Introduction
ExpressLRS (ELRS) has become the dominant open-source radio control link for FPV drones, displacing Crossfire, Tracer, and FrSky with its combination of incredible range, ultra-low latency, and affordable hardware. The release of ExpressLRS 4.0 in 2026 represents the most significant update since the 3.x branch, bringing features that push the protocol further ahead of proprietary alternatives.
This guide covers what’s new in ExpressLRS 4.0, how it improves on 3.x, and how to upgrade your existing gear.
What’s New in ExpressLRS 4.0
1. FLRC (Full Link Rate Control) — Adaptive LoRa Modulation
The flagship feature of ELRS 4.0. FLRC dynamically adjusts LoRa spreading factor, bandwidth, and coding rate in real time based on link quality. In practice:
- Close range / high RSSI: Higher data rate, lower latency (~3-4ms packet interval)
- Medium range: Balanced data rate for good telemetry and control
- Edge of range: Maximum sensitivity mode, 500Hz capable even at -112dBm
FLRC eliminates the old “refresh rate vs. range” trade-off. You no longer need to choose between 1000Hz for racing and 50Hz for long range — the link optimizes itself continuously.
2. Gemini X — True MIMO Diversity
Building on the Gemini diversity of 3.x, Gemini X introduces multiple-input multiple-output (MIMO) antenna processing. Both receiver antennas actively decode simultaneously, combining signals for up to 3dB of effective gain improvement. This translates to roughly 40% more range in challenging RF environments (behind buildings, through trees).
Gemini X requires new hardware — the receivers have dual RF front-ends with phase-coherent processing. Compatible modules include the Happymodel ES900RX-D and Radiomaster RP4TD-M.
3. ELRS Backpack 2.0
The backpack protocol (used for VRX communication, head tracking, and telemetry forwarding) has been reworked:
- Native MAVLink passthrough: Full MAVLink telemetry from flight controller to ground station without additional hardware
- Higher bandwidth: 4x throughput for low-latency telemetry (GPS, battery, RSSI to your radio screen)
- WiFi + BLE coexistence: Simultaneous WiFi and Bluetooth, configurable via joystick on the TX module
- OTA updates via Backpack: Update receiver firmware through the TX module wirelessly — no more USB cables
4. Precision LoRa — 32-bit Timestamping
ELRS 4.0 introduces hardware-level packet timestamping with 32-bit precision. Combined with FLRC, this reduces effective control latency by approximately 1.5ms at 500Hz. For racers, this brings ELRS latency closer to wire-range responsiveness.
5. Unified Target System
All ELRS 4.0 hardware now uses a unified firmware target system. Instead of selecting “Happymodel EP1” or “Radiomaster RP1” as separate targets, you select the MCU type (ESP32, ESP8285) and featureset. This dramatically simplifies firmware flashing and reduces the chance of bricking with a wrong target.
6. LBT (Listen Before Talk) CE Compliance Mode
For European pilots, ELRS 4.0 includes a proper LBT implementation that’s actually performant. Unlike the reduced duty cycle workaround used in 3.x, 4.0 LBT mode dynamically senses channel activity and transmits in gaps. Real-world testing shows LBT mode achieves 85-95% of non-LBT range while being fully CE compliant at 100mW+.
Performance Comparison: 3.x vs 4.0
| Metric | ELRS 3.x (1000Hz) | ELRS 4.0 FLRC |
|---|---|---|
| Minimum latency (close range) | ~5ms | ~3.5ms |
| Typical freestyle latency | ~7ms | ~4-5ms |
| Range at 100mW (2.4GHz, open air) | ~30km | ~35-40km |
| Range at 100mW (900MHz, open air) | ~60km | ~75-85km |
| Penetration (behind 3 walls) | Failsafe ~50m | Failsafe ~75m (Gemini X) |
| Telem bandwidth (uplink) | ~200 bps | ~800 bps |
| OTA update | WiFi only | WiFi + Backpack passthrough |
Compatible Hardware
Transmitters Modules
Most ELRS 3.x hardware can be upgraded to 4.0 via firmware. Known compatible TX modules:
- Radiomaster Ranger series: Full 4.0 support including FLRC
- Happymodel ES24TX series: Full support
- BetaFPV SuperG / Nano TX: Full support on ESP32-based modules
- NamimnoRC Flash / Voyager: Full support
- Jumper AION series: Full support (ESP32 models)
Older ESP8285-based modules (some Happymodel EP2, older BetaFPV TX) have limited RAM and may not support all 4.0 features, particularly Gemini X and full FLRC. Check the ExpressLRS website for your specific hardware.
Receivers
- Happymodel EP1/EP2/PP: Full support (ESP32-based)
- Radiomaster RP1/RP2/RP3: Full support
- BetaFPV Nano RX: Full support (ESP32-based)
- Mateksys ELRS-R24: Full support
How to Upgrade to ExpressLRS 4.0
- Backup your current config: In the ELRS Lua script on your radio, note down your binding phrase, power settings, and model match settings
- Download ELRS Configurator 2.0: Required for 4.0 firmware. Available on the ExpressLRS GitHub
- Select unified target: Choose your hardware by MCU type and features (e.g., “ESP32 + SX1280 + PA” for 2.4GHz transmitters)
- Flash TX module: Via USB or WiFi (existing WiFi update method still works)
- Flash RX: Via WiFi or passthrough from flight controller (Betaflight 4.5+ required for passthrough)
- Set binding phrase: Must be identical on TX and RX or they won’t bind
- Verify on Lua script: Check version shows “4.0.x” and FLRC status is “Active”
Should You Upgrade?
For most pilots, upgrading to ELRS 4.0 is worth it for FLRC alone — the dynamic link optimization is genuinely transformative. The upgrade path is smooth and backwards-compatible (4.0 TX binds to 3.x RX in compatibility mode).
Reasons to wait:
- You have older ESP8285 hardware that won’t support full 4.0 features
- You’re mid-race-season and don’t want to change anything
- Your current 3.x setup works perfectly and you don’t need the new features
For everyone else: the upgrade takes 15 minutes per device and delivers measurable improvements in both latency and range. The ExpressLRS team has once again raised the bar for open-source RC links.