MTX2: UHF Narrow Band FM sub-miniature transmitter

Radiometrix has introduced a range of RF transmitters which it is offering as small-format alternatives to 12.5kHz/25kHz narrowband FM transmitters.

The MTX1, MTX2, and MTX3 are four-channel transmitters operating on 120MHz-180MHz; 420MHz-470MHz; and 850MHz-950MHz respectively. They measure 23×12.5x7mm. Their transmit power is +10dBm, which the supplier says will allow for a typical usable range of up to 500m as long as you use a matching narrowband receiver.

The transmitter’s conformance to EN 300 220-2 (radio) and EN 301 489-3 (EMC) standards will meet regulatory requirements for license exempt short-range devices. With built-in shielding, each module contains the transmitter IC and baseband circuitry, plus user-accessible digital and analogue inputs, which enables even analogue signals like AFSK, GMSK and DTMF tones to be transmitted. A 3V voltage regulator and brown-out reset controller are onboard.

Programming is via a simple RS-232 serial interface. The input voltage range of 3.1V to 15V helps to simplify system design, while energy-conscious performance (drawing typically 20mA) maximises the life of battery-powered applications

Data Sheet

The MTX2 transmitter module adds a totally new subminiature form factor to the existing range of Radiometrix ISM band devices. Using cutting edge integrated RF devices, it offers multi channel, low power narrowband operation in a previously unobtainable size. It is ideally suited to applications where existing wideband modules have insufficient range and where traditional narrowband modules would physically be too big to fit in.


  • Conforms to EN 300 220-2 and EN 301 489-3
  • High performance Fractional N (Sigma-Delta) Synthesizer with TCXO
  • Vibration resistant (negligible microphony)
  • Data rates up to 10 kbps for standard module
  • Usable range over 500m (with suitable aerials and matching receiver)
  • Fully screened. Very low profile
  • Feature-rich interface (analogue and digital baseband)
  • Re-programmable via RS232 interface
  • Low power requirements


  • Keyfobs and other hand held terminals
  • Small form factor data loggers
  • Industrial telemetry and telecommand
  • In-building environmental monitoring and control
  • Covert, high-end security devices
  • Unobtrusive fire alarm sensors
  • Heavy vehicle/machinery controls

Technical Summary

  • Operating frequency: 433.875-434.650MHz (EU band)
  • 458.525 – 459.1MHz (UK band)
  • Other custom UHF bands
  • 850-950MHz version (MTX3) also available
  • 4 parallel channels (also fully controllable via serial port)
  • Transmit power: +10dBm (10mW)
  • Supply range: 3.1 – 15V (will operate down to 2.9V)
  • Current consumption: 20mA @ 10mW
  • Data bit rate: 10kbps max. (standard module)
  • Serial configuration by inverted RS232 at 3V CMOS level
  • Size: 23 x 12.5 x 7 mm

Evaluation platforms: NBEK + matching carrier board

Radiometrix launches compact long range transmitter

Radiometrix has launched a new, highly compact transmitter module with a range of typically over 5km when paired with a suitable receiver. The new HMT2 transmitter is a multi-channel, narrowband design, suitable for use in many high power licensed and unlicensed UHF allocations worldwide.
Within a compact 66 x 23 x 9 mm package, the new Radiometrix HMT2 transmitter module offers a 500mW RF output in the UK 458MHz and the Danish /German 433MHz bands. The operating channel frequency is pin selectable – the HMT2 offers 16 parallel and 32 serial channels at frequencies between 458.525 – 459.1MHz. The module draws just 350mA in transmit mode, less than 5µA on standby. It offers a data rate of 5kbps and a DC-3kHz analogue interface for the standard module. The HMT2 module is fully shielded, enjoying high immunity to external interference, and conforms to ETSI EN 300 220-2 (radio) and EN 301 489-3 (EMC) standards. The HMT2 is a PLL synthesised transmitter clocked by a VCTCXO.

With its compact size and low power consumption, the HMT2 is ideal for battery powered applications like hand held terminals, on-site paging systems, lone worker alarm, security and fire alarms. Radiometrix also anticipates that the long range of the module will make it popular for data loggers, industrial telemetry and remote control systems and for vehicle data upload / download.

When used with a matching LMR2 receiver a one-way radio data link can be easily set up to achieve a distance of typically 5km (with a suitable antenna).

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