Radio Transmitter
🟢 Start — zero knowledge, plain words. 🟡 Hands-on — building or buying, specifics and tradeoffs. 🔴 Advanced — the physics and math behind it.
🟢 Start. The radio is the one piece of hardware you will use every single session for years — in the simulator, at the field, on every build you'll ever own. Today's standard is an EdgeTX radio with a built-in ExpressLRS transmitter. It talks to the receiver on the drone, and to your computer as a USB joystick — which is why the site's first-30-days plan says to fly the simulator on your radio, not on a gamepad: the muscle memory is the whole point.
At a glance
| Form factor | Feel | Best for |
|---|---|---|
| Full-size | Pinch or thumb grip, room for switches | The safe default; grows with you |
| Gamepad-style compact | Thumbs, travel-friendly | Small hands, portability, sim-heavy use |
| Module-bay radios | Any of the above + a bay | Running Crossfire/ELRS at higher power later |
| Gimbal type | What it means |
|---|---|
| Potentiometer | Wears over years, fine to start |
| Hall-effect | Magnetic, no contact wear — worth having |
| Full-size vs mini gimbals | Bigger throws = finer resolution for the same thumb motion |
🟡 Hands-on. The settings that matter before anything flies:
- The arm switch is a safety interlock, not a convenience. Put arming on a two-position switch you cannot hit by accident, nowhere near switches you toggle in flight (Module 0 calls arming the most important interlock on the aircraft).
- Model match: ELRS can bind receiver-to-model so the RX only accepts its model's commands — protects you from arming the wrong quad at a busy bench.
- One model per aircraft in EdgeTX, named clearly. Rates, switches and failsafe behaviour are per-model; a shared "everything" model is how mistakes propagate between builds.
- Calibrate throws and endpoints once, in EdgeTX, then leave the firmware side at 1000–2000 µs defaults — double-scaling in both places is a classic source of "my quad flies weird".
- Radio battery: most run on 18650 cells or a 2S pack — the same charging discipline applies, just gentler.
🔴 Advanced. Two numbers connect the radio to the physics chapters:
- Latency: the radio's mixer cycle contributes ~5–10 ms — the largest electronic hop in the control chain until the motors' own mechanical ~10–30 ms (Module 0 tabulates the whole chain). A radio running slow mixer firmware costs more latency than your entire ELRS link.
- TX power: ELRS internals typically span 25 mW–1 W. More power = more link margin (Module 1), but the law caps it — in the EU the 2.4 GHz control link is generally limited to 100 mW EIRP, and the antenna's gain counts toward that (Module 13). Range problems are almost never solved by power anyway: sensitivity (packet rate) and antennas buy far more, dB for dB — the receiver page has the numbers.
⚠️ Common mistakes
- Learning the simulator on a gamepad. The hours don't transfer; radio hours do.
- Arming on a momentary switch, or next to your rates/turtle-mode switch.
- Skipping model match, then arming the wrong quad on a bench with three powered.
- Range-testing at 25 mW and forgetting to set power back before a long flight.
- Buying into a niche link ecosystem when every receiver you'll own is ELRS.
- Treating the radio as an accessory. It outlives every drone you will build — buy once.
Where this connects
- Radio Receiver — the other end of the link: packet rates, sensitivity, failsafe
- Module 1 — Radio & links — link budget: where TX power actually sits among the levers
- Module 0 — Foundations — the latency chain and the EdgeTX layer of the open-source stack
- Module 13 — Rules & spectrum — transmitter power limits, by band
Image ideas
🖼️ Photos: your own radio with the arm switch labelled and a finger on it; EdgeTX model-select screen with clearly named models; the same radio plugged into a laptop running a simulator.