Description
RadioMaster DBR4: dual-band ExpressLRS Gemini receiver
The RadioMaster DBR4 is an ExpressLRS Gemini Xrossband receiver with two LR1121 chips. Each half receives on 2.4 GHz and 900 MHz at the same time, so the link arrives on two frequencies at once and copes better with interference and packet loss.
It is the receiver designed to go with the RadioMaster Nomad module. It weighs 5.3 g with antennas and mounts on 20 × 20 mm holes.
RadioMaster DBR4 specifications
- Version: FCC, manufacturer code HP0157.0086
- Protocol: ExpressLRS Gemini Xrossband (GemX), with ExpressLRS 3.3.2 installed from the factory
- Frequencies: 2.404 to 2.479 GHz and 903.5 to 926.9 MHz
- Processor: ESP32, with 2 Semtech LR1121 radio chips
- Antennas: 4 wire antennas, 2 for 2.4 GHz and 2 for 900 MHz
- Telemetry power: up to 100 mW
- Refresh rate: 50 to 500 Hz
- Flight controller connection: CRSF
- Power: 4.5 to 8.4 V
- Weight: 2.7 g without antennas and 5.3 g with antennas
- Size: 27.2 × 27.2 mm, 20 × 20 mm mounting holes
What is in the box
- 1 RadioMaster DBR4 receiver
- 2 wire antennas for 2.4 GHz
- 2 wire antennas for 900 MHz
- 1 CRSF cable
- 8 vibration dampers: 4 red 4 mm and 4 black 3 mm
- 1 manual card
FCC version: what to do in Europe
This RadioMaster DBR4 is the FCC version: the 900 MHz band is set to 903.5-926.9 MHz, the one used in the United States. In Europe the Sub-GHz band for radio control is 868 MHz.
To use the Sub-GHz band here, flash the receiver and your module with ExpressLRS firmware using the EU 868 domain, which you choose when flashing with ExpressLRS Configurator. The 2.4 GHz part works without changes.
Which drone the RadioMaster DBR4 is for
It suits 3 to 7 inch drones with a flight controller that supports CRSF and room for a 20 × 20 mm receiver, especially for long range flights or areas with a lot of radio noise, where two bands at once give you margin.
To use both bands at once you need an ExpressLRS Gemini Xrossband module or radio, such as the RadioMaster Nomad. Before buying, check that your flight controller has a free UART and that your radio runs a compatible ExpressLRS version.
Why a dual-band receiver
The 2.4 GHz band allows high packet rates and small antennas. The Sub-GHz band reaches further and gets through obstacles better. With Gemini the receiver gets both at once: if one gets noisy, the other keeps delivering the packets.
Frequently asked questions about the RadioMaster DBR4
Is this the LBT or European version?
No. It is the FCC version, code HP0157.0086. For the Sub-GHz band in Europe it has to be flashed with the EU 868 domain.
Are the antennas included?
Yes. It comes with the 4 wire antennas, the CRSF cable and the vibration dampers.
What voltage does it run on?
From 4.5 to 8.4 V. It is usually connected to a 5 V pad on the flight controller.
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