This part of our tutorial will be a kind of nested series and will gradually cover all the components of the quadcopter so that you have a comprehensive overview of what each component in the entire system does, how it works, and why to use this one and not another.
Transmitter and Receiver
In this chapter we will explain some basic concepts and principles. First of all, let’s talk about radio modes. These define how the sticks on your transmitter control the drone.
| Estonian | English | Function |
|---|---|---|
| Gaas | Throttle | Increases the speed of all motors |
| Kõrgus | Pitch / Elevator | Tilts the drone forward and backward |
| Tiivad | Roll / Aileron | Tilts the drone left and right |
| Rool | Yaw / Rudder | Rotates the drone around its vertical axis |
Most Commonly Used Modes
- Mode 1: Throttle on the right stick
- Mode 2: Throttle on the left stick (most common for FPV)
Most radios allow you to switch modes by adjusting internal screws.
Choosing a Radio
You need at least 4 channels: throttle, pitch, roll, yaw.
Additional channels are used for flight modes, LED control, or disarming.
Look for radios with toggle switches and potentiometers for extra functions.
RTF vs. Universal Radios
- RTF (Ready to Fly) sets include everything, but radios may be limited to that model.
- Universal radios (e.g. Radiomaster TX16S, FrSky Q X7) can be used with many drones and support multiple protocols.
External Modules
Advanced radios support external transmitter modules (e.g. Crossfire, ExpressLRS) for better range and lower latency.
Some radios have these modules built-in.
Receivers
Receivers vary by channel count and protocol.
- PWM: one wire per channel (outdated)
- PPM: multiple channels over one wire (slower)
- Serial protocols (recommended):
- FrSky/Futaba: SBUS
- FlySky: iBUS
- Crossfire/ELRS: CRSF
Binding and Range Test
To use a receiver, it must be bound to the radio.
This creates a unique link between them.
After binding, perform a range test by reducing radio power and checking signal strength at distance.
Failsafe
In binding, we outlined the loss of signal. What happens to the model then?
If you don’t have an autopilot with GPS and return-to-home (RTH) functionality, the drone will simply fall or fly away.
Failsafe settings allow you to define what the drone should do when the signal is lost — for example, cut throttle or activate RTH.
For racing drones, it is strongly recommended to immediately shut off the motors to avoid injury or damage.
Incorrect failsafe settings can result in a flyaway, where the drone disappears and may never be recovered.
Failsafe Options
- Set throttle to zero
- Set all channels to neutral
- Use Return to Home (RTH) if GPS is available
- Test failsafe on the ground before flying
Simulators and Radios
A radio is often the first thing you buy.
If it supports USB or Bluetooth, you can use it with simulators to practice flying safely before ever taking off.
Be sure to check out our Radio Control System seletions!