A radio control system is made up of two elements, the transmitter you hold in your hands and the receiver you put inside your drone. Dramatically simplifying things here, your drone transmitter will read your stick inputs and send them through the air to your receiver in near real-time. Once the receiver has this information it passes it on to your drone’s flight controller which makes the drone move accordingly.
FREQUENCY AND CHANNELS
Radio will have four separate channels for each direction on the sticks along with some extra ones for any auxiliary switches it may have.
Thankfully frequency and channel-wise radio controls are a lot smarter than their FPV counterparts and are much easier to manage. Video transmitters and receivers for example both require setting to the correct channel along with diligent channel management every time you fly. A Radio Controller however simply needs to bind or pair with an RC radio receiver when it’s first set up.
From then on it will always link and hop over various frequencies in the 2.4Ghz band to ensure a solid link with theoretically hundreds of pilots operating at the same time.
The limit of range is normally where the receiver can no longer clearly hear what the transmitter telling it and typically falls in the 1km range in normal conditions. Imagine trying to talk to someone across a field The range of your radio link will be dependent on a few factors:
- The output power of your transmitter – Many run just below the legal maximum to be compliant with international standards.
- The sensitivity of the Receiver – A more sensitive receiver is like having better hearing, the signal will travel further however it may pickup more noise in certain conditions
- The quality of your antennas at both ends – Antennas could be an entire article on their own but basically a larger antenna will send and receive a better signal. Often optimizing your antenna placement will make a huge difference to the performance to the system.
COMPARABILITY AND COMMUNICATION PROTOCOLS
Different radios speak their own languages to talk their receivers with some being faster and others being more reliable or even smaller/cheaper. This means that you must use a receiver that is compatible with your transmitter which will most likely be made by the same company.
Once the receiver has the signal it needs to communicate it to the flight controller. Different radios have different protocols for this and it is important to make sure that your flight controller and software supports it. The speed of this communication is important as it could introduce a delay into your system if too slow
Some standard protocols include
PWM – This is your classic analog signal with one separate wire for each channel. This is now slow and outraging and should be avoided if possible
PPM – This is a slightly improved version of PWM where all the channels are sent over one wire as a series of timed pulses. This is quicker than PWM however is still not the best option.
Digital Protocols (SBUS, IBUS, DSM2/X) – Instead of relying on the timings of different pulse widths digital signals send numbers in ones and zeros which gives perfect accuracy along with even quicker response times.
For the speed and precision required to fly a mini quad you should always try to use a digital protocol with the variant being dependent on your radio’s manufacturer.
FACTORS TO CONSIDER
With all this in mind lets take a look at what you should consider when choosing a radio and receiver combo whilst comparing some of the options out there.
If you have looked at some radios online you may of noticed that many give you an option to choose a different mode (eg Mode 1,2,3 or 4). These modes represent which stick does what for example which stick is the throttle.
The most common mode for mini quad pilots is mode 2 with the throttle on the left and I would suggest that you stick with this unless you have prior experience with other modes.
Once you adapt to a particular mode it will be challenging for your muscles and brain to switch! If you do go for a more exotic mode don’t worry, it’s a preference for you and won’t affect anything else. Many radios allow you to open up the gimbals and switch modes at your leisure.
The gimbals are the sticks that you use to control your mini quad. For mode two pilots you will have one on the left controlling throttle and yaw leaving pitch and roll to the right-hand gimbal.
Good gimbals can be adjusted for size, and tension and can have customizable stick ends. Some gimbals have better quality sensors such as hall sensors.
These rely on magnets instead of a brushed joint which gives a much smoother feel and a more precise flight experience.
Pinch or Thumbs?
The gimbals on a transmitter are much longer than an Xbox or Playstation controller and there is no right or wrong way to hold them.
Typical options include pinching the sticks between your index finger or thumb or by just using your thumb on it’s own. In general whatever radio you choose you should read some reviews to check if they are pinch or thumb friendly.
Thumbers typically want shorter sticks and a narrower radio so that they can grip the back.
A pincher will want longer travel but will have to beware of any potential switches they could knock by accident. They may also require a neck strap.
Transmitters don’t just have gimbals, they typically have an array of switches you can use for arming and changing flight modes etc.
Switches come in two or three-position forms as well as sliders however as mini quad pilots we don’t really need too many compared with aircraft flyers or our photography friends.
I would suggest having a radio with four configurable switches that will cover everything you could ever need.
Speaking of switches each one will require it’s own channel and the gimbals require two (each one for each direction). That means a six channel radio will only let you use the gimbals and two switches even if it has more. Higher end radios will give you up to 16 channels which is more than you can ever need. If you are planning anything special make sure you have enough channels free to make it all possible.
So far we have covered how the radio talks to the quad but some quads can actually talk back relaying important information such as battery voltage and signal strength. This information can either be displayed on a screen or read out by audibly by the remote to warn you when to land or when you are out of range. Having this read out audibly to you is great as you can focus on flying and won’t miss any warnings which could cause you to crash or lose a quad.
The more intelligent transmitters are extremely powerful allowing your radio to do whatever you imagine. Any radio running Open Tx is highly programmable with logical switches and special functions. Here are a few examples of what can be achieved besides playing snake on the radio:
- Want to put your own splash screen and run custom sound effects? Easy
- Want your radio to register how long your quad is inverted and count it out for you? Sure
- Use your RF signal to track laps. No Problem
- Use Telemetry to speak to your flight controller and adjust the PIDs and filters in flight. Yup
If you are looking for something that really can do anything and are willing to put the time in you can’t go wrong here!
Many radios come with an external module bay which allows you to place a large array of standard RC-sized modules in a completely different radio.
Multiprotocol modules are also available which allow one radio to control nearly everything including toy drones with their own remotes.
High-end radios will have built-in Li-ion batteries with a built-in charging circuit allowing you to charge your radio with a simple DC jack. These typically will last for days before they need charging and is most people’s preferred option.
The cheaper radios on the other hand may not come with batteries at all and run on AA batteries. This is something worth considering when buying a budget radio is it may cost you more than you’d expect in the long run.
The only advantage to this type of battery is that they are readily available and can be swapped with little downtime. In the middle, is your category of radios that can run off lipo batteries but they will require you to charge them separately.
On the plus side, you get a long battery life at a low cost however you also have to source, charge and manage a lipo yourself. Some radios may also come with NiMH batteries which will not last as long.
Talking about batteries brings us onto mods nicely. If you were to go to a race or just a meetup for experienced pilots you may notice that none of them are running stock transmitters. Many users in the FPV community mod their transmitters to meet their specific requirements whether that be functionally or aesthetically.
My personal radio has a slot for 18650 Li-ion batteries, upgraded gimbals, larger stick ends, and aesthetic touch-ups to the switches and antennas.
The basic FlySky i6 can be modified to have 10 channels IBUS with even a voltage alarm with some basic solder skills.
Many common mods include:
- Antenna mods to increase range
- Battery mods to increase life or improve charging
- Switch and Gimbal mods to improve the feel
- Aesthetic mods such as paint or hydro dipping give a custom look
- Module mods to support alternative protocols
- Grips/stands for support
- Software mods for added functionality
As your radio is another component you can’t crash (unless you drop it!) I would suggest spending a reasonable amount of money on one. Features like telemetry could literally make the difference between losing a quad or draining the battery too far which could save you a small fortune. Typically pilots use a remote for years where a new quad could be completely destroyed after a few months.
If budget really is a factor then you do still have some solid options and they will in no way stop you from having a great FPV experience! If you do choose to upgrade in the future bear in mind that you will have to change all of your receivers which could cost you a small fortune.