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What are a RC Transmitter and Receiver?
Time:2018-05-25

What are a RC Transmitter and Receiver?

A radio transmitter (a.k.a. TX) is a device that allows the pilots to control the aircraft wirelessly. The signal/commands are then received by
a radio receiver (RX) which is connected to a flight controller.

If you are new and interested in flying drones, you should check out the beginner guide to mini quad racing.

Channels

I think the term “channels” is wrong term, we should really call it “the number of controls”.

The number of channels determines how many individual aux functions and control you can configure in the TX.

For example, throttle, yaw (rotating right and left), pitch (lean forward and backward), and roll (roll left and right), each takes up 1 channel. And so as you can see, four channels is the bare minimum to control a quadcopter (pitch, roll, throttle, yaw).
 

Additional channels on a transmitter are often called AUX channels (Auxiliary), in the form of switches and pots (potentiometer or knob). You can use them to change flight modes or trigger certain function/features on the multirotor.

In general it is recommended to have at least 5 or 6 channels for a quadcopter. The extra 1 or 2 channels can be used to arm the quad and/or switch between different flight modes.

5-channel-transmitter-diagram

Radio transmitters with more channels (6+) are generally more expensive. They tend to have better build quality and are more functional than a basic 4 or 5 channel radio transmitter.

The stick control on a radios TX is called a gimbal. (don’t get confused with camera gimbal :D )

radio controller gimbal - transmitter RC

But for hobby grade quadcopters, you definitely want more channels and controls.

Additional channels on a transmitter are often called AUX channels (Auxiliary), in the form of switches and pots (potentiometer or knob). You can use them to change flight modes or trigger certain function/features on the multirotor.

In general it is recommended to have at least 5 or 6 channels for a quadcopter. The extra 1 or 2 channels can be used to arm the quad and/or switch between different flight modes.

5-channel-transmitter-diagram

Radio transmitters with more channels (6+) are generally more expensive. They tend to have better build quality and are more functional than a basic 4 or 5 channel radio transmitter.

The stick control on a radios TX is called a gimbal. (don’t get confused with camera gimbal :D )

radio controller gimbal - transmitter RC

Modes

There are 4 different TX modes – mode 1, mode 2, mode 3 and mode 4. These are basically the different configuration of the 2 control sticks.

Mode one configuration has the elevator control on the left joystick and the throttle on the right one.

Mode two is the most common for quadcopter because the stick represents the movement of your quadcopter. It has the elevator control on the right joystick and the motor throttle on the left one. The right joystick self centres in the both axis, whereas the left joystick only self centres in yaw axis (left/right direction) and clicks or slides in the throttle (up/down) axis in order to allow constant throttle.

stickmodes

Mode three – same as Mode one except Aileron and Rudder are swapped.

Mode four – same as Mode two except Aileron and Rudder are swapped.

how to choose RC radio transmitter tx mode 3 4

Because of the identical gimbals configuration, in some TX, Mode 1 and Mode 3 are exchangeable, so as Mode 2 and Mode 4. This is achieved by swapping Aileron (roll) and Rudder (yaw) channels in user settings.

 

There is no right or wrong which one to use, just what you are more comfortable with. If you don’t know which mode to use, just go for mode 2 since majority of the pilots are using it, and it’s going to have a higher resell value later on.

Because of the identical gimbals configuration, in some TX, Mode 1 and Mode 3 are exchangeable, so as Mode 2 and Mode 4. This is achieved by swapping Aileron (roll) and Rudder (yaw) channels in user settings.

There is no right or wrong which one to use, just what you are more comfortable with. If you don’t know which mode to use, just go for mode 2 since majority of the pilots are using it, and it’s going to have a higher resell value later on.

Frequency and Technology

The most common frequency for RC is 2.4GHz. Lower frequencies are available for longer range such as 433MHz and 900MHz.

The higher frequency of 2.4GHz offers also has the advantage of smaller antenna which is much more portable. However the range is shorter than the lower frequency.

The 2.4GHz system is a much newer technology. It’s become the standard for radio control after new protocols were created that introduced frequency hopping technology. It basically looks for available channel automatically and avoid interfering with other pilots.

 

All the radio transmitter manufacturers switched to the new channel hopping protocols which made RC very easy to maintain and use. The software running is constantly scanning for the best frequency to use and if it detects any interference, automatically switches to another available channel. It is doing this many times per second so you never experience glitches or radio interference which was a big problem in the RC industry for many years. Another good thing about channel hopping is that you can fly with many other people at the same time without getting interference.

Radio Receivers

A radio controller usually comes with a receiver (RX). It’s important to know that a TX normally only works with radio receiver (aka RX) from the same brand. For example, a Frsky Taranis TX won’t work with a Spektrum receiver.

When you buy a TX, you need to realize that you are also locking yourself into their receivers. This becomes an important consideration: some brands of receivers are more expensive than others; some brands might have a better selection of light weight receivers for mini quad; Some brands don’t do telemetry….

Remember, you are going to put a receiver in every quad you build so this adds up quickly in the long run.





 
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