The RT-500-M operates between 118 and 470 MHz, including COSPAS-SARSAT (CP-SS) and all other V-UHF international distress frequencies. MOB-functionality for crew safety is a standard feature. Extended V-UHF air bands support cooperation with civil and military airborne forces, and the extended UHF FM band covers LMR, PMR and LPD radio frequencies, often used by smugglers and pirates. Scan functions allow creating a scan list, scan all 19 CP-SS channels, or scan multiple SAR frequencies sequentially (CP-SS…121.5…243.0). Additionally it decodes CP-SS data from an emergency beacon and thereby displays the beacon’s ID, its latitude-longitude location, as well as direction and distance to the beacon.

The RT-500-M calculates the bearing to an incoming radio signal with an accuracy of 5° RMS. Standard serial, NMEA, and Ethernet interfaces allow integration with ECDIS systems, sharing DF bearing and location data in real time. The installation of the light weight compact antenna (AU) system requires no RF cables. A distance of 100 m between AU and Display Control Unit (DCU) is no problem.

The RT-500-M direction finding system is ideal for SAR, Coast Guard, and Law Enforcement organizations, easy to install on any size of vessel and practically maintenance free.

All features at glance

• Wide-band radio direction finder‚ 118 to 470 MHz

• Numerous scan functions (COSPAS-SARSAT-Scan, SAR-Scan, Creation of scan lists, Creation of frequency exclude lists, Automatic creation of hit lists)

• MOB function: Saves the current position when pressing the MOB button and then displays the direction and distance to that position.

• High reception sensitivity to permit detection of extremely weak and distant signals

• Designed for use under very rough conditions at sea (IP 67 protection)

• Easy installation, no RF cables required

• Compact wide-band antenna system (Patent DE 4421759 C1)

• 3x NMEA, RS-422 and RS-232 interfaces for system integration and remote control

• DF of all 19 COSPAS-SARSAT channels

• Decode of COSPAS-SARSAT messages

• Storage of several COSPAS-SARSAT messages

• Shows direction and distance to GPS-position of COSPAS-SARSAT beacons

• VHF Air band in 8.33 kHz steps available

• UHF band including frequencies of SRD/LPD and PMR devices (used by pirates and smugglers)

Technical Data

Method of bearing

Doppler-principle (3 kHz rotational frequency)

Bearing Indication

Relative bearing and True/ Magnetic bearing (if ext. heading data available)

Bearing accuracy

≤ 5° (RMS)


Frequency stability

±2.0 ppm

Basic Frequency range

VHF air band: 118.000 to 124.000 MHz
VHF marine band: 154.000 to 163.000 MHz (Channel 0 to 88, Sea & Coast)
UHF air band: 240.000 to 246.000 MHz
Cospas/Sarsat: 400.000 to 406.092 MHz
UHF-FM Band: 406.100 to 410,000MHz

Frequency extensions possible see below in Accessories

Frequency Options

F1 VHF-Airband: 118.000 – 136.992 MHz
F2 VHF-Marineband: 137.000 – 224.995 MHz
F3 UHF-Airband: 225.000 – 399.975 MHz
F4 UHF-FM Band: 406.100 – 470.000 MHz

Channel spacig

VHF Air Band: 8.33 kHz
VHF Marine Band: 5/25 kHz
UHF Air Band: 25 kHz
UHF FM-Band: 5 kHz

Scanning / Monitoring mode

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.

Selectiv Squelch

Trigges an alarm only if a emergency signal is detected. (to avoid fails 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 modulation types

A3E, F3E, A3X (ELT-modulation)
bearing largely independent of modulation



Error of polarisation

≤ 5° at 60° field vector rotation

Time of response

≤ 50 ms typ. (with sufficient receiving field strength)


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/m², continuously variable brightness

Operating voltage

12 V to 30 V DC

Rated current

2.5 A


External Speaker 4W (4 Ohm, 8 Ohm )
Line Out (adjustable from 100 mVpp to 2000 mVpp)

Data Interfaces

NMEA IBus (RS422 and RS232)
Secondary DCU (RJ-45)


DCU: app. 1200 g (2.7 lbs)
AU: app. 5200 g (11.7 lbs)

Operating temperature

DCU: -20°C to +60°C
AU: -40°C to +60°C

Ingress Protection

IP 67

Bearing sensitivity VHF Airband

≤ 4 µV/m / 2,5 µV/m typical at ±5° bearing fluctuation

Bearing sensitivity VHF Marineband

≤ 3 µV/m / 2 µV/m typical at ±5° bearing fluctuation

Bearing sensitivity UHF Airband

≤ 6 µV/m / 4 µV/m typical at ±5° bearing fluctuation

Bearing sensitivity COSPAS-SARSAT

≤ 6 µV/m / 4 µV/m typical at ±5° bearing fluctuation

Bearing sensitivity UHF FM-Band

≤ 6 µV/m / 4 µV/m typical at ±5° bearing fluctuation


Optional Frequency extensions

Full width rt 500 m frequenz option

F1 VHF-Airband: 118.000 – 136.992 MHz
F2 VHF-Marineband: 137.000 – 224.995 MHz
F3 UHF-Airband: 225.000 – 399.975 MHz
F4 UHF-FM Band: 406.100 – 470.000 MHz

The Optional Frequency extensions can be ordered seperatly to extend the frequency range of each system individually.

DC/DC Converter

Full width dcdc 24 v hp ready

The DC/DC converter prevents damage to the direction finding system due to voltage spikes generated when starting the engines.

Antenna Measurement Device

Full width rt 500 m tester frei

The ram tester offers every integrator / installer the ideal tool to check the function of the RT-500-M direction finder.

Optional channel scan function F5

Full width rt 500 m scan modus frei

Extension F5 add´s a fast channel scan (within a maximum of 2 sec) to the device. Up to eight freely selectable frequencies / channels can be programmed in one scan cycle.


Search and Rescue (SAR)

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Monitoring Communication

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DGzRS Deutsche Seenotretter

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Canadian Coast Guard

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Nederlands Loodswezen B.V.

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US Coast Guard

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