Vibration resistant industrial radios

An introduction to the VX2M (and other low microphony modules)


Radiometrix manufactures an impressive range of high performance multichannel narrowband modules, in a family led by the TR2M transceiver. However, these designs are based around a conventional low noise integer-N PLL frequency synthesizer, and this class of circuits are prone to microphony (sensitivity to mechanical vibration), which can make them unsutiable for use in some hostile heavy industrial environments
The VX2M is the solution to this problem. Using alternative circuit architechtures, it delivers a UHF (400MHz band) module with exceptional vibration resistance while otherwise exactly matching the performance, frequency range, footprint and pin-out of the popular TR2M

Key features

Narrow Band (for use where existing wideband modules lack the necessary range or robustness)

Highly resistant to mechanical vibration. Very low microphony
True Multi-channel (parallel select, or up to 128 channels by serial command)
Excellent RF specifications. Diode ring mixer for good large signal RX performance
Identical to TR2M family footprint (59mm x 38mm), pin-out and interfaces
Re-programmable via RS232. Can be ordered on a wide range of frequencies in the 400MHz band
Range of 1km and above (100mW TX output power)
Conform to EN 300 220-2 (full category one compliance) and EN 301 489-3


The VX2M is a high performance (400MHz UHF) narrowband multichannel transceiver module. It is a true drop-in replacement for the conventional TR2M, while also providing a greatly increased resistance to vibration (without compromising RF performance) by virtue of it's unconventional multiple-loop PLL frequency synthesizer.
Features include:
logic level and variable gain AF modulation inputs
inverted and non-inverted modulation polarity versions
transmit output power up to 100mW (+20dBm)
raw audio and squared (digital logic) baseband outputs
selectable noise squelch (mute) on the AF output
wide dynamic range analogue RSSI output
parallel or serial channel frequency selection.
Identical interface and programming commands to TR2M

And more
To simplify implementing a wireless solution based on this modules, the VX2M firmware includes exactly the same simple (but effective) radio modem sub-system as used by the TR2M transceiver, which can similarly 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 and is fully compatible with all other Radiometrix modules equipped with “i1200 modem” functionality (including TR2M, TX2M, RX2M, SMX2, USX2 and others), and with the i1200/NBEK chip.


This radio is intended for the most physically demanding of industrial applications, where both a hostile RF environment challenges radio performance, and significant amounts of mechanical vibration prevent the use of the existing more “conventional” multichannel radios in the TR2M (and RX2M / TX2M) families.
Applications include monitoring equipment mounted on heavy industrial machines, earth moving equipment and all terrain vehicles, as well as situations where the radio is mounted in close proximity to pumps, diesel generators, machine tools or drilling rigs.

Beyond the basic family

While the VX2M is a highly capable unit, there have recently been several other units added to the Radiometrix product range that provide similar vibration resistant performance.

The adaptable LM_ family now includes vibration resistant transmitters at 10mW (LMT2B and 100mW (LMT2C) power levels, and a vibration resistant receiver (LMR2B) with better-than category two performance nearly matching the VX2M

The 400MHz band TX2MG transmitter detailed in the TX2M (etc) family also exhibits (as a consequence of it's fractional N (sigma delta) frequency source) a greatly enhanced resistance to mechanical vibration (microphony), and can be considered the transmitter (TX2M pinout) complement to the VX2M transceiver

It should also be noted that, while not quite in the same (top end of category one) performance bracket as the VX2M, both the narrowband and wideband single frequency SIL and BiM modules also have a similarly high degree of vibration resistance, and should be considered where ultimate category one performance, or the highly versatile interfaces of the VX2M, is not strictly needed.

Evaluation & Application Boards

Any of the application boards intended for the TR2M (or SFX2) can be used with the VX2M.
These boards include an application board hosting the M48 modem chip and a (VX2M) transceiver, and a number of industrial control boards using the CTA88 chip, and variants of it
For test and evaluation purposes, the VX2M can use the same “TR2M pin-out” carrier board with the NBEK test motherboard, as with the other members of the “high performance multichannel” family