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    RDF900 Diversity Telemetry modem.
    RDF900 Telemetry Modem

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    Our Price: $89.50

    Stock Status:(Out of Stock, usually arrives every 2 weeks)
    Availability:: Usually Ships in 2 to 3 Business Days
    Product Code: RDF900MDM1

    RFD900 Long range Telemetry & diversity modem

    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.

    Dont forget to have:

    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 / 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 connectors
    • 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 on the RDF900

    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)
    • 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

    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.

    The software solution is compatible with the "3DR" line.

    Latest source is located at:

    Configuration tool :

    Wiki for the 3DR radios (RFD900 has same commands):

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


    Software features include:

    • Frequency hopping spread spectrum (FHSS)
    • Transparent serial link
    • 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

    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

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