RFD900 Radio Modem

AVAILABLE NOW at :  RFDesign Online Store (Australia ) ; JDrones ( Thailand ) ; Bask Industries (Australia) ; Event 38 (USA) ; Goodluckbuy (China)

The RFD900 is a high performance 900MHz, ISM band radio modem covering the 902 - 928 MHz frequency band.  It is designed for long range serial communications applications requiring best in class radio link performance.  

New software features include multi point capability to allow for networks of RFD900 modems.


 Key Features:

  • Long range >40km depending on antennas and GCS setup
  • 2 x RP-SMA RF connectors, diversity switched.
  • 1 Watt (+30dBm) transmit power.
  • Transmit low pass filter.
  • > 20dB Low noise amplifier.
  • RX SAW filter.
  • Passive front end band pass filter.
  • Open source firmware (V1.x) / tools, field upgradeable, easy to configure.
  • Small, light weight.
  • Compatible with 3DR / Hope-RF radio modules.
  • License free use in Australia, Canada, USA, NZ.


  • RF : 2 x RP-SMA antenna connectors - it is OK to have only one antenna connected
  • Serial: Logic level RS232 (+3.3v nominal, +5v tolerant)
  • Power: +5v, ~800mA max peak (at maximum transmit power)
  • GPIO: 6 General purpose IO (Digital, ADC, PWM capable). 


16 way connector pinout

 9 way test pad pinout

Physical pinout

The following cable from FTDI is compatible with the RFD900 modem. Pin 1 of the FTDI cable connects to Pin 1 of the RFD900 header.
To power the modem from the +5V USB power, a jumper is needed between pins 4 and 6. 
To power the modem from an external +5V supply, connect power to pins 2 and 4 as shown above. 
To force the modem into boot mode, short circuit pads 1 and 2 (labeled BOOT) on the 9 way test pads.


  • Frequency Range:  902 - 928 MHz (USA) / 915 - 928 MHz (Australia)
  • Output Power: 1W (+30dBm), controllable in 1dB steps ( +/- 1dB @ <20dBm, +/- 0.5dB >=20dBm typical )
  • Air Data transfer rates: 4, 8, 16, 19, 24, 32, 48, 64, 96, 128, 192 and 250 kbit/sec ( 64k/128k default )
  • UART data transfer rates: 2400, 4800, 9600, 19200, 38400, 57600, 115200 baud  ( 57600 default )
  • Receive Sensitivity: >121 dBm at low data rates, high data rates (TBA)
  • Size: 30 mm (wide) x 57 mm (long) x 12.8 mm (thick) - Including RF Shield, Heatsink and connector extremeties
  • Weight: 14.5g
  • Mounting: 3 x M2.5 screws, 3 x header pin solder points
  • Power Supply: +5 V nominal, (+3.5 V min, +5.5 V max), ~800 mA peak at maximum power
  • Temp. Range: -40 to +85 deg C

Software / GCS Support:

The software solution is an open source development called "SiK" originally by Mike Smith and improved upon by Andrew Tridgell and RFDesign. A boot loader and interface is available for further development and field upgrade of the modem firmware via the serial port.

Most parameters are configurable via AT commands, Eg. baud rate (air/uart), frequency band, power levels, etc., please see the 3DR wiki for commands below for now.

V2.x firmware has been updated to support multipoint networking on the RFD900.

V1.x (non multipoint) is suitable for point to point links - the sourcecode is located at:   https://github.com/RFDesign/SiK

The user manual / datasheet can be found here : RFD900 Datasheet

RFD900 configuration tool and firmware repositoryRFDesign Files

3DR/RFD900 compatible configuration tool : http://vps.oborne.me/3drradioconfig.zip

Wiki for the 3DR radios (RFD900 has same commands): http://code.google.com/p/ardupilot-mega/wiki/3DRadio

Integrated support for configuring the RFD900 radios is supported by APM Planner, with other GCS solutions in development.

The default settings are at 57600 baud, N, 8, 1, and 64k air data rate.

Software features include:

  • Frequency hopping spread spectrum (FHSS)
  • Transparent serial link
  • Point to Point, or Multipoint networking
  • Configuration by simple AT commands for local radio, RT commands for remote radio
  • User configurable serial data rates and air datarates
  • Error correction routines, Mavlink protocol framing (user selectable)
  • Mavlink radio status reporting (Local RSSI, Remote RSSI, Local Noise, Remote Noise)
  • Automatic antenna diversity switching on a packet basis in realtime
  • Automatic duty cycle throttling based on radio temperature to avoid overheating
  • Dynamic transmit power control - reduces transmit power to save battery when close in.

 Compliance :

 The RFD900 is designed to be compliant with the following standards:

  • FCC Part 15.247 (Frequency hopping and digitally modulated intentional radiators)
  • AS/NZS 4268:2012 (Radio equipment and systems - short range devices)


 This modem has been the result of the efforts of a number of people who have collaborated to develop hardware, software and field trial these units.  Developments are still happening to support various GCS and autopilot platforms.  Specifically acknowledging key contributors:

  • Mike Smith - Original SiK firmware for Si1000 based radios.
  • Andrew Tridgell - FHSS, Mavlink, Error Correction, Local/Remote protocol, Field trials, *much more* and awesome ideas on improving things.
  • David Buzz - Field testing, Motivation! and ideas.
  • Micheal Oborne - Integration with APM Planner, and 3DR radio configurator, field trials