RadioMaster DBR4 Dual Band Gemini Xrossband ExpressLRS Receiver, 2.4GHz + 915MHz, CRSF for RC/FPV
RadioMaster DBR4 Dual Band Gemini Xrossband ExpressLRS Receiver, 2.4GHz + 915MHz, CRSF for RC/FPV
RadioMaster
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Overview
The RadioMaster DBR4 is a dual band ExpressLRS receiver designed as a companion to the RadioMaster Nomad module. It is a dual-channel Gemini receiver with two dual-band sections, allowing simultaneous reception of 2.4GHz and sub-GHz (900/915MHz) signals for receiving two data streams at the same time.
Key Features
- Gemini Xrossband (Gemini-X / GemX) operation (2.4GHz + 900/915MHz)
- Dual band diversity
- Two third-generation Semtech LR1121 RF transceivers (Dual LR1121)
- 4 discrete antennas for flexible antenna placement
- 20 x 20mm mounting pattern (for adding to a stack or mounting to a frame)
- MAVLink ready; optimized for MAVLink
- Xrossband (GemX) support
Specifications
| Item | DBR4 Gemini Xrossband ExpressLRS Receiver |
| Type | ISM_2.4, FCC_915 (also listed as ISM 2.4GHz / FCC 915MHz) |
| MCU | ESP32 |
| RF chip | Semtech LR1121 x 2 |
| Telemetry RF power | Max 2 x 100 mW (feature text); Max 100 mW (specification) |
| Antenna | 2 x 2.4GHz wires & 2 x 900MHz wires (also labeled as 2 x 915MHz wire antennas) |
| Frequency range | 2.404 - 2.479 GHz / 903.5 - 926.9 MHz |
| Maximum receive refresh rate | 500Hz (1000Hz coming soon in ExpressLRS v3.4) |
| Minimum receiver refresh rate | 50Hz |
| Working voltage | DC 4.5 - 8.4V |
| Weight | Without antennas 2.70g (specification); with antennas 5.30g (specification); 2.65g (displayed measurement) |
| Dimensions | 27.20 x 27.20mm (also listed as 27 x 27mm) |
| Mounting holes | 20 x 20mm |
| Firmware version | ExpressLRS v3.3.2 pre-installed |
| Bus interface | CRSF |
| Antenna length (as labeled) | 105.20mm; 16.10mm |
For installation or configuration help, contact https://rcdrone.top/ or email support@rcdrone.top.
New Packet Rates
Sub-GHz 250Hz (-111dBm)
- Speed Boost: Achieve faster packet rates with enhanced sub-GHz performance.
Sub-GHz 200Hz Full (-111dBm)
- Double the packet rate compared to traditional 900MHz SX1276-based modules, with improved resistance to interference.
Dual Band X150Hz (-112dBm)
- Gemini Mode: Simultaneous sub-GHz and 2.4GHz transmissions at 150Hz.
Dual Band X100Hz Full (-112dBm)
- Enhanced Gemini Mode: Dual-frequency transmission at 100Hz with full 16 channel resolution.
Introduction of K Modes
DK500 (Coming in ExpressLRS v3.5)
- Next generation FSK modulation with built-in packet repair (Forward Error Correction). Like FLRC D500, DK500 sends repeat packets to reduce packet loss.
K1000 Full SubGHz (Coming in ExpressLRS v3.5)
- 1000Hz on 868/900MHz, designed for maximum data throughput while remaining stable and responsive in testing.
What’s Included
- 1 x DBR4 Gemini Xrossband ExpressLRS Receiver
- 2 x 2.4GHz wire antennas
- 2 x 900MHz wire antennas
- 1 x CRSF wire
- 4 x 4mm red vibration dampeners
- 4 x 3mm black vibration dampeners
- 1 x Manual card
Manuals / Documentation
ExpressLRS project documentation: https://www.expresslrs.org/
Details
DBR4 is a dual-band Gemini Xrossband ExpressLRS receiver built to receive 2.4GHz and 900/915MHz links at the same time.
Two third-generation Semtech LR1121 transceivers power the dual-band design for Gemini-X and Xrossband use.
Four discrete antennas make it easy to route and separate 2.4GHz and sub‑GHz elements for cleaner placement on compact builds.
A 20×20mm mounting pattern fits common FPV stacks and frame mounting options.
CRSF output and MAVLink-ready tuning help support reliable telemetry and flight-controller communication.
Key specs at a glance: 4.5–8.4V input, up to 500Hz refresh rate, and dual-band 2.4GHz plus 903–927MHz coverage.
The receiver weighs about 2.65g without antennas for minimal impact on all-up weight.
Included are the DBR4 receiver, 2× 2.4GHz wire antennas, 2× 915MHz wire antennas, a CRSF cable, and vibration dampeners.
