10:41 09.07.2020
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+49 511 807 259-0,

433 MHz radio modem with RS-232/485 interfaces

RFU-433 is a radio modem that allows extending the RS-232/RS-485 line over the radio interface and transmitting data in the transparent mode using the 433 MHz frequency band.


  • 433 MHz frequency
  • 16 channels with channel spacing of 100 kHz
  • Radio interface baud rate, from 650 to 57600 bps
  • Transmission power - default 10 dBm, max 19 dBm
  • 1000 m transmission distance (no noise)
  • RS-232/485 line transparent extension
  • Message size of up to 512 Bytes
  • Provides Baud Rates from 1200 to 115200 bps for both the RS-232 and RS-485 interfaces
  • Electrostatic discharge protection: +/-4 kV
  • Isolation: 3000 VDC for DC-to-DC, 2500 Vrms for RS-232/485 using a photocoupler

When is it better to use RFU-433 modems?

Although, the baud rate of 433 MHz radio modems is lower than that of 2.4 GHz technology, the 433 MHz band provides the advantage of long-distance communication. Thus, this frequency is appropriate, if small amount of data is transmitted or if there is a large time interval between two long-distance transmissions, for instance, when monitoring the environmental parameters or monitoring and managing solar panels, etc.

What is the transmission distance for RFU-433 modems?

RFU-433 provides the maximum transmission distance of 500 m in the line-of-sight environment at the transmission baud rate of 9600 bps and the standard transmission power of 10 dBm. In the settings, the power can be increased up to 19 dBm, thus, increasing the distance or the transmission baud rate (so, the transmission distance can reach 1 km).

Sometimes, in order to overcome the noise that can occur in a harsh environment, the baud rate can be reduced, for instance, RFU-433 allows configuring the minimum transmission baud rate of 650 bps.

How to configure RFU-433 modem?

To adjust the required radio frequency channel, the transmission power and the time interval, use a special utility program when connected to a COM port of a device.

Selecting baud rate of COM ports and radio interfaces, data formats, group IDs, as well as operation modes is performed using the Rotary and DIP switches, thereby providing easy system maintenance if RFU-433 modem needs to be replaced.

What are the radio frequency channels and group IDs configured for?

Radio frequency channels and group IDs can be configured, in order to avoid interferences that occur when two RFU-433 networks work nearby. 16 radio frequency channels and 8 group IDs can be set up to separate and manage various 433 MHz networks.

Usage examples:

Fig. 1 One -to-One transmission

Fig. 2 One-to-Many transmission

Fig. 3 Repeater mode
10:41 09.07.2020