NDB Transmitters

The NDB Transmitters (JTM-30C and JTM-50C) are available as Single and Dual Transmitters. As Dual Transmitter they have two complete transmit chains with fault detection/reporting and automatic changeover.
The JTM-30C and JTM-50C versions are built upon on a totally new concept for NDB transmitters utilizing digital Exciters and PC controls. The transmitters have, among other facilities, following main features:
  • The carrier frequency may be set in steps of 1 Hz from 190 kHz to 2MHz
  • Frequency generation by Direct Digital Synthesis featuring high linearity and stability of carrier and modulation, low noise and excellent frequency accuracy
  • The Exciter provides full power control of the carrier
  • The transmitters operate with N0N/A2A or N0N/A3A emission.
  • MSK modulation available as an option
  • A Timer function enables four different Morse sequences:
  • Continuous transmission of Morse keying, with automatic keying sequence repetition
  • Transmit one time Morse keying sequence only
  • Transmit repeated Morse keying sequences during a specified interval
  • Transmit the Morse keying sequence once for every specified interval
  • All versions of transmitters are equipped with functions for monitoring the transmitter in operation, carrier level, modulation and failure conditions
  • Flexible control and monitoring from an attached PC via RS485, or from any remotely connected Internet PC via locally dedicated NDB PC
  • Through the RS-485 remote control interface all parameters above may be monitored and/or controlled
  • The RS-485 remote control interface also provides an event log that records all system events, such as restart, parameter changes and error events
  • The NDB Transmitters have built-in non-volatile memory sufficient for storage of the entire transmitter configuration enabling stand-alone un-attended operation. Saving the configuration in solid-state memory is controlled via the PC interface
  • In addition to the PC interface, the NDB Transmitters also include Remote Control Unit interface that can be attached via a separate galvanic isolated port to provide simple operation of the transmitter from remote location(s). The Remote Control Units may be chained to more than one location up to 500 m between Transmitter and Remote Control(s)
JTM-30C may be delivered with 100W RF power output power from the RF Amplifier or 250 WPEP.
JTM-50C may be delivered with 500W RF power output power from the RF Amplifier or 1000 WPEP.


The NDB Transmitters TS-1B is a Single Transmitters..
This is a low cost "old-timer" delivered since 1984. Many of the early delivered transmitters from 1980s are in daily operation. The transmitters have following main features:
  • Frequency range from 190 to 1250 kHz
  • Frequency generated by crystal
  • Programming of ship/Rig call sign (Morse) is inside a PROM
  • The transmitters operate on emission N0N/A2A
  • A Timer function enables four different Morse sequences:
  • Continuous transmission of Morse keying, with automatic keying sequence repetition
  • Transmit one time Morse keying sequence only (typical 35 minutes)
  • Operation from nominal 24VDC or 48VDC
  • Power output from RF Amplifier is 100W PEP (48V operation) and 50W PEP (24V operation)