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

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