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Your radio link is the invisible cable between your thumbs and your drone. When it’s good, you never think about it. When it fails, the drone is no longer yours to control. That’s why the radio is the one part worth buying carefully from the start.
How a radio link works
Your transmitter (TX) reads your sticks and switches and sends that data many times per second to the receiver (RX) on the drone. The receiver passes it to the flight controller over a serial protocol. Many links also send telemetry back: battery voltage, link quality and GPS position on your radio’s screen.
Why ExpressLRS took over
ExpressLRS (ELRS) is an open-source radio system that became the default for FPV because it offers:
- Very low latency at high packet rates for racing.
- Long range at lower packet rates.
- Cheap, tiny receivers.
- Hardware from many brands that all work together.
TBS Crossfire, another long-range system, remains popular, especially on 900 MHz. Other systems are still used on ready-to-fly drones.
2.4 GHz vs 900 MHz
| Band | Strengths | Trade-offs |
|---|---|---|
| 2.4 GHz | Small antennas, high packet rates, very common | Slightly less penetration through trees and terrain |
| 900 MHz (915 MHz in the U.S.) | Better penetration and range | Larger antennas, lower maximum packet rates |
For most freestyle, racing and legal line-of-sight long range, 2.4 GHz ELRS is plenty.
Packet rate and range
Packet rate is how many updates per second the link sends.
- High packet rates (250 Hz–1000 Hz): lowest latency for racing and freestyle, a bit less range.
- Lower packet rates (50–150 Hz): more sensitivity and range for long-range cruising.
Link quality (LQ) and RSSI on your OSD tell you how healthy the link is. Watch for LQ dropping as you fly farther.
Binding with a binding phrase
ELRS uses a binding phrase instead of a button press:
- Flash your TX module and RX with the same ELRS major version and the same binding phrase, using the ExpressLRS Configurator or the device’s Wi-Fi page.
- Power both. The receiver LED turns solid when connected.
- In Betaflight, set the receiver to Serial-based, CRSF protocol, on the correct UART.
Antenna placement
- Keep receiver antennas away from carbon fiber, which blocks radio signals.
- Mount two antennas (on diversity receivers) at 90 degrees to each other.
- Keep the active element (the last few centimeters) clear of the frame and props.
- Point your transmitter antenna’s side, not its tip, toward the drone.
Failsafe: decide what happens when the link drops
Set failsafe in Betaflight or ArduPilot before your first flight:
- Freestyle in open fields: “Drop” (motors stop).
- Long range with GPS: GPS Rescue or RTL.
See redundancy and failsafes for building in backup links.
Choosing a radio transmitter
- Gimbals: hall-effect gimbals last longer than potentiometer gimbals.
- Size: full-size or compact gamepad style; try both if you can.
- Internal ELRS module or an external module bay.
- EdgeTX firmware for flexible setup.
Shop ELRS radios · Shop ELRS receivers
Understanding link quality (LQ) and RSSI
- LQ (link quality): the percentage of packets that arrive successfully. 100% is perfect. Drops below about 70% are a warning sign; very low values mean the link is close to failing.
- RSSI: received signal strength, usually in dBm. Values closer to zero are stronger. The weakest usable signal depends on your packet rate.
Watch both. LQ tells you whether commands are getting through; RSSI tells you how much margin you have left.
Transmitter power settings
ExpressLRS transmitters let you set output power. Higher power improves range in difficult conditions, but drains the radio’s battery faster and makes the module warm. Dynamic power raises power only when the link needs it, a good default for most pilots. Follow your local radio regulations.
Model match and setup tips
- Model match prevents flying one drone with another model’s settings. Enable it once each drone has its own model in your radio.
- Separate models on your radio for each drone, with matching rates and switch setups.
- Label switches with the same function on every model. Arm should always be on the same switch.
Common radio link problems
| Symptom | Likely cause | Fix |
|---|---|---|
| Won’t bind | Version or phrase mismatch | Reflash both with the same version and phrase |
| Short range | Antenna damaged or blocked by carbon | Replace or reposition antenna |
| Random failsafes | Loose wire, brownout, interference | Check wiring and power, reposition receiver |
| Latency feels high | Low packet rate | Raise packet rate for freestyle |
Frequently Asked Questions
What is ExpressLRS?
An open-source radio control system known for low latency, long range and inexpensive receivers. It’s now the most common radio link in FPV.
Is 2.4 GHz or 900 MHz better for FPV?
2.4 GHz is common and has small antennas and high packet rates. 900 MHz offers better penetration and range, which helps long-range pilots.
Why does my ExpressLRS receiver not bind?
The most common cause is a mismatched binding phrase or firmware version between transmitter and receiver. Flash both with the same version and phrase.
What packet rate should I use on ELRS?
250–500 Hz is popular for freestyle and racing. Lower rates such as 50–150 Hz give more range for long-range flying.