Overview
The document describes the Direction Finding S.A.R. system by HR Smith Group, which incorporates real-time 406 decode capabilities. The system is designed to locate emergency locator beacons efficiently and is compatible with both 121.5MHz and 406MHz COSPAS-SARSAT transmissions.

System Components

• Antenna (10-246-1): A compact module with a circular array of elements and high sensitivity receivers, designed for optimal angular resolution.
• Control Unit (406-28): Processes array output using digital processing and beam forming techniques to discriminate multiple emitters and find signal directions.
• Display (407-3): Offers platform-specific display options, featuring a user-friendly interface with mode and scroll controls.

Detection and Direction Finding
The system operates by cyclically switching the DF receiver frequency between 121.5, 156.8, and 243 MHz, recording snapshots when signals are detected. A separate receiver monitors the 406 SARSAT frequency, switching immediately to 406MHz upon signal detection. The system provides a 360˚ direction finding capability, guiding aircraft to the transmitting beacon without additional navigation aids.

Cockpit Controller/Indicator
Mounted in the cockpit, it features a push button mode selector and a rotary click/push selector for menu options. It operates mainly without user input and offers three modes: Left-Right Indicator, Map Display, and Text Display.

Specifications

• SAR Frequencies: 121.5, 243, 156.8, 406 MHz
• Training Frequencies: 4 selectable from 110 to 410 MHz
• Sensitivity: 2.5μV
• DF Accuracy: Better than 5˚
• Decoder Frequency: 406.025 - 406.050 MHz
• Message Format: COSPAS-SARSAT C/S T.001
• Supply Volts: 18-36V DC MIL-STD 704D
• Environmental: MIL-STD 810F
• EMI/EMC: MIL-STD 461 F

Key Features
The system reduces the time to locate emergency beacons, is fully COSPAS-SARSAT compatible, and allows monitoring of four frequencies. It provides detailed information for 121.5MHz and 406MHz transmissions, including COSPAS-SARSAT message decoding and GPS beacon location if available.