided giving a direction for the aircraft to fly to the transmitting beacon. No other navigation aids are required. If however on board GPS navigation systems are installed in the aircraft, system integration will provide aircrew with both an absolute bearing and distance information to the transmitting beacon. In the Homing mode the system sequentially scans the distress frequencies and provides a visual display of left/right steer information.

Cockpit Controller / Indicator: The controller / indicator is mounted in the cockpit. There are just two controls: a push button mode selector (switching between Decode and DF modes), a rotary click / push selector providing control of menu options. The unit is designed to operate mainly without user input.


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