Low Power Long Range Radio ModemSLR-434M

The SLR-434M smart modem is a compact, easy to use embedded radio modem operating in the 434 MHz ISM band. It allows conventional FSK mode communication and also communication using LoRa® mode providing long range at lower bit rate.
With high receiving sensitivity, it is possible to transmit up to a few km or more with line of sight using low RF output power.

By connecting to an external CPU or PC with UART interface, the user can send data or design simple control systems using Circuit Design's dedicated command protocol for industrial application. It is also possible to process up to 8 switching signals.

Applications include data transmission, telemetry and telecontrol.

* Under certain conditions when LoRa modulation is used in conjunction with low data rate, higher sensitivity is achieved and longer range becomes possible. When used in conventional FSK mode, up to 600 m (LOS) range should be expected.

The SLR-434M contains a Semtech's LoRa® wireless RFIC.
The LoRa® Mark and LoRa Logo are trademarks of Semtech Corporation.


  • RED compliant (EN 300 220)
  • Extremely long range operation achieved by LoRa® mode.
  • Switchable between FSK mode and LoRa® mode
  • UART interface (COM port, RS232)
  • Simple command protocol for development of user program.
  • Transmission of up to 8 switching signals using IO terminals.
  • Compact size
  • Low voltage and current consumption
  • Higher resistance to urban noise, enabling long range operation compared to conventional FSK
  • 429 MHz version available (Japan)


  • Data transmission in buildings, air conditioning control
  • Debris flow monitoring at mudslide control dams
  • River water level / dam monitoring
  • Greenhouse temperature / humidity monitoring and control
  • Sensor data transmission from underground or manhole
  • Monitoring of tunnels and bridge condition
  • Landslide warning

Other products related to this product


Embedded Radio Modem



Parameter Specification Remarks
Standard EN 300 220
Emission type F1D
RF output power < 10 mW Nominal, Contact (50 Ω), SMA
Communication method Simplex or half duplex
RF bit rate 15 to 245 bps (LoRa® mode)
4800 bps (FSK mode)
Actual speed with LoRa mode depends on spreading factor
Frequency range 433.0750 to 434.7750 MHz
Number of channels 137 Channel step 12.5 kHz
Receiver sensitivity < -133 dBm  (LoRa mode 128chip)
< -115 dBm (FSK mode)
Supply voltage 3.3 to 5.5 V 3.5 to 5.0 V recommended
Supply current 29 mA typ. (TX)
17 mA typ. (RX)
5 V
External dimensions
40 × 29 × 6.2 mm Not including the antenna connector
Modulation 2-FSK or LoRa Selectable using command
Number of I/O 8

The LoRa® Mark and LoRa Logo are trademarks of Semtech Corporation.

UART Interface

Parameter Specification Remarks
Communication method Serial communication RS232C format
Synchronization Asynchronous / UART
UART bitrate 19,200 bps
Flow control Hardware: RTS/CTS pin
Software: Xon/Xoff not used
Other parameters Data length 8 bits, no parity, 1 (or 2) stop bits

External View


DoC for CE (SLR-434M) PDF

Supplementary Information

Low power long range radio modem, SLR-434M
Demonstration video of the SLR Development Kit
Introducing the evaluation software for the low power RF modem, SLR-434M
Differences between SLR-434M (434 MHz) and SLR-429M (429 MHz) PDF


Operation Guide

Version 1.0 PDF

Test Board: TB-SLR-RS2

The TB-SLR-RS2 is an RS232 interface board for testing SLR-434M module. It can connect to the COM port of PC or PLC through the D-Sub-9 pin connector. The board is equipped with transmit, receive LED, power supply terminal, main switch and interface to sub boards. The module can be used with coax extension cable to allow optimum placement of the antenna according to the environment. Click here for more details.

This testboard does not include the modem SLR-434M. Please order if necessary.


  • Connection to PC COM port for data communication and module control
  • Using RS232 cable, extension to tens of meters possible.
  • Evaluation program available
  • Interface to sub-boards for switching operation.

External View

Board x 1
Screw x 4
Spacer x 4
Battery clip x 1

Connection to PC

For other connection methods, please refer to the TB-SLR-RS2 operation guide.

Switching Operation

Using the interface on the TB-SLR-RS2, sub boards can be attached to allow switching and loop back tests to be performed.



Note: sub boards SB-SLR-DIO-A and SB-SLR-DIO-B are required to perform the switching and loop back function and are not included. Please ensure you order them if necessary.



434 MHz

Whip antenna


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434 MHz

Outdoor Swivel Antenna


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434 MHz

434 MHz water resistant antenna with SMA connector.


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SMA - RPSMA conversion cable

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SMA - SMA conversion cable

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