High Performance TX/RX Modules

A guide to the RX_M, TX_M and TR_M module family (& the TX3MG, TX2MG & SFX2)


This large family of common footprint and function modules from Radiometrix make up our highest performance product family, providing highly reliable radio links with full multi-channel operation at an affordable cost.

Consisting of receiver, transmitter and transceiver modules covering an exceptional range of operating frequencies, this family provides superior RF parameters for trouble free operation in hostile RF environments where a simpler module
specification may not be sufficient.

Key features

Narrow Band (where existing wideband modules lack the necessary range)
Multi-channel (parallel select, or up to 128 channels by serial command)
Excellent RF performance. Diode ring mixer for good large signal RX performance
Consistent footprint (59mm x 38mm) and low profile (TX & RX: 7mm)
Available in VHF (135 MHz - 175 MHz) and UHF (400MHz, 600MHz and 869MHz band) frequencies
Re-programmable via RS232. Can be ordered on a wide range of frequencies
Range of 1km and above
Conform to EN 300 220-3 (category one) and EN 301 489-3
Evaluation Boards available

Receivers and transmitters

The core of this family is made up of the RX1M (VHF) and RX2M (400MHz UHF) receivers, and the TX1M (VHF) and TX2M (UHF) transmitters. These are highly capable multichannel designs (using low phase noise PLL frequency synthesizers combined with high rejection crystal and ceramic channel filters) with feature rich user interfaces:
  • TX: logic level and variable gain AF modulation inputs
  • inverted and non-inverted modulation polarity versions
  • transmit output power up to 100mW (+20dBm)
  • RX: raw audio and squared (digital logic) baseband outputs
  • selectable noise squelch (mute) on the AF output
  • wide dynamic range analogue RSSI output
In addition, for a high performance receiver of it's class, the RX2M (and RX1M) have exceptionally low supply current figures (13mA from a 4.5-15v supply).


The TR1M (VHF), TR2M (400MHz UHF) and TR3M (869MHz UHF) modules add transceiver functionality to the series, with the complete functionality of both the receiver and transmitter modules in one package, in the same footprint but using an expanded (13 pin increased from 10pin) user interface connector, based on the RX2M pinout.

Receiver-only version of the transceiver (such as the 250MHz band capable TR2R and the 869MHz TR3R) are available,in instances where the user requires a frequency outside the capability of the basic RX1M and RX2M.

And more
To simplify implementing a wireless solution based on these modules, the firmware includes a simple (but effective)
radio modem sub system, which can be selected (or disabled) by a user command. In “modem” mode the module
operates as a fully transparent (half duplex) RS232 compatible data link, at 1200 baud.


This series of radios are best suited to more demanding applications in difficult RF environments such as high end industrial control and monitoring, long range radio modem applications, vehicle telematics and other high security, high integrity radio links.

Beyond the basic family

While this family already includes a wide range of functions, it has recently expanded to include some additional units: TX2MG (400MHz) and TX3MG (600 and 869MHz) transmitters. These units are functionally equivalent to the conventional TX2M transmitter but replace the conventional synthesizer frequency source with a fractional N (sigma delta) circuit, imparting a faster (25mS vs 50mS) TX on switching speed, a greatly enhanced resistance to mechanical vibration (microphony), and a higher absolute S/N ratio

 The SFX2 transceiver. Resembling the TR2M in all respects except a slightly taller (15mm) case, the SFX2 employs a more advanced “up converting” transmit strip to reduce the switching speed from 50mS to a lightning fast 5mS, and increase the transmitter output power to 500mW (+27dBm). This is the maximum allowed in the UK's 458MHz industrial band, and gives an SFX2 based link a range measured in miles.

Evaluation & Application Boards

To further simplify the implementation of user designs, a number of application/demo boards are offered, with necessary connectors and support and interface circuitry. These boards can be mounted uncased, or in some cased mounted inEAS series extrusion housings.

These boards include an application board hosting the M48 modem chip and a TR2M (or SFX2) transceiver, and a number of industrial control boards using the CTA88 chip, and variants of it.