What is ELRS?

Your drone needs two invisible connections: one carries the picture down to your goggles (that's the video system), and one carries your steering up from the controller. ELRS is the steering one.

When you move the sticks, your controller whispers to the drone many times every second: "a little left… now up…" ELRS is the language they whisper in. It's popular because it almost never loses its voice — even far away or with lots of walls in between.

ExpressLRS (ELRS) is the open-source 2.4GHz control link that has become the default for whoops. Your radio contains an ELRS transmitter; the whoop has an ELRS receiver built into its flight-controller board — that's what "BNF, ELRS" means on a listing: bind and fly, no receiver to install.

What you need to know

• Any ELRS 2.4GHz radio works — popular picks include the RadioMaster Pocket, Zorro, and Boxer lines. One radio, whole fleet.
• Binding uses a "bind phrase" — set the same phrase in your radio and (for most whoops) in Betaflight, and they find each other automatically.
• Firmware versions matter: your radio's ELRS version and the drone's receiver version need to be compatible (v3-to-v3 is today's normal). A brand-new radio with a very old whoop — or the reverse — is the classic can't-bind headache.
• ELRS is not the video link — a DJI O4 whoop with ELRS still needs DJI goggles; an HDZero whoop with ELRS needs HDZero goggles.

Competitively, ELRS won on link reliability and latency at low power — solid control at packet rates from 250Hz up, with range headroom that whoop distances never test.

• Packet rate: most whoop receivers run 250–500Hz. Higher rates trim control latency a few milliseconds; consistency matters more than the number.
• SPI vs UART matters for racing: SPI-integrated receivers (many ultralight builds) are capped around 500Hz and frozen at the firmware baked into Betaflight; UART receivers run real ExpressLRS firmware, update independently, and unlock the highest rates. Check the spec table on any model page here — we list which one you're getting.
• Race etiquette: events pin everyone to agreed power (usually 25–100mW) and firmware versions so binds are predictable at the gate.
• Telemetry (link quality, RSSI, battery voltage back to the radio) is your early-warning system — set a link-quality alarm before you trust a new spot.

ExpressLRS is an open-source LoRa-based control link built on Semtech SX128x-series 2.4GHz transceivers, using LoRa modulation at low packet rates for range and FLRC at high rates for latency. The over-the-wire protocol into the flight controller is CRSF.

• Bind phrase → UID: the human-readable phrase hashes to the UID that both ends share; no button-press pairing state to lose.
• SPI implementation: on ultralight AIO boards the radio chip hangs off the FC's SPI bus and the ELRS protocol logic lives inside Betaflight itself — cheap and light, but protocol-frozen to whatever Betaflight ships (effectively ELRS v3.0 semantics, ≤500Hz) and not flashable via the ExpressLRS toolchain.
• UART implementation: a discrete receiver MCU runs genuine ExpressLRS firmware, talks CRSF over a UART, updates over Wi-Fi, and tracks upstream releases (1kHz modes, telemetry ratio control, Gemini diversity on supporting hardware).
• Regulatory posture: 2.4GHz ISM band, frequency-hopping, transmit power configurable — the whoop-class norm is 25–100mW, far under the band's ceilings in most jurisdictions.