Direction Finders
Locator Beacons
Emergency Receivers
4-Band VTS Radio Direction Finder


Vessel Traffic Service (VTS)

The RT-800 is a radio direction finder for stationary coast surveillance and identification of ships that are transmitting on the VHF radio band. The bearing information from transmitters can be correlated with the corresponding radar target and AIS-position information at a VTS (Vessel Traffic Service) centre. Two or more RT-800 Systems on different locations can be used to locate a ship’s exact position by triangulation. The RT-800 can easily be integrated in a VTS environment.

The RT-800 operates on four frequency bands:

  • All 19 Cospas-Sarsat frequencies between 406.022 and 410.000 MHz
  • Marine VHF from 156.000 MHz to 162.025 MHz including channel 16
  • Civil VHF air band from 118.000 MHz to 123.999 MHz, including the international emergency frequency of 121.500 MHz
  • Military air band from 240.000 MHz to 245.975 MHz including the military emergency frequency of 243.000 MHz

Special Features

  • Best relation of performance and price
  • Decoding of transmissions on all 19 Cospas-Sarsat channels
  • Bearing (finding the direction) of the Cospas Sarsat
  • Full manual operational functionality at installation site for calibration and service
  • Fast frequency monitoring by scanning of up to 8 frequencies
  • Low costs due to no moving parts
  • Easy and reasonable priced installation as no patched HF antenna cable has to be used
  • Effective remote operation via RS-232, Ethernet and LAN
  • Extreme compact, rugged and light-weight DF antenna for easy installation and use in maritime weather conditions
  • Maintenance-free due to no moving parts
  • External lightning protection available


Lightning protection rod

Lightning_protection The Lightning Protection Rod for precision direction finders is designed to protect direction finders from RHOTHETA against the effects of direct lightning strokes into a direction finder system.


Method of bearing Doppler-principle (3kHz rotational frequency, right/left rotation, CW/CCW)
Bearing indication Relative bearing and true bearing related to north (if external heading data available)
Bearing accuracy1 ±2° RMS
Internal resolution
Sensitivity HF-voltage at receiver input (50 Ω):
VHF, UHF < 100nV
Cospas-Sarsat 406.000 MHz < 150nV
Stability of frequency ±2.0 ppm (∆f/f = ±2 x 10-6) [in temperature range -30°C to +80°C]
Receiving bands 4 (VHF-air band, VHF-marine band, UHF-air band, Cospas-Sarsat)
Receiving frequencies (frequency ranges) VHF air band: 118.000 .. 121.500 .. 123.975 MHz
VHF marine band: 154.000 .. 156.800 .. 162.995 MHz
UHF air band: 240.000 .. 243.000 .. 245.975 MHz
Cospas-Sarsat: 400.000 .. 406.022-406.076 .. 409.975 MHz
Marine channels Channel 0 .. 28 / 60 .. 88 (ship station + coast station in each case)
Channel pattern 25 kHz / 8,33 kHz / 5 kHz (depending on frequency band)
Monitoring/Scanning modes: Monitoring:
Four additional frequencies (emergency frequency 121.500 MHz and three free selectable frequencies) are monitored during normal operation.
The Cospas-Sarsat and 121.500 MHz emergency frequency are monitored at all times in standby mode.
Fast Marine Ship Band Scan (within approx. 3sec):
Fast scan (without gap) within the range of ship channels [01..88] = [156,050 .. 157,425 MHz]. Detection of each signal (also between the channel grid).
Fast Channel Scan (within max. 2sec):
Fast scan of up to eight freely selectable frequencies/channels.
Signal filtering Optional: all emergency frequencies can be filtered for ELT-modulation (false alarms disabled).
Cospas-Sarsat analysis Reception and analysis of Cospas-Sarsat data signal (112 or 144bit, 400baud, biphase L-phase modulated, with Bose-Chaudhuri-Hocquenghem error test, specified according Cospas-Sarsat C/S T.001 October 1999)
Indication of data content (mode, country, GPS-coordinates)
Bearable modulation A3E, F3E, A2X (PLB-modulation); bearing largely independent of modulation.
Polarisation vertical
Polarisation error ≤ 5° at 60° field vector rotation
Garbling cone approx. 30° to vertical
Response time ≤ 50 ms (with sufficient reception 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 approx. 450cd/m2, continuously adjustable or automatic control.
Operating voltage 85-264 Volts / 47–63 Hz
Current consumption 1.3–0.4 A
Power consumption Nominal 30W@230V
Audio out Internal speaker 4W
Line out (adjustable from 100mV pp to 2000mV pp)
Interfaces Ethernet Interface for NMEA remote control (TCP)
Ethernet Interface for IP Audio output (e.g. Internet Radio, RTP, RawUDP, RawTCP, SIP, Icecast, Shoutcast)
External GPS (RS422, optional)
Headphone (only used for setup of IP Audio)
NMEA In/Output (RS232, only for local test purposes) Testport (RS232) optional customer specific
Alarm relay output (1.0A, 30V DC / 0.3A, 125V AC) PTT input for self-bearing suppression
Squelch output for external audio control

1 Undisturbed wave field and sufficient field strength supposed. Measuring by changing the angle of incidence, the bearing antenna rotates on a revolving table in order to eliminate influences of environment to the bearing result.