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Ground SAR

DF systems mounted on land vehicles or used as man pack systems have to be lightweight, compact and very robust. They need to withstand any possible environmental stress because they are used in tough terrain. Man pack systems should be particularly frugal in current conditions.

RT-500-M SAR Direction Finder System for Rescue Missions at Sea

The RT-500-M is a multi-band direction finder system that operates on all frequency bands used for rescue missions. This direction finder automatically monitors the emergency frequencies 121.500 MHz, 243.000 MHz and 406.028 MHz (Cospas-Sarsat) as well as channel 16 of the marine band. The bright TFT display permits a clear overview of all direction finder information and operating parameters. A convenient menu structure makes it possible to adapt the RT-500-M direction finder system to the needs of the user. Various interfaces (LAN, NMEA RS-422, RS-232) facilitate integration of the direction finder system in legacy or planned system environments.



The RT-500-M direction finder system fully meets the steadily increasing needs of modern civilian and military search-and-rescue organizations. Emergency beacons that operate on the 406.028 MHz Cospas-Sarsat frequency can be reliably identified and localized. Like all RHOTHETA direction finder systems, the RT-500-M features complete MOB functionality to ensure the safety of SAR crew members. That makes the RT-500-M direction finder system a complete solution for professional SAR organizations.


Although the RT-500-M was optimized for use in high sea states, this direction finder system is also suitable for stationary VTS applications.

Ground SAR

Special Features

Universal multi-band direction finder: VHF aviation and marine band, UHF aviation band, Cospas-Sarsat frequency

Automatic monitoring of emergency frequencies during work on other frequency bands

High reception sensitivity to permit detection of extremely weak or distant signals

High direction finder accuracy, precise and stable display

LAN, NMEA, RS-422 and RS-232 interfaces for system integration and remote control

Optimized for use at sea: robust construction, waterproof (IP67) display/control unit and antenna

Compact broadband antenna system (Patent DE 4421759 C1)

Graphic TFT color display, especially bright (450 cd/m 2)

Remote control unit for exterior control platform with full control and display functionality

Complete illumination with automatic dimming as a function of ambient light conditions



Method of bearing Doppler-principle (3 kHz rotational frequency, right / left rotation)
Bearing Indication Relative bearing and True bearing (if ext. heading data available)
Bearing accuracy 5
Internal resolution 1
Sensitivity RF-voltage at receiver-input (50 Ohm): VHF < 100 nV; Marineband < 100 nV; UHF < 100 nV; 406 MHz < 150 nV
Frequency stability 2.0 ppm (?f/f=210-6) [in temperatur range -30C ... +80C]
Receiving bands 4 (VHF-Airband; VHF-Marineband, UHF-Airband; Cospas/Sarsat)
Receiving requency VHF air band: 118.000 ... 121.500 ... 122.975 MHz
VHF marine band: 156.000 ... 156.800 ... 162.025 MHz (Channel 0 ... 28, 60 ... 88, Sea+Coast)
UHF air band: 240.000 ... 243.000 ... 245.975 MHz
Cospas/Sarsat: 400.000 ... 406.025 ... 409.975 MHz
Channel pattern 25 kHz
Scanning / Monitoring mode Monitoring:
While normal operating, 4 additional frequencies will be surveilled. (Emergency frequencies 121.500; 243.000 and two free selectable frequencies)
In Standby mode the emergency frequencies, the Cospas/Sarsat and one free selectable frequency is always surveilled.
Signal Filtering Optional, all emergency frequencies can be filtered for ELT-modulation. (Disabling false alarms)
Cospas/Sarsat analysis Reception and analysis of Cospas/Sarsat data signal (112 resp. 144 bit, 400 baud, biphase L-phase modulated, with Bose-Chaudhuri-Hocquenghem error test/ specified according Cospas/Sarsat)C/S T.001 October 1999)
Indication of datacontent (mode, country, GPS-coordinates)
Bearable kinds of modulation A3E, F3E, A3X (ELT-modulation)
bearing largely independent of modulation
Polarisation Vertical
Error of polarisation = 5 at 60 field vector rotation
Garbling cone app. 30 to the vertical
Time of response = 50 ms (with sufficient receiving field strength)
Keyboard Foil on the front with integrated keyboard-matrix and EL-background illumination
TFT graphic display 320 x 240 pixel with max brightness of app. 450 cd/m, continuously variable brightness
Operating voltage 12 V ... 30 V DC
Current consumption app. 2.5 A max.
Audio External Speaker 4W (4 Ohm, 8 Ohm )
Line Out (adjustable from 100 mV pp to 2000 mV pp)
Interfaces NMEA Input/Output (RS422 and RS232)
Ethernet LAN
Testport (RS232) optional custom-specific
Alarm relay output (1 A, 30 V DC / 0.3 A, 125 V AC)
PTT input for self bearing suspression
Squelch output for external audio controlling

Mechanical Characteristics

Display Control Unit (DCU)

Weight app. 1200 g (2.7 lbs)
Tolerable operating temperature -20C ... +60C
Protection system IP 67

Antenna Unit (AU)

Weight app. 5200 g (11.7 lbs)
Tolerable operating temperature -40C ... +60C
Protection system IP 67
Search and Rescue (SAR)
Manpack Search and Rescue
RHOTHETA DF systems can also be installed on land vehicles. Furthermore, there are manpack systems available which allow for carrying the system where it is impossible to go by car.

Our Suitable products:


RT-500-M Manpack
SAR DF System