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RFDesign makes a fantastic modem and other items used in long distance UAVs and other projects. The modem is small and light weight and has amazing capabilities.
I have spoken with the head of the company, Seppo Saario. He is a real great guy who quickly got behind Project ThunderStruck. We have discussed their modems before, but this is the first time that we can actually use their equipment in a project, although we intend to use the modems in a lot of balloon projects. This will especially be the case in the coming weeks as we test for ThunderStruck. Given a good yagi antenna on the ground and a well oriented patch antenna on the aircraft, communications up to 80km is possible.
We intend to use these modems for the two way data from Thunderstruck. The units operate at 900MHz and produce about 1 watt. Two units are paired on the ground by setup via a PC. They can communicate at speeds of up to 56Kb nominally or even higher. Way faster than our needs. Rather than the usual APRS system that we currently use that give updates every 20 seconds or the Spot3 system that updates every 10 minutes, this system is capable of 1 second updates of speed and other data. Our flight controls will also be very responsive if coupled correctly. They will work well with the PIXHAWK flight controllers and I have some good news about support from them shortly. Just a simple cable is needed to connect the PixHawk Autopilot to the RFD900
More on PixHawk later. Now about this amazing modem. From their website:
RFDesign is an electronics design and manufacturing company specialising in Embedded systems, Radios, Antennas and high frequency electronics. We are located in Brisbane, Australia with our office located in Acacia Ridge, QLD.
- 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 SiK (V1.x) / tools, field upgradeable, easy to configure.
- Multipoint software capability with MP SiK (V2.x)
- 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 TTL (+3.3v nominal, +5v tolerant)
- Power: +5v, ~800mA max peak (at maximum transmit power)
- GPIO: 6 General purpose IO (Digital, ADC, PWM capable).
- Frequency Range: 902 – 928 MHz (USA) / 915 – 928 MHz (Australia)
- Output Power: 1W (+30dBm), controllable in 1dB steps ( +/- 1dB @=20dBm typical )
- Air Data transfer rates: 4, 8, 16, 19, 24, 32, 48, 64, 96, 128, 192 and 250 kbit/sec ( User selectable, 64k default )
- UART data transfer rates: 2400, 4800, 9600, 19200, 38400, 57600, 115200 baud ( User selectable, 57600 default )
- 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
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
A software manual for SiK firmware is here : RFD900 Software manual
RFD900 configuration tool: http://rfdesign.com.au/downloads/
RFD900 binary firmware repository: http://rfdesign.com.au/firmware/
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
website, http://rfdesign.com.au for more information.