1. Introduzzjoni
The RADIOMASTER XR4 Gemini Xrossband Dual-Band Receiver is designed for remote control applications, offering reliable signal reception through its dual-band capabilities. It supports ExpressLRS Gemini Xrossband (Gem-X) protocol, operating on both 2.4GHz and Sub-G 900MHz frequencies. This manual provides essential information for the proper setup, operation, and maintenance of your XR4 receiver.
2. Kontenut tal-Pakkett
Iċċekkja li l-oġġetti kollha elenkati hawn taħt huma inklużi fil-pakkett tiegħek:
- 1 x XR4 Gemini Xrossband Dual-Band Receiver
- 2 x Dual-Band T-Antenna
- 1 x CRSF Wire
- 3 x Tubu li Jiċkien bis-Sħana

This image displays the Radiomaster XR4 receiver board with its two dual-band T-antennas attached, illustrating the complete receiver assembly.
3. Karatteristiċi
- True Diversity & Dual-Band: Utilizes dual LR1121 RF transceivers for enhanced reliability.
- ExpressLRS Gemini Xrossband (Gem-X) Compatible: Supports 2.4GHz and Sub-G 900MHz bands.
- MCU ta' Prestazzjoni Għolja: Equipped with ESP32D4.
- Dual Semtech LR1121 Transceivers: Provides robust signal processing.
- Secondary UART Port: For advanced functionality and future expansion.
- Castled Pads: Facilitates easy soldering.
- Integrated Wi-Fi Module: Simplifies firmware updates and configuration via WebUI
- Ultra-Low Latency & High Refresh Rate: Ensures stable RF link.

This image highlights the two Semtech LR1121 transceivers, which are central to the receiver's dual-band and true diversity capabilities.

Din l-immaġni turi dettaljata view of the XR4 receiver board, specifically pointing out the additional UART port available for future expansion and advanced functionality.
4. Speċifikazzjonijiet
| Parametru | Valur |
|---|---|
| MCU | ESP32D4 |
| Ċippa RF | LR1121 x 2 |
| Konnettur RF | IPEX-1 x 2 |
| Antenna | Dual-Band T Antenna x 2 (Included) |
| Medda ta' Frekwenzi | 2.4GHz / Sub-G 900MHz |
| Qawwa tat-Telemetrija | 100mW |
| Rata Massima ta' Riċeviment ta' Aġġornament | DK500Hz / K1000Hz |
| Minimum Receiver Refresh Rate | 50Hz |
| Ħidma Voltage | DC 4.5-8.4V |
| Piż (mingħajr antenna) | 1.7g |
| Dimensjonijiet | 22mm x 18mm x 4mm |
| Firmware Version (pre-installed) | ExpressLRS v3.5.1 |
| Mira tal-FW | RadioMaster XR4 2.4/900 Gemini RX |
| Interface tax-xarabank 1 | CRSF |
| Interface tax-xarabank 2 | UART |

Din l-immaġni tipprovdi veduta ċara minn fuq għal isfel view of the XR4 receiver's circuit board, showing component layout and connection points.

Din l-immaġni turi vantaġġ tal-ġenbfile of the XR4 receiver board, with "XR4 V1.00" clearly visible, indicating the model and version.
5. Setup u Installazzjoni
5.1 Konnessjonijiet tal-Wiring
The XR4 receiver uses standard CRSF protocol for communication. Connect the receiver to your flight controller or other compatible device using the provided CRSF wire. Ensure correct polarity for power connections (DC 4.5-8.4V).
- 5V: Power input (4.5-8.4V DC)
- GND: Art
- TX: CRSF Transmit (connect to RX on flight controller)
- RX: CRSF Receive (connect to TX on flight controller)
- TX2/RX2: Secondary UART port for advanced functionality.
5.2 Installazzjoni tal-antenna
Connect the two dual-band T-antennas to the IPEX-1 connectors on the receiver board. Position the antennas at a 90-degree angle to each other for optimal signal diversity. Use the provided heat-shrinkable tubes to secure and protect the antenna connections.

Din l-immaġni turi angolat view of the XR4 receiver board, highlighting the IPEX-1 antenna connectors and the soldering pads for power and CRSF communication.
6. Istruzzjonijiet Operattivi
6.1 Binding Procedure (ExpressLRS)
The XR4 receiver comes pre-installed with ExpressLRS v3.5.1 firmware. To bind the receiver to your ExpressLRS transmitter module, follow these general steps:
- Ensure your transmitter module is running a compatible ExpressLRS firmware version.
- Power on the receiver. It will enter binding mode if it does not find a valid link. The LED on the receiver will typically flash rapidly.
- On your ExpressLRS transmitter, initiate the binding process. This is usually done via the Lua script or a dedicated bind button/menu option.
- Ladarba jkun hemm konnessjoni, l-LED tar-riċevitur jixgħel b'mod solidu, u dan jindika konnessjoni b'suċċess.
- If binding fails, ensure your transmitter and receiver have matching ExpressLRS firmware versions and binding phrases (if configured).
6.2 Operating Modes: Gemini and Xrossband (Gem-X)
The XR4 receiver supports various operating modes, leveraging its dual RF circuits:
- Gemini 2.4GHz: Uses two 2.4GHz antennas for dual-frequency operation within the 2.4GHz band.
- Gemini Sub-G 900MHz: Uses two 900MHz antennas for dual-frequency operation within the Sub-G 900MHz band.
- Xrossband (Gem-X): Utilizes one Sub-G 900MHz antenna and one 2.4GHz antenna for dual-band operation, providing enhanced reliability across different frequency ranges.
The specific mode is typically configured via the ExpressLRS Lua script on your transmitter or through the receiver's WebUI

This diagram visually explains the different antenna configurations and packet transmission methods for Gemini 2.4GHz, Gemini Sub-G 900MHz, and Xrossband (Gem-X) dual-band modes.
7. Aġġornamenti tal-Firmware
The XR4 receiver features an integrated Wi-Fi module for convenient firmware updates and configuration. To update the firmware:
- Qawwa fuq ir-riċevitur.
- Connect to the receiver's Wi-Fi hotspot from your computer or mobile device. The network name will typically be "ExpressLRS RX" followed by a unique identifier.
- Iftaħ a web browser u naviga għal http://10.0.0.1.
- Uża l- WebUI to flash new firmware or adjust settings. Refer to the official ExpressLRS documentation for detailed instructions on firmware flashing.
8. Manutenzjoni
The XR4 receiver requires minimal maintenance. Keep the device clean and free from dust and moisture. Regularly inspect antenna connections for damage. Ensure proper heat dissipation if operating in enclosed spaces.
9 Issolvi l-problemi
- Ebda Link/Teptip tal-LED:
- Ensure the receiver is powered correctly (4.5-8.4V).
- Verify the transmitter module is powered on and transmitting.
- Check if the receiver is in binding mode (rapid LED flash). If not, re-initiate binding.
- Confirm that the transmitter and receiver are running compatible ExpressLRS firmware versions.
- Check for correct binding phrase if one is set.
- Firxa/Kwalità tas-Sinjal Fqira:
- Inspect antennas for damage or improper connection.
- Ensure antennas are positioned optimally (e.g., 90 degrees to each other).
- Check for sources of interference near the receiver or antennas.
- Verify the selected operating mode (Gemini/Xrossband) is appropriate for your setup.
- Ir-Riċevitur Mhux Jirrispondi:
- Check all wiring connections (power, ground, CRSF TX/RX).
- Ensure the flight controller or connected device is configured correctly for CRSF protocol.
- Attempt a firmware re-flash if the receiver is unresponsive.
10. Informazzjoni dwar is-Sigurtà
- Always ensure correct power polarity before connecting the receiver. Incorrect wiring can cause permanent damage.
- Operate RC equipment responsibly and within legal limits.
- Keep the receiver away from water, moisture, and extreme temperatures.
- Do not attempt to modify the receiver's hardware beyond specified connection points.
- Żgura ventilazzjoni xierqa biex tevita sħana żejda.
11. Garanzija u Appoġġ
Għal informazzjoni dwar il-garanzija u appoġġ tekniku, jekk jogħġbok irreferi għar-RADIOMASTER uffiċjali webis-sit jew ikkuntattja lin-negozjant awtorizzat tiegħek. Żomm il-prova tax-xiri tiegħek għal talbiet ta' garanzija.





