UHF Narrow Band FM Multi channel Transceiver

The TR2M transceiver module offers a low power, reliable data link in an industry-standard pin out and footprint. This makes the TR2M ideally suited to those low power applications where existing wideband modules have insufficient range, or where multi-channel operation is needed. Two versions are available, covering the 458.5-459.1MHz UK band (at 100mW) and the European 433.05-434.79MHz band (at 10mW).


  • 433MHz version conforms to EN 300 220-3 and EN 301 489-3 and 458MHz version to MPT 1329 UK specs.
  • Any 5MHz band module from 420MHz to 480MHz available as factory tuned custom variant
  • High performance double superhet, 128 channel PLL synthesizer with TCXO
  • Data rates up to 5 kbps for standard module
  • Usable range over 1km (with 100mW variant)
  • Fully screened
  • Feature-rich interface (RSSI, noise squelch, analogue and digital baseband)
  • Incorporates a 1200baud dumb modem
  • Re-programmable via RS232 interface
  • Low power requirements


  • Handheld terminals
  • Heavy vehicle/machine remote controls
  • EPOS equipment, barcode scanners
  • Data loggers
  • Industrial telemetry and telecommand
  • In-building environmental monitoring and control
  • High-end security and fire alarms
  • Vehicle data up/download

Technical Summary

  • Operating frequency: 458.5-459.1MHz or 433.05-434.79MHz
  • Custom variants from 420MHz to 480MHz on any 5MHz band
  • 23 channels in 458MHz band, 69 channels in 433MHz band (128 channels max.)
  • Transmit power: +20dBm (100mW) nominal
  • Supply range: 4.5V - 16V
  • Current consumption: 110mA transmit, 27mA receive
  • Data bit rate: 5kbps max. (standard module)
  • Receiver sensitivity: -118dBm (for 12 dB SINAD)
  • Size: 59 x 38 x 10mm

Evaluation Platform: Narrow Band Evaluation Kit

Figure2: TR2M block diagram

Figure 3: TR2M Footprint (Top)

Pin Description - TR2M

Pin Name Function
Power: A
1 Vcc +4.5V to 16V supply
2 Gnd Ground
1 RF Gnd RF ground
2 RF To the antenna
3 RF Gnd RF ground
User: C
1 TXE (MOD TX_ON) Transmitter enable. Low = ON, open = RX mode. Internal 10kW pullup to 4V
2 TXD (MOD NC) DC coupled digital data input for 3-12V CMOS logic. Leave open if unused
3 AF in (MOD NC) AC coupled Analogue Input Limit to 1Vpk-pk ±10% to keep distortion <1.5% and peak deviation >2.5kHz
4 RSSI DC level between 0.5V and 2.5V. 60dB dynamic range
5 SQF (MOD NC) Noise operated carrier detect. Open collector. ON/low = no signal
6 AF out 200mVpk-pk audio. DC coupled, approx 1V bias. Muted by squelch
7 RXD (MOD NC) Open collector output of data slicer suitable for biphase codes
8 +4.4Vout Regulated DC supply. 75mA max. drain. Present if unit is powered
9 0V Ground
10 PGM Serial programming/control input at true RS232 level
11 P1 (MOD TXD) Parallel frequency select inputs. Inverted logic, 10k pullups to 4V
12 P2 (MOD RXD)
13 P3 (MOD NC

1. TR2M receiver section inverts the sense of the baseband stream, so a logical inversion is present between input of TX and output of RX. A version is available (TR2I) which inverts the transmit datastream as well (resulting in no net inversions between a pair of TR2I radios).
2. Carrier detect on TR2M mutes the AF and RXD outputs. It can be factory disabled.
3. All the open collector outputs must be connected to Vcc/+4.4V out via a pull-up resistor.
4. The software incorporates a 1200baud dumb modem, compatible with that implemented in TX2M, RX2M radios (i1200 tones and format)
5. With 1200baud modem mode enabled, parallel selection of channel is unavailable as the P1-P3 lines are used for input/output operations.
6.PGM and MOD TXD (pin 10 and 11) tolerate true ±RS232 levels. No buffering is required.

Figure 4: TR2M interfaced to host microcontroller and serial port for configuration

TR2M can be directly interfaced to a host microcontroller which can generally be powered by the regulated +4.4V output on pin 8 of TR2M. Three I/O pins on the microcontroller port can be assigned to select the first 8 channels on frequency table of the appropriate band for which the module is configured by pulling the P1-P3 pins low. Channel select pins of TR2M have internal pull-up to 4V supply rail, hence channel selection operate on inverted logic.

Channel P3:P2:P1 433MHz band 458MHz band
0 111 433.050 458.525
1 110 433.075 458.550
2 101 433.100 458.575
3 100 433.125 458.600
4 011 433.150 458.625
5 010 433.175 458.650
6 001 433.200 458.675
7 000 433.225 458.700

Digital Received Data Output (RXD) pin is an open collector output, which should be pulled-up to required voltage swing level (e.g. +4.4V or Vcc).
TR2M has an automatic noise squelching function which is activated when there is not any RF signal at detectable level on the channel or if the non-coherent noise like interference level is high enough to block any weak RF signal from being received. SQF is provided as an open-collector output for monitoring which should be pulled-up to required voltage swing level. SQF output will jump to pull-up voltage level if received RF signal level at the RF In/Out pin of the module is about 3dB below the level required to produce 12dB SINAD level on demodulated AF Output signal. SQF pin can be connected to an LED to act as a Carrier Detect indicator. Pull-up resistor value should be reduced (e.g. 1kW) according to the current requirement to produce satisfactory brightness on the LED used.

TR2M can be configured using any PC/Laptop/PDA having a serial port and modem/terminal program. TXD (pin 3) of DB9M connector can be directly wired to PGM (pin C10) of the TR2M and SGN (pin 5) of DB9M connector should be either connected to common ground or pin C9 of the TR2M.

The whole frequency/channel table is user reconfigurable to 128 channels within 5MHz band of supplied frequency subject to regulatory band limits. Serial Channel Selection via PGM pin gives access to the whole of regulatory band allocation for 433.05MHz-434.790MHz (69 channels) or 458.525MHz-458.925MHz (23 channels).

Received Signal Strength

Figure 5: RSSI voltage variation with respect to RF level at TR2M

If the microcontroller has a built-in Analogue to Digital Converter (ADC), the Received Signal Strength Indicator (RSSI) output voltage level can be read by the microcontroller to estimate its distance from transmitting TR2M unit or identify areas of weak signal reception.
RSSI can also be used to make a decision to switch to the second antenna in fixed installations within building where the probability of null-spots are higher.

Regulatory Restrictions

There is a generic 10% duty cycle restriction on the 433MHz ISM band through out European countries with few exceptions. Annex 1 Band E, Band E2 of European Radio Communications Committee (ERC) Recommendation 70-03 dated February 2004 specifies the following:

433.050MHz (Ch0)
434.050MHz (Ch40)
433.775MHz (Ch69)
10mW ERP, 10% duty cycle for Channelised Narrow Band and Wide Band usage
10mW ERP, 100% duty cyclefor <25kHz Channelised Narrow Band usage

433.050-434.790 MHz, Non Specific Short Range Device, band is primarily intended for Telemetry, Telecommand, Alarms, Data in general and other similar applications. Audio and Voice signals should be avoided in the band.

TR2M serial interface commands

SINGLE nnnnn set value of N for single channel operation
GOCHAN xx serial select of channel xx (0 to 127)
LOADMX xx set highest permitted (serial selected) channel xx (others default to ch0)
LOAD aa nnnnn set value of N for channel aa (channels 0 to 15)
LOADTB nnnnn set value of N for channel 16 (channels 17 to 127 then in sequence)
RVALUE rrrr enter value for R register
SETPAR channel selected by 3 bit parallel input (0 to 7). Disable modem
SETSER channel selected by most recent 'gochan' operation
SETMOD enable internal modem. Frequency selected by most recent 'gochan' or 'single'
GOTEST 250Hz test tone transmission
OFFSET ooo Set receive frequency offset (for 25KHz this is 1800)
<cr> process entry
/ clear all buffer

xx = a channel number from 00 to 127
aa = a two digit channel number from 00 to 15
nnnnn = a synthesizer N register value, (up to 65535)
rrrr = the synthesizer R register value, (up to 16383)
000 = frequency offset

, So R = 520

RX OFFSET = IF/Channel spcacing 45MHz /25kHz = 1800

Channel number 433MHz band N value for TX 458MHz band N value for TX
433.050 /LOAD00 17322 458.525 /LOAD00 18341
433.075 /LOAD01 17323 458.550 /LOAD01 18342
433.100 /LOAD02 17324 458.575 /LOAD02 18343
433.125 /LOAD03 17325 458.600 /LOAD03 18344
433.150 /LOAD04 17326 458.625 /LOAD04 18345
733.175 /LOAD05 17327 458.650 /LOAD05 18346
433.200 /LOAD06 17328 458.675 /LOAD06 18347
433.225 /LOAD07 17329 458.700 /LOAD07 18348
433.250 /LOAD08 17330 458.725 /LOAD08 18349
433.275 /LOAD09 17331 458.750 /LOAD09 18350
433.300 /LOAD10 17332 458.775 /LOAD10 18351
433.325 /LOAD11 17333 458.800 /LOAD11 18352
433.350 /LOAD12 17334 458.825 /LOAD12 18353
433.375 /LOAD13 17335 458.850 /LOAD13 18354
433.400 /LOAD14 17336 458.875 /LOAD14 18355
433.425 /LOAD15 17337 458.900 /LOAD15 18356
433.450 /LOADTB 17338 458.925 /LOADTB 18357
F max
434.775 /LOADMX 69 459.100 /LOADMX 23

Figure 6: Maximum regulatory and user accessible sequential channels

Figure 7: TR2M serial configuration using HyperTerminal

1. A pause of at least 50ms must be allowed between command strings (EEPROM programming time) SINGLE mode does not store the N value in EEPROM. Therefore the unit is inoperative after a power down until either another valid SINGLE command is received, or mode is changed by a GOCHAN, SETPAR or SETSER command. SINGLE mode is intended for frequency agile applications.
2. /SETPAR command should be issued at the end of channel programming to put the module back into parallel frequency select mode
3. In 458MHz band, channel 12 (458.825MHz) and channel 15 (458.900MHz) are allocated specifically for fixed alarm and radio keys/vehicle paging applications respectively and should not be used for general purpose applications.
4. User can modify the frequency table of 128 channels to any desired frequency by changing N, R values of synthesizer within ±2.5MHz of factory set Channel 0 frequency subject to the Radio Regulatory Band Allocation in the country of intended use.
5. All other frequency, power, analogue input gain and automatic noise squelching adjustment will be treated as custom variants of the module to be set by factory.

Pin description of TR2M with Modem mode selected

The 'modem' mentioned is a 1200 baud RS232 semi-intelligent unit (Transmit keyed when valid serial data is present, so no separate TX control needed. Coding in the datastream also permits the receiver to ignore noise and only output valid serial data). This is a half duplex unit, so collisions between transmitted and received packets must be dealt with by the user.

Pin Description - TR2M

1 MOD TX_ON Open = normal modem operation. Low = constant TX (for test) 10k pullup to 4V
2 MOD NC Leave open
3 MOD NC Leave open
4 RSSI DC level between 0.5V and 2.5V. 60dB dynamic range (only valid during databursts)
5 MOD NC Leave open
6 AF out Modem tones or noise present
7 n/c Leave open
8 +4.4Vout Regulated DC supply. 75mA max. drain. Present when unit is powered
9 0V Ground
10 PGM Serial programming/control input at RS232 level
11 MOD TXD RS232 data input (true). 10k pullup to 4V
12 MOD RXD Inverted "RS232" data out (to inverting buffer like MAX232)
13 MOD NC Leave o

TR2Ms on both ends should be configured to required operating frequency using GOCHAN command before starting to use the internal 1200 baud modem, because the P1-P3 pins will be used as Modem Data pins and the modem will operate on the last serially selected channel after SETMOD command is used to enable the Modem.

Figure 8: TR2M interfaced to PC serial port in modem mode

Note: Baud rate used for Modem is half that of used for serial configuration. Attached RS232 devices should be set with the following:
1200bps, 8 Data bits, No Parity, 1/2 stop bits, no flow control

TXD (Pin 3) of a Serial Port can be switched from PGM (Pin C10) to MOD TXD (Pin C11) with no RS232 driver in between. However, MOD RXD (Pin C12) requires an RS232 line driver before it can be connected to RXD (pin 2) of a serial port. Some of the RS232 line drivers can be powered from the regulated +4.4V out (Pin C8).

Condensed specifications

Frequency 458.5-459.1MHz or 433-434MHz (or any 3MHz band from 420-475MHz)

Frequency stability

+/- 1.5kHz
Channel spacing
25kHz (12.5kHz by special order)
Number of channels
128 channels controlled via RS232 interface (8 parallel selected)
Supply       voltage 4.5V - 16V
Current 110mA nominal transmit
27mA receive
Operating temperature -10 to +60 °C (Storage -30 to +70 °C)
Size 59 x 38 x 12mm
Spurious radiations Compliant with ETSI EN 300 220-3 and EN 301 489-3
Interface      user 13pin 0.1" pitch molex


2pin 0.1" pitch molex


3pin 0.1" pitch molex
Recommended PCB hole size 1.2mm
Intended approval ETSI radio standard EN 300 220-3 and EMC standard EN 301 489-3
Output power 100mW +/- 1dB (factory adjustable 1 - 100mW)
TX on switching time 50 ms
Modulation type FM, FSK (F1D, F3D)
TX modulation bandwidth DC - 3kHz
Adjacent channel TX power <-37dBm (<200nW)
TX spurii better than -40dBm
Inputs analogue, data (CMOS/TTL compatible)
Sensitivity -118dBm for 12 dB SINAD
adjacent Channel 65dB
-910kHz 69dB
1/2 IF >80dB
image >80dB
blocking 86dB
outputs RSSI, carrier detect, audio, data
Power on to valid audio (no noise mute) 28ms
Power on to valid audio (with noise mute ) 45ms
Power on to stable data out (50:50 mark / space) 50ms (with or without mute


  1. The data slicer cannot be depended upon for data waveform frequencies below 250Hz
  2. When RX is on and a transmitter keys up, again a 50ms period is required to stabilise data output mark/space. i.e. allow at least 50ms of preamble

Transceiver Variants

TR2M is designed to be pin and polarity compatible with existing industry standard modules. Analogue and Digital Data Output are inverted relative to original transmitted signal in Receive Mode.

The transceiver is available in two variants - TR2I and TR2M

TR2M, in Transmit Mode, frequency modulates the carrier frequency in the normal sense whereby higher modulating voltage increases the carrier frequency and lower modulating voltage decreases the carrier frequency which results in an inverted Analogue and Digital Data output on the TR2M in Receive Mode. This will be the standard module and exact plug-in replacement for existing industry standard modules.

Figure 9: Data polarity change from TR2M (in transmit mode) to TR2M (in receive mode)

TR2I, in Transmit Mode, reverses the Frequency Modulating order whereby the higher modulating voltage decreases the carrier frequency and lower modulating voltage increases carrier frequency which results in non-inverting Analogue and Digital Data output on the receiver. This variant can be used for applications where data inversion will be problematic.

Figure 10: Data polarity change from TR2I (in transmit mode) to TR2I (in receive mode)

Ordering information

Part Number Description Frequency band Data rate (max)
TR2M-433-5 TX2M transceiver (inverting receiver) 433.05MHz-434.790MHz 5kbps
TR2I-433-5 TX2I transceiver (inverting transmitter & receiver) 433.05MHz-434.790MHz 5kbps
TR2M-458-5 TX2M transceiver (inverting receiver) 458.525MHz-459.100MHz 5kbps
TR2I-458-5 TX2I transceiver (inverting transmitter & receiver) 458.525MHz-459.100MHz 5kbps
TR2M-458-10 TX2M transceiver (inverting receiver) 458.525MHz-459.100MHz 10kbps
TR2I-458-10 TX2I transceiver (inverting transmitter & receiver) 458.525MHz-459.100MHz 10kbps

Limitation of liability

The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd reserves the right to make changes or improvements in the design, specification or manufacture of its subassembly products without notice. Radiometrix Ltd does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. This data sheet neither states nor implies warranty of any kind, including fitness for any particular application. These radio devices may be subject to radio interference and may not function as intended if interference is present. We do NOT recommend their use for life critical applications.
The Intrastat commodity code for all our modules is: 8542 6000.

R&TTE Directive

After 7 April 2001 the manufacturer can only place finished product on the market under the provisions of the R&TTE Directive. Equipment within the scope of the R&TTE Directive may demonstrate compliance to the essential requirements specified in Article 3 of the Directive, as appropriate to the particular equipment.
Further details are available on The Office of Communications (Ofcom) web site:
Licensing policy manual