June 2, 2021

Mellori have been busy designing and manufacturing a Radio Direction Finder that allows for detection and location of emergency distress beacons.  The project was launched in response to a requirement by search and rescue agencies to fill a capability gap to monitor and find EPIRB signals in the legacy 121.5MHz & 243MHz frequency bands. 

Mellori Radio Direction Finder (MRDF) is designed to detect and pinpoint the direction of distress beacons (EPIRB) at a range greater than 30km, maximising the probability of quick location. Low power design gives more than 10 hours of continuous operation for situations where extended deployments are required.

The MRDF is a lightweight, field portable, purpose built, handheld direction finding unit specifically for the purpose of locating EPIRBs. The unit exceeded the requirement specifications offering simpler operation, lower weight, longer battery life and a line-of-sight detection range in excess of 32km. The sensitive receiver gives a single unit the potential to cover an area greater than 3200km2

When an EPRIB beacon is activated, it transmits a distress signal at a particular standard frequency which passing planes and emergency services monitor. Relevant authorities are notified of activity in this frequency band and will deploy teams to the approximate location of the reported signal to investigate.

Using a directional antenna which receives the highest signal strength when pointed directly at the signal source. By sweeping the antenna through 360 degrees it is possible to determine the direction of the transmitted signal. The beacon can be located by triangulation with regular direction checks performed whilst moving closer to the beacon.

The unit emits a tone proportional to the received signal strength whereby the higher the received signal, the higher the pitch. Since the human ear is very sensitive to small changes in pitch, it is quick and easy to locate the beacon by sweeping the antenna and listening for the highest pitch to determine the correct bearing. To guarantee the user is locked on to the correct signal it is also possible to listen to the actual emergency siren chirp the beacon emits.

MRDF is designed to be easy to setup and use thus reducing the operator training requirements. The intuitive user interface gives clear and simple feedback allowing the operator to quickly and effectively locate the emergency beacon transmissions.

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