RFD is a long-range telemetry and communication system (over 40 km). An RFD system consists of two RFD modems, a set of antennas and the cables needed to connect the modules to other systems.
How an RFD system is built
At the heart of every system are RFD modems – high-performance radio modems operating in the ISM (Industrial, Scientific and Medical) band. They are designed for long-range communication applications that require best-in-class radio link performance. One modem is always part of the GCS (Ground Control Station), while the other is part of the project that needs to communicate, e.g. an unmanned aerial vehicle.
RFD868x set. Source: store.rfdesign.com.au
Product features:*
- long range, over 40 km depending on antennas and GCS setup. Edge Research Laboratories demonstrated operation at a distance of 80 km using a balloon,
- 32-bit ARM core,
- hardware-accelerated AES encryption,
- RC PPM passthrough with simultaneous telemetry,
- 2x RP-SMA RF connectors, diversity switched,
- transmit power: 1 W (+30 dBm),
- low-pass filtered transmission,
- >20 dB low-noise amplifier, high IP3,
- RX SAW filter,
- all inputs/outputs ESD-protected and filtered,
- re-implemented SiK and Multipoint SiK firmware, field-upgradeable and easy to configure,
- small and light.
*Some parameters may differ depending on the product version
Software / GCS support:
The software is an open-source program called “SiK”. It was re-implemented to fit the new processor architecture of the 32-bit ARM core. The bootloader and interface are available for further development and for updating the modem firmware over the serial port. Most parameters can be configured with AT commands, e.g. data rate (air / UART), frequency band and power levels. Integrated configuration of RFD900 radios is supported by APM Planner.
Software features include:
- Frequency-hopping spread spectrum (FHSS)
- Transparent serial link
- Point-to-point or multipoint network
- Configuration with simple AT commands for the local radio and RT commands for the remote radio
- User-configurable serial data rates and air data rates
- Error correction routines and 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 real time
- Automatic duty-cycle throttling based on radio temperature to avoid overheating
Available variants
There are many versions of RFD modems on the market, including: RFD868x, RFD900x, RFD868ux, RFD868x-EU, and others.
RFD modems are made for two frequency bands. Depending on size and certification type, RFD868 versions operate in the 865–870 MHz range, the ISM band commonly used in Europe. RFD900 versions operate in the 902–928 MHz range, the US ISM band.
The “x” or “ux” in the name indicates the module size. RFD modules marked “x” are standard-size versions measuring 50x30x12.8 mm and weighing 14.5 g. The “ux” marking refers to the micro version, smaller at 33x25x10.4 mm and weighing 10 g.
The name may also include a symbol indicating compliance with the regulations of a given region. RFD modems are available with certifications required in the following regions: EU, US, AU, IND and NZ.
The basic condition for two RFD modems to communicate is that both operate in the same frequency band. Standard and micro versions can be compatible with each other as long as they are configured with the same operating parameters. Things get more complicated with compatibility between certified and non-certified modems. In that case, check the compatibility of the specific versions, ideally on the manufacturer's or distributor's website.
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RFD TXMOD V2
The RFD TXMOD 868 V2 module is designed to work with radio transmitters that accept JR transmission modules. The device has a built-in WiFi module that enables web-page-based configuration and sending telemetry data to a computer or mobile device.
JR modules plug into transmitters with JR bays (FrSky Taranis, JR, FrSky Horus), establishing a link between the transmitter and the drone that carries PPM and MAVLink telemetry at the same time.
RFD900x TXMOD V2 set and RFD TXMOD V2 plugged into a transmitter (Source: www.worldronemarket.com)
Technical specifications of selected RFD modules compared
Applications of the RFD communication system
RFD systems are used wherever a connection and real-time transmission of telemetry data over long distances is required. They are most often used in unmanned aircraft systems. They can also be found in long-range autonomous boats, rovers and industrial transport robots. According to the manufacturer, RFD systems are also used in remote weather stations and in home automation.
RFD900x modules were used in the Avartek Boxer Hybrid drone, a petrol-powered UAV.
NOVAerial Robotics used the RFD900+ system in the second phase of beta testing of its Procyon 800E rotorcraft. (Source: www.suasnews.com)
How to configure the system is described on the manufacturer's official website rfdesign.com. The modules can also be configured with Mission Planner. Instructions are available at ardupilot.org.
Sources:
https://bzbuas.com/sklep/czesci-do-dronow/modemy-lacznosci-i-telemetria/
https://store.rfdesign.com.au/radio-modems/
http://rfdesign.com.au/products/
https://www.youtube.com/c/MadRC
https://www.worldronemarket.com/product/rfd900-txmod-v2-bundle/