One of the most important purchases you can make early on is your radio control (RC) transmitter. The right choice has the potential to live with you for the rest of your career in RC. On the other hand, the wrong choice can leave you investing hundreds of dollars into equipment that you will eventually want to replace. In this edition of our buyers guide series we walk you through the different radio systems on the market and what considerations you should make when purchasing yours.
How does the radio control system work?
Modern digital radio control systems work by sending data back and forth over the 2.4GHz spectrum. At the low level, their operation is remarkably similar to that of the WiFi and Bluetooth radios found in your average phone. In fact, some control systems like those packaged in professional DJI drones are exactly that – a WiFi router embedded inside of the controller that the drone connects to on power up.
When you move the sticks and switches on your transmitter radio (TX), the position of the stick or switch is digitally encoded into a numeric value. This value is then transmitted over the 2.4GHz band to the radio receiver (RX). On the RX end, this numeric value is then either passed along to the flight controller in a quadcopter or is encoded back into a signal that small linear motion devices called servos understand. These servos are what move parts of the airplane up and down, for example.
One important consideration when purchasing your first radio system is to understand that most transmitters will only work with RX’s made by the same manufacturer. Therefore, if you buy an FrSky Taranis TX, you will be stuck using FrSky receivers. Similarly, you cannot use Spektrum receivers with Futaba TX’s. There are a few exceptions to this, but you will need to do some research to be sure.
The 2.4GHz band has a few interesting properties that anyone flying RC aircraft should know and understand. First of all, it is opaque to most buildings and anything with water in it – that’d be everything from trees to animals to waterfalls. “Opaque” means that your transmissions cannot pass through these types of objects. Therefore, if you fly your drone behind a big tree far away, don’t be surprised when it drops out of the air (or flies off!). It is also the frequency used by thousands of other home electronics – notably your microwaves and WiFi router. When I turn my Taranis on inside of my house my wife always knows because internet speeds drop to zero. Watch out for that!
What factors should I look at when choosing a radio system?
The key to making the decision on what radio system you will eventually choose is understanding the features that set them apart. As a miniquad racer community site, we are going to focus on the features that are desirable to quadcopter pilots. That being said, our aircraft are surprisingly similar to RC airplanes and helicopters and the same deciding factors apply to these aircraft as well. As an RC pilot who has flown pretty much every aircraft under the sun over the last 10 years – I can tell you that my favorite racing miniquad TX is the same TX I used for all my other aircraft.
The list below is ordered in such a way that the features we feel are most important are at the top while those that are less important are nearer to the bottom.
Frankly – if you buy a radio from our list below, chances are it is going to have every feature you really need. This is why we think that the ergonomics of the radio is its most important feature. Ergonomics is a broad category describing the look, feel and design of the radio. Like the steering wheel and shifter in a great sports car, a nice radio with fantastic gimbals and a good hand feel can make a huge difference.
Unfortunately, a lot of this is in the eye of the beholder. You really need to hold the radio to get a feel for it. If you are fortunate enough to have a hobby shop nearby, you can generally play several radios to get a feel for what you like. Another option is to visit a miniquad race in your area. Most pilots in the hobby would be happy to let you hold their radios. Check out MultiGP to find a race event near you.
One other important item to discuss is the overall design of the radio. This encompasses several items, like:
- How is the antenna mounted? Is it easy to break?
- If you plan on using a neck strap – does the radio have a lanyard loop? Will the radio balance well with the lanyard?
- Does the radio have a multitude of different switches which are easy to reach with your fingers? Some switch types are 2-position, 3-position, momentary and sliders. The first 3 are all useful for quadcopters.
- Does the radio have a touchscreen or scroll wheel for programming? Radios with only buttons can be a PITA to program.
Miniquad Receiver Options
The next thing to take a look at is the receiver options for the radio system you are considering. Remember, once you buy your transmitter you will be stuck with that brand through thick and thin, unless it has an external radio module (see below). Some important considerations for receivers to be used in miniquads are:
- Size. You want as small a receiver as you can possibly buy. When it comes to radio receivers, smaller does not necessarily mean worse performance. Many of the larger receivers on the market simply will not fit in most miniquad frames.
- Serial receiver support. Connecting your RX to your flight controller using a serial bus will greatly simplify your build and improve flight performance. You’ll know if your RX supports this if it claims to support terms like “SBus”, “SRXL” and “IBUS”.
- Diversity antennae – or more than one of them. Having two antennae can greatly increase your radio range.
- Longer antennae – 2.4Ghz antennas are pretty short. For miniquad pilots this is a problem since the carbon fiber frames will block reception of radio signals. You can therefore improve your range by installing antennas that extend well above your quadcopter frame.
During your career in the RC hobby, you’ll be buying a lot of receivers. If you’re like me, you’ll eventually end up spending more money on receivers than you did on the original transmitter. For this reason, receiver cost is actually probably more important than transmitter cost. Note that for the frankly ridicuously expensive receivers on the market (like Spektrum and Futaba) – alternatives are often available from Chinese vendors. Check out the OrangeRX lineup if you are curious about this.
The radio transmitter is hands down the most expensive single component you are likely to buy when getting into the hobby. There are some budget options on the market that you can “make do” with, but for a really nice radio that will last you for the next 10 years or longer – expect to spend at least $200. Of course, there are some even better options – capping out with models like the Futaba 18MZ which comes in at a whopping $3000! The higher end models will generally come with generous warranties, advanced electronics like color touchscreen displays and extremely high quality components.
Some radio systems have the capability to transmit data from the RX back to the TX. This is referred to as telemetry. Often times, this is done to send critical flight data like the battery voltage back to the user. Programmed right, this will allow you to warn yourself whenever your battery is going dead so that you do not damage it or get forced to land far away.
Telemetry data can be obtained in a variety of ways. One way is to purchase external sensors which measure some data, like battery voltage, and send it back down to your transmitter. These sensors can be bulky and heavy and are generally not used in lightweight miniquad racers. Another option is to have your flight controller talk to your RX. In this scenario, the flight controller can do the voltage detection – most can – and will send the data it observes down to your TX. The problem is not all flight controllers support all telemetry systems. As a matter of fact, as of December 2016 only FrSky telemetry is supported by Betaflight – our favorite flight control software.
In the end, we think the value of telemetry is in the eyes of the user. We have friends who cannot live without it, while your friendly editors at Propwashed much prefer to have flight data shown on the video feed using an on screen display (OSD).
Frequency and Range
Every radio we are familiar with on the market operates on the 2.4GHz frequency spectrum. That being said, there are modules or modifications available for many transmitters that allow you to transmit on 1.3GHz, 900MHz and 433MHz. As you use lower frequencies to communicate with your model, your radio control system’s range drastically improves. This is because lower frequency transmissions can travel further without as much disappation and are also because these frequencies are better able to pass through obstacles like trees and houses.
Not all 2.4GHz radios have the same range either. Unfortunately, comparing the range between two different radio systems is pretty difficult. The reason is there is no “spec” you can really look at to determine this information. It is mostly determined by the type and orientation of antennae found in both the Transmitter and the Receiver, and in the output power of the transmitter. The transmitting power for any given radio system can generally be found with some googling, but we caution you against using it as the end all be all of determining the range of your system.
Ultimately, if getting the best possible range is a consideration for you, we recommend purchasing a transmitter with an external RF module bay so that you can use some of the aftermarket low-frequency TX modules.
External RF Module Support
An external RF module is a plastic box that hooks into the back of your transmitter, allowing it to transmit on frequencies and bands that are not standard for that TX. It is in this way that you can modify an FrSky Taranis to talk to Spektrum receivers, for example. It also allows your radio to transmit on lower or higher frequencies and take advantage of the greater range of these frequencies. Please note that if you use an external RF module, you’ll need to purchase the appropriate receivers that pair with that RF module. Having an external RF slot is like having the ability to buy a whole new radio system on the cheap.
You’ll know if a radio supports an external RF module because it will have a bay in the back of the transmitter where you can dock the rectangular module. There are several different types of modules but the “JR” style module is the most popular these days – available on JR transmitters as well as FrSky offerings.
Trainer Port and Compatibility
A trainer port is a plug on your radio that lets you pair two radios together so that they are controlling the same module. The idea is you have an instructor and a student, each with their own radio. The instructor will flip a switch to transfer control between his radio and his student’s radio. Thus, he can fly a quadcopter to safe height and location, transfer control to the student, then take control back if the student ever gets close to crashing.
Flying with an experienced pilot in this manner is a great way to train. It’s also a ton of fun to get a second transmitter and train your friends and family how to fly once you get good. For this reason, we really like radios with built in trainer ports which support this kind of flying.
If a trainer port is something that interests you, make sure you are aware of trainer compatibility between radios. Generally two of the same radio will have no problem talking to each other – but that is not always true of different brands. Some quick Googling will generally be able to get you this information.
Transmitter Internal Battery
There are three types of battery systems used in RC transmitters:
- Standard replaceable batteries – often AA sized. The advantage of using these types of batteries is that it is easy to carry a spare set with you – you’ll hardly ever get stuck at the field with a dead transmitter and no way to fly. The problem is it can get expensive to keep replacing the batteries, depending on how much you fly. As with other replaceable batteries, you can opt to use rechargeable variants to get around this.
- NiCd or NiMH batteries. You’ll know if your radio has these because the batteries will have a very distinctive shape – like a bunch of cylinders wrapped in plastic. These batteries are rechargeable but do not have a huge capacity. They also have “memory” problems where they will slowly lose their capacity over time and need replacement. Thankfully, they are generally pretty cheap.
- LiPo batteries. These use a low-power variant of the lithium batteries you use in your multicopter. Like the ones in your aircraft, these batteries have very high energy density and a single charge will last for up to a hundred hours of continuous use in some radios. They also last practically forever since radios do not stress them. These are definitely the “best” types of batteries in radios in our opinion.
The number of “channels” advertised by most radio manufacturers refers to how many individual servos or motors your radio can control at once. Channel count was the main selling point between high end and low end radios for a long time in the RC hobby’s history. Back in the “old days” of analog radios, adding new channels was actually quite technically difficult. These days, channel count is mostly a marketing gimmick. The only thing really preventing you from adding more channels these days is how many switches and knobs you can add to your radio – and it all starts getting redundant / useless pretty quick.
You only really need 5 channels to have a fantastic flying experience with a racing miniquad. In our opinion, 6 channels is the real sweet spot though. If you are interested in flying complex airplanes or helicopters, you’ll probably want to look at radios that offer at least 8 channels. We really don’t understand the reason why you would want more than 8 though – so don’t drop 3 grand on a 24 channel radio unless you know exactly why you need it.
Recommended Radio Systems
FlySky FS-i6 Radio System – $44 at Gearbest
FlySky offers one of the best budget radios on the market with it’s FS-i6 radio system coming in under $50 in many online shops. We reviewed this system here.
FrSky – Propwashed Recommended Pick
FrSky is the manufacturer of the famous Taranis transmitter. When the Taranis came to market, it blew everyone away with it’s huge feature set and great performance for what was then a very reasonable price. These days there are competitors on the market at a fraction of the price of the Taranis which offer similar features. We think the Taranis is the best all-around transmitter, though, because of it’s broad support across the community. FrSky recently came out with a higher-end radio system that uses the same receivers as the Taranis called the Horus. This system has been met with mixed reviews but looks to be a good option for those looking for a higher end radio using FrSky components.
Futaba 8J – $240 at Amazon
Futaba is an “old guard” in the radio system arena. A 72MHz Futaba system was the first computer radio I ever purchased and for that reason the company has always been dear to my heart. Their radios have fantastic build quality and a great warranty and customer service to go with them. However, all Futaba gear is pretty pricey.
RadioLink AT9 – $93 at Banggood
RadioLink has a line of very nice looking radio systems. I have spoken to several people who use their systems who have nothing but great things to say. They are not the cheapest transmitters on the market, but their build quality and featureset is aimed more at the mid-level market like the Taranis – while coming in at half the price.
Spektrum was one of the first companies to release an all digital radio using the 2.4GHz spectrum a long time ago. Since then, they’ve matured their line-up to become the most popular radio manufacturer around for airborne R/C. They haven’t quite caught on as well with the miniquad racer crowd due to the initial lack of good receiver options, high prices and a scandal involving false advertising on how their spread spectrum system worked. Nevertheless – they make fantastic quality radios and their programming user interface is, in my opinion, unparalleled. My DX18 has been my favorite radio for a long time now.
Team Black Sheep
TBS Tango – $250 at TBS’ Online Store
Team Black Sheep, or TBS, recently released the Tango transmitter onto the market. This transmitter is aimed squarely at the FPV racer community with a built in FPV video receiver and monitor. This is another radio system we haven’t personally used (yet), but have heard great things about.
HobbyKing’s brand, Turnigy, has turned out several radios over the years. The most pertinent ones are the 9X and the Turnigy i6. Of these, we highly recommend the i6 – it is the exact same radio as the FlySky i6, which we found to be a fantastic multirotor radio for the price. We are less enthused with the 9X – which all but requires a separate radio module to be usable for miniquad racing. Both radios have great support from the community.
Like many of our articles, many of the links above are affiliate links. We urge you to shop around, but if you do decide to buy from the vendors above, we would really appreciate it. It doesn’t cost you a dime more, but it sends us a few cents every time a purchase is made. Thanks!