Quick Answer
A drone telemetry radio sends real-time flight data (GPS position, battery voltage, altitude, attitude) from your aircraft to a ground station computer over a long-range wireless link. Popular options include Microhard P900 and P400 radios from Holybro, which support mesh networking and reach up to 40 miles line-of-sight.
What Telemetry Radios Actually Do
Telemetry radios create a wireless serial link between your drone's flight controller and a ground station running software like QGroundControl or Mission Planner. They carry MAVLink data, which includes GPS coordinates, battery status, speed, altitude, and command acknowledgements.
Without a telemetry link, you are flying blind after the craft leaves visual range. Telemetry lets you monitor every aspect of the flight, trigger autonomous missions, and react to problems in real time.
Telemetry radios are different from your RC control link (ELRS, Crossfire, or a standard RC transmitter). The control link sends stick inputs to the aircraft. The telemetry link sends sensor data back to you. Both are needed for serious beyond-visual-line-of-sight (BVLOS) or long-range flying.
If you are building around a Pixhawk flight controller, telemetry is one of the first peripherals worth adding. Most Pixhawk boards, including the Pixhawk 5X and Pixhawk 6 series, have dedicated TELEM ports designed for this purpose.
P900 vs P400: Choosing the Right Frequency
| Feature | P900 | P400 |
|---|---|---|
| Frequency Band | 902-928 MHz | 400-470 MHz |
| Best For | North America | UK, EU, and international |
| Range | Up to 40 miles | Up to 40 miles |
| Max Power | 1W (software selectable) | 1W (software selectable) |
| Data Rate | Up to 276 Kbps | Up to 276 Kbps |
The P900 operates in the 900 MHz ISM band, which is licence-exempt in the US but restricted in many other countries. The P400 uses the 400 MHz band, making it a better choice for UK and European operators. Both use frequency hopping spread spectrum (FHSS) to avoid interference and provide reliable data transfer.
Check your local regulations before transmitting. In the UK, Ofcom sets the rules for licence-exempt radio equipment, and power limits may differ from the module's maximum output.
Connecting Your Telemetry Radio
Setup is straightforward with Pixhawk-compatible radios. The Holybro Microhard V2 ships with a 6-pin JST-GH cable that plugs directly into the TELEM1 port on any Pixhawk-standard flight controller. The radio needs separate power via the included XT30 cable (7-35V DC). On the ground side, the radio connects to your computer through USB-C.
Pin mapping on the Pixhawk TELEM port follows the standard convention: TX, RX, VCC (5V), GND, CTS, RTS. The radio's JST-GH connector matches this pinout, so no wiring diagram is needed.
Configuring the Link
Out of the box, the Microhard V2 radios are configured for point-to-point mode at 57600 baud. This works with both PX4 and ArduPilot without any changes. Simply connect both radios, power them on, and open QGroundControl (for PX4) or Mission Planner (for ArduPilot). The ground station should detect the MAVLink stream automatically.
If you need to change the baud rate, switch to mesh mode, or adjust power output, use the PicoConfig application from Microhard. You connect to the radio's diagnostic port (4-pin JST SH) with a USB-to-serial adapter. Hold the Config button while powering up to enter command mode.
For mesh networking with multiple vehicles, each radio needs a unique MAVLink system ID. The mesh supports up to 201 nodes at the highest link rate, with automatic routing and retransmission.
What to Buy
- Holybro Microhard V2 Telemetry Radio (P900/P400) - Long-range MAVLink link with mesh support, up to 40 miles
- Pixhawk 5X Autopilot Kit - Flight controller with dedicated TELEM ports for radio connection
Browse the full maker collection for other components to complete your build.
FAQ
Q: Do I need a telemetry radio if I already have a long-range RC link?
A: Yes. Your RC link (ELRS, Crossfire) sends control inputs from your transmitter to the drone. A telemetry radio sends flight data back the other way. For autonomous missions and live monitoring, both links are needed.
Q: Which frequency should I use in the UK?
A: The P400 (400-470 MHz) is the better choice for the UK. The P900 operates in the 900 MHz band, which has different regulatory restrictions outside North America. Always check Ofcom's current guidance before transmitting.
Q: Can one ground station radio talk to multiple drones?
A: Yes. The Microhard radios support point-to-multipoint and mesh modes. In mesh mode, each vehicle needs a unique MAVLink system ID. A single ground radio can monitor and control dozens of aircraft simultaneously, depending on the data rate and FEC settings.