LR900 Telemetry Radio — User Manual
Introduction
The LR900 is a series of long-range telemetry radios designed and manufactured by MicoAir. It operates in the 890–915 MHz band and uses LoRa spread-spectrum modulation together with FHSS (frequency-hopping spread spectrum), giving it strong interference rejection and high receive sensitivity. It supports transparent serial passthrough and is compatible with mainstream open-source flight controllers and ground control station (GCS) software. It can be used as the link between ArduPilot/PX4 flight controllers and GCS software such as Mission Planner or QGroundControl, and also as the data link between an RTK base station and rover.
Where to buy
Available from Robofusion: robofusion.net (link to your LR900 product page)
Model variants
- LR900-A: max transmit power 22 dBm, no enclosure
- LR900-F: max transmit power 27 dBm
- LR900-P: max transmit power 30 dBm
The LR900-A uses a CH340 USB-to-TTL chip; all other models use the CP2102.
The variants have different transmit powers but can all be paired with one another. Link range is generally limited by whichever end has the lower transmit power.
Specifications
| Parameter | Value |
|---|---|
| Operating band | 890–915 MHz |
| Transmit power | 1000 mW (LR900-P); 500 mW (LR900-F); 160 mW (LR900-A) |
| Max transparent throughput | 2.1 KB/s; 3.2 KB/s (FHSS downlink; not supported on LR900-A) |
| Max serial single-packet length | 4 KB (LR900-A); 8 KB (LR900-F/P) |
| Communication interface | LVTTL (3.3 V) serial; USB Type-C |
| Serial baud rate | Default 57600 |
| Antenna connector | SMA (external thread, center socket) |
| Supply voltage | 4.5–5 V |
| Max average power consumption | 2 W (LR900-P); 1 W (LR900-F); 300 mW (LR900-A) |
Dimensions
LR900-F/P dimensions (mm):
- Weight: 8 g
- 3D model (STP)
Interfaces
The LR900 has two external interfaces:
- A 3.3 V TTL serial port (connector type GH1.25-4P), typically used to connect directly to a flight controller's serial port.
- A USB Type-C port, used to connect to a computer (the matching USB-to-TTL driver must be installed on the computer). Note: the USB port cannot be used to connect directly to a flight controller.
- Tx: serial Tx — connect to the flight controller's serial Rx
- Rx: serial Rx — connect to the flight controller's serial Tx
- 5V: power, 5 V
- GND: power ground
Configuration software and drivers
You can configure the radio's parameters with the MicoAir Assistant. MicoAir now also offers a browser-based configurator at micoair.com/assistant, which replaces the older installed desktop version.
USB-to-TTL drivers:
- CH340 driver download (LR900-A)
- CP2102 Driver Installation Guide (Windows) (LR900-F/P)
LED indicator
The LR900 has a single green LED that indicates link status:
- Blinking at 1 Hz: telemetry not connected
- Solid on: telemetry paired and connected normally
How the radios pair
If two LR900 modules have matching parameters (all units ship with the same defaults), they connect automatically on power-up. If you need several pairs of radios to operate at the same time, set a different module address for each pair (see the parameter descriptions below).
Telemetry parameters
Operating mode
The LR900 supports three modes: duplex, broadcast-transmit, and broadcast-receive. Default is duplex.
When used as a flight-controller telemetry link, only duplex mode can be used. In broadcast-transmit/receive mode the unit can only send or only receive data — typically used for RTK base-station and rover devices.
Throughput (air data rate)
The LR900 supports three rate modes; default is high-speed, with a symmetric up/down rate of 2.1 KB/s (i.e. 2.1 K bytes per second). For flight-controller telemetry, only high-speed mode is recommended.
Frequency mode
- LR900-A supports two frequency modes: manual / auto.
- LR900-F/P support four: manual / auto / FHSS-GROUND / FHSS-AIR.
Default is auto, where the operating frequency is selected automatically. In manual mode you set the frequency point yourself.
FHSS is frequency-hopping mode, recommended for flight-controller telemetry: set the end connected to the flight controller to FHSS-AIR, and the end connected to the computer to FHSS-GROUND. In FHSS mode the downlink (flight controller → computer) rate is higher, up to 3.2 KB/s. Note: the LR900-A does not support FHSS.
Frequency point
Only takes effect in manual frequency mode. Values 0–25 correspond to 890–915 MHz.
Module address
Default 1000. Only two modules with the same address can communicate. When running several pairs of radios at once, set this to different values; range 1–30000.
Serial baud rate
Baud rate of the GH1.25 interface. Supports 9600 / 19200 / 38400 / 57600 / 115200; default 57600.
USB baud rate
Baud rate of the USB Type-C interface. Supports 57600 / 115200; default 57600.
Setup tutorials
Translated and adapted into English by Robofusion from MicoAir's official manual. Original (Chinese): LR900数传电台用户手册. Last updated upstream: 2025-07-10.