Q: How to Set Up RFdesign Telemetry Radios with ArduPilot and PX4

Quick Answer

Setting up RFdesign telemetry radios with ArduPilot or PX4 takes about 15 minutes. Connect the air radio to your Pixhawk's TELEM2 port using a telemetry cable, plug the ground radio into your PC via USB, then connect through Mission Planner or QGroundControl at 57600 baud. RFdesign radios ship pre-paired, so no firmware flashing is needed for most setups.

What You Need

For help choosing between the two modem types, see our RFD900x vs RFD868x comparison. You can browse the full range on the RFdesign collection page.

Step 1: Identify Your Radios

RFdesign modems ship as a pre-configured pair. One radio is the "air" unit (mounted on the drone) and the other is the "ground" unit (connects to your PC). Check the labels or packaging to tell them apart. Out of the box, both are set to 57600 baud, MAVLink protocol, and the same Net ID so they will link automatically.

Step 2: Connect the Air Radio to Your Pixhawk

Locate the TELEM2 port on your Pixhawk. While some guides mention TELEM1, ArduPilot's own documentation recommends against using TELEM1 for RFD900 radios because they can draw up to 800mA at full transmit power, which is close to the port's 1A limit. Use TELEM2 instead, or better yet, power the radio from a separate 5V BEC and only connect TX, RX, and GND to the telemetry port.

Use a 75cm telemetry cable or the shorter 30cm multi-cable to wire the radio to the port. The pinout is standard: TX, RX, 5V, and GND. Double-check that TX on the radio goes to RX on the Pixhawk and vice versa. Mount the radio on your frame away from your video transmitter, ESCs, and other sources of RF interference. A 5.8GHz VTX next to a 900MHz data link will cause packet loss.

For more on cable options, see our Pixhawk telemetry cables guide.

Step 3: Configure ArduPilot Serial Parameters

Connect your Pixhawk to your PC via USB and open Mission Planner. Go to Config/Tuning > Full Parameter List. Set the following for TELEM2 (Serial2):

• SERIAL2_PROTOCOL = 2 (MAVLink 2)
• SERIAL2_BAUD = 57 (57600 baud)

For PX4, open QGroundControl and go to Vehicle Setup > Parameters. Search for "SERIAL" and set the corresponding UART to MAVLink protocol at 57600 baud.

Step 4: Connect the Ground Radio

Plug the ground radio into your PC using a micro-USB cable. It will appear as a serial device (COM port on Windows, /dev/ttyUSB on Linux or macOS). Modern operating systems generally do not need additional drivers.

Step 5: Connect Mission Planner

1. Open Mission Planner
2. Click the "Connect" button in the top-right corner
3. Select the COM port assigned to your ground radio
4. Set the baud rate to 57600
5. Click Connect

If everything is wired correctly and both radios are powered, the HUD will populate with telemetry data and the connection indicator turns green. The green LED on each radio will be solid when the link is established.

Step 6: Test the Link

Power on both the drone and ground station. Walk a short distance away and watch the RSSI indicator in Mission Planner. A stable connection at 100 metres with the stock antennas confirms your setup is working.

For longer range, take the setup to an open area and gradually increase distance while maintaining line of sight. If signal drops earlier than expected, check antenna orientation and make sure the radio is not shielded by carbon fibre or metal parts of the frame. Our antenna selection and range testing guide covers this in detail.

Troubleshooting

• No connection: Check TX/RX wiring is not crossed. TX on the radio must go to RX on the Pixhawk. Verify the correct telemetry port is configured and the baud rate matches on both sides.
• Intermittent connection: Move the telemetry radio away from the VTX and ESCs. RF noise from these components corrupts packets. Adding ferrite chokes to the serial cable can also help.
• Radio resets during transmit: The power supply is insufficient. Use a dedicated 5V BEC capable of at least 1A rather than drawing power from the Pixhawk port.
• Wrong baud rate: The RFdesign default is 57600. If the radios have been reconfigured, use the RFdesign configurator tool in Mission Planner (initial setup screen) to reset them.
• PX4 not connecting: Make sure MAVLink is enabled on the correct serial port in QGroundControl. Some PX4 builds only enable MAVLink on USB by default.

What to Buy

• RFdesign RFD900x modem — the standard long-range telemetry radio for 900MHz regions
• Pixhawk telemetry cable (75cm) — plugs RFD radios straight into Pixhawk TELEM ports
• RFD900x multi-cable (30cm) — shorter option for tighter builds

Need the full picture? Browse all RFdesign products on the RFdesign collection page, or read our guide to building a complete long-range data link.

Frequently Asked Questions

Do I need to flash firmware on the radios?

No. RFdesign radios ship with SiK firmware pre-installed and pre-configured as a matched pair. You only need to update firmware if you want newer features or are troubleshooting a specific issue. The RFdesign configurator in Mission Planner handles firmware updates.

Which TELEMETRY port should I use?

Use TELEM2. ArduPilot's documentation warns against using TELEM1 for RFD900 radios because the radio can draw close to 1A at full transmit power. If TELEM2 is occupied, use another serial port and configure the corresponding SERIALx parameters. In all cases, consider powering the radio from an external 5V BEC rather than the flight controller port.

Can I use these with a Raspberry Pi ground station?

Yes. The ground radio connects via USB and appears as a serial device. You can run MAVProxy, QGroundControl, or any MAVLink-compatible ground station software on the Pi. This is a common setup for survey drones that need a portable ground station in the field.