Radio Protocol 101: The Only Guide You Need

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Blog cover: FPV drone radio link protocols

Are you a quadcopter enthusiast or an FPV (First Person View) pilot looking to delve into the world of radio protocols?

Understanding FPV radio protocols is essential for establishing a reliable and efficient RC control link between your transmitter and drone.

In this article, we’ll explore the ins and outs of radio protocols, discuss popular options, and help you choose the right one for your needs.

TL;DR: FPV Control Protocol Comparison Chart

Here is a quick cheat sheet comparing the major specifications of each protocol:

ProtocolFrequencyLatencyUpdate RateRangeOutput PowerPrice
FrSky ACCST2.4GHz18ms150Hz1-2km100mWCheap
FrSky ACCESS2.4GHz9ms150Hz1-2km100mWModerate
TBS Crossfire900MHz11ms150Hz10-100kmUp to 2WExpensive
TBS Tracer2.4GHz4-7ms250Hz1-20kmUp to 1WExpensive
ImmersionRC Ghost2.4GHz8-12ms30-250Hz2-15kmUp to 350mWModerate
ExpressLRS900/2.4GHz4-7ms150-500Hz10km+Up to 1WModerate/Expensive

What is an FPV Control Protocol?

The control link allows the transmitter you hold in your hands (also called the radio controller) to communicate with the drone wirelessly.

When you move the sticks on your radio, it sends signals to the receiver on the drone. The receiver then passes those signals to the flight controller, which adjusts the motors and enables you to fly.

Different components use different protocols, so some components, like the receiver and the flight controller, have to be bilingual – they “listen” in one language (input) and “speak” in another language (output).

This image from oscarliang illustrates their relationship quite clearly.

Rc Radio Transmitter Receiver Protocol Tx Rx Esc Fc Communication Signal

The control protocol determines factors like:

  • Frequency band – Most protocols use either 2.4GHz or 900MHz. Higher frequencies allow for more bandwidth while lower frequencies provide longer range.
  • Latency – The time delay between moving the sticks on your radio and the drone responding. Lower latency provides a more real-time, immersive flying experience.
  • Update rate – How many times per second the control data is transmitted. Faster updates mean lower latency.
  • Range – The maximum distance your control link can reliably function. More range provides more confidence and flexibility when flying far out.
  • Reliability – How resistant the link is to interference so you don’t experience control dropouts a.k.a. fail-safes.
  • Features – Other fancy capabilities like telemetry, onboard DVR recording, adjustable output power, etc.

We’ll examine all of these factors for the major protocols below. But first, let’s go over some terminology around radio transmitters and receivers.

Radio Transmitter and Receiver Basics

There are a few key specs to be aware of when it comes to radio transmitters and receivers:

  • Frequency band – As mentioned above, most FPV control protocols operate on either 2.4GHz or 900MHz frequency bands.
    • 2.4GHz provides more bandwidth, allowing for faster data rates and lower latency. But it has shorter range and is more vulnerable to interference from other 2.4GHz sources like WiFi.
    • 900MHz offers much longer range, but less bandwidth. The lower frequency means it can better penetrate obstacles. But there’s greater risk of interference between pilots when flying in groups.
  • Channel width – The amount of spectrum occupied by the signal. Wider channels allow for faster data rates at the cost of being more susceptible to interference. Channel widths are typically 5MHz, 10MHz or 20MHz.
  • Modulation – The encoding scheme used to transmit the data. Common types are FSK (frequency shift keying) and LoRa (long range). FSK provides lower latency while LoRa allows for longer range. Some protocols support multiple modulations.
  • RF output power – The amount of power the transmitter outputs, measured in milliwatts (mW) or Watts (W). More power increases range but uses more battery and increases interference. 100-1000mW is typical for FPV.

Now let’s dive into the specific control protocols available and see how they differ.

List of Popular RC Protocols for FPV

FrSky ACCST

FrSky ACCST (Advanced Communication Control System Technology) is the most popular FPV control protocol on the market today. It’s included on pretty much all ready-to-fly racing drones and supported on most radio transmitters aimed at FPV pilots.

FrSky ACCST Specs

  • Frequency band – 2.4GHz
  • Channel width – 2MHz
  • Modulation – Proprietary FSK
  • Update rate – Up to 150Hz
  • Output power – Up to 100mW
  • Latency – 18ms
  • Range – 1-2km

FrSky ACCST Pros

  • Ubiquity – It’s nearly universal on FPV quads and radios, providing full compatibility.
  • Price – ACCST receivers and modules are very affordable, often the cheapest option.
  • Size – With small 2.4GHz antennas, ACCST hardware is compact and lightweight.

FrSky ACCST Cons

  • Limited range – 1-2km is enough for most pilots, but some long-range scenarios may push its limits.
  • Higher latency – Not the worst, but newer protocols have pushed latency down into the single digit millisecond range.
  • Firmware hassles – Identifying and flashing the correct firmware version can be frustrating.

Who Should Use FrSky ACCST?

FrSky ACCST is perfect for beginners just getting started with FPV drones. It’s simple, reliable technology that provides more than enough performance for casual flying and early racing.

The ubiquity of ACCST means it’s easy to find compatible gear, and the price is very budget friendly. For someone looking to spend the least amount to get in the air, ACCST is a great choice.

The main downside is limited range, but that only becomes a major issue if you really want to push longer distance flights. Even moderate long range is very doable with ACCST though.

Who Should Avoid FrSky ACCST?

Experienced pilots looking for top-of-the-line performance will want to consider other protocols beyond ACCST. Specifically:

  • Long-range pilots – If your goal involves routinely flying 5+ kilometers out, ACCST’s range limitations may be frustrating. Something like Crossfire or R9 will provide the confidence needed for true long distance.
  • Racers – Shaving every millisecond of latency can give you a competitive edge. ACCST’s higher latency might hold you back. Look at Ghost, Tracer, or ExpressLRS for lower lag.
  • Groups – More than 5 pilots all using ACCST can lead to interference issues. 900MHz systems handle groups better.

So in summary, ACCST is a great starting point but may leave you wanting more as your skills progress or flying goals shift. Next we’ll look at the successor protocol that improves upon ACCST’s shortcomings.

FrSky ACCESS

FrSky ACCESS was released a few years ago as the next evolution of ACCST, designed to fix a few of its limitations.

FrSky ACCESS Specs

  • Frequency band – 2.4GHz
  • Channel width – 2MHz
  • Modulation – Proprietary FSK
  • Update rate – Up to 150Hz
  • Output power – Up to 100mW
  • Latency – 9ms
  • Range – 1-2km

FrSky ACCESS Pros

  • Lower latency – Brings lag time down to 9ms vs. 18ms on ACCST.
  • OTA updates – New firmware can be wirelessly pushed to receivers without plugging into a computer. Very convenient.
  • Improved binding – Easier to pair multiple receivers and switch between models.

FrSky ACCESS Cons

  • Limited compatibility – Only works with newer FrSky radios. No support for other brands.
  • Range still limited – Slightly better than ACCST but still caps out around 2km.
  • Antenna size – Still uses small 2.4GHz antennas that are somewhat fragile.

Who Should Use FrSky ACCESS?

FrSky ACCESS makes the most sense for pilots already invested in the FrSky ecosystem looking for an upgrade from ACCST.

The improvements like lower latency and OTA updates are nice quality of life upgrades. For someone with a Taranis or Horus radio, Access is an easy drop-in module replacement.

ACCESS keeps compatibility with existing ACCST receivers. So you can switch between ACCST and ACCESS modules to suit your needs.

Who Should Avoid FrSky ACCESS?

Since ACCESS only works with FrSky radios, anyone who uses other radio brands is locked out. You’d need to switch over to a Horus or Taranis to use it.

Also, the limited 2km range means extreme long-range pilots will still want something that provides more distance.

And if you’re looking for the absolute lowest latency for racing, there are better performing options available now.

For most pilots though, ACCESS provides a solid middle ground and the convenience of OTA updates.

TBS Crossfire

Team BlackSheep Crossfire has emerged as one of the most popular long-range control protocols for FPV pilots. Its combination of excellent range, low latency, and a polished user experience has built a big following.

TBS Crossfire Specs

  • Frequency band – 900MHz
  • Channel width – 10MHz
  • Modulation – Proprietary FSK
  • Update rate – Up to 150Hz
  • Output power
    • 250mW
    • 500mW
    • 1W
    • 2W
  • Latency – 11ms
  • Range – 10-100km+ (depends on output power)

TBS Crossfire Pros

  • Long range – With high output power and excellent RF link budget, Crossfire provides basically unlimited control range for most pilots. Even smaller 250mW Crossfire setups reach several kilometers in distance.
  • Low latency – Very snappy response between sticks and drone. Great for racing and precise flying.
  • Reliability – The frequency hopping scheme makes Crossfire extremely reliable in all conditions. Failsafes are rare.
  • Easy setup – The Crossfire configurator app and OTA updates make it simple to manage.
  • Bind-N-Fly options – Some ready-to-fly drones come with Crossfire receivers installed.

TBS Crossfire Cons

  • Large antennas – The longer 900MHz antennas are more awkward to mount and more prone to damage on a mini quad.
  • Limited channels – The narrow 900MHz band means group flying sessions require coordination to avoid interference. Not optimal for races with many pilots.
  • Price – Crossfire receivers, modules, and antennas carry a significant price premium over more basic protocols.

Who Should Use TBS Crossfire?

Crossfire’s excellent combination of long range, low latency, and excellent reliability make it a top choice for:

  • Long-range and technical pilots – The essentially unlimited range envelope gives peace of mind when flying 5, 10, even 50km out. Even smaller quads gain several extra kilometers of range with Crossfire.
  • Groups – While not ideal for 30 person races, Crossfire works very well for coordinated group flights of 4-8 pilots.
  • Reliable performance – Crossfire’s frequency hopping scheme provides an extremely reliable link in all conditions short of a direct antenna strike. It just works.

So in general Crossfire is a great fit for serious pilots looking for high performance and “set it and forget it” reliability.

Who Should Avoid TBS Crossfire?

  • Racers – The limited channels on 900MHz can cause interference issues at races with many pilots in close proximity. There are better options for dedicated racers.
  • Cost-conscious shoppers – You pay a premium for Crossfire gear. If budget is a concern ACCST or Ghost provide better value.
  • ** micrographers** – The large 900MHz antennas are harder to mount cleanly on smaller quads. The 2.4GHz protocols work better for pretty cinewhoop builds.

So Crossfire is probably overkill for casual park flyers. But for pilots pushing limits with long range or technical flying, it’s a top choice.

ImmersionRC Ghost

The ImmersionRC Ghost control protocol is a newer offering that aims to provide a balance of long-range and low-latency performance. Its flexible design allows it to be tuned for different applications.

ImmersionRC Ghost Specs

  • Frequency band – 2.4GHz
  • Channel widths
    • 2MHz (long range mode)
    • 5MHz (all other modes)
  • Modulations
    • Proprietary FSK (long range mode)
    • LoRa (all other modes)
  • Update rates
    • 30Hz (long range mode)
    • 150Hz (standard mode)
    • 250Hz (“Pure Race” mode)
  • Output power
    • 25mW
    • 100mW
    • 350mW
  • Latency
    • 12ms (standard mode)
    • 8ms (“Pure Race” mode)
  • Range
    • 2km+ (standard mode)
    • 10-15km (long range mode)

ImmersionRC Ghost Pros

  • Flexible performance – With its easily adjustable modes, Ghost is tuned for long range OR low latency flying.
  • Tiny receivers – The 2.4GHz receivers are tiny and easy to integrate on a build.
  • Solid range and latency – Good all-around performance without compromises.
  • Smooth launch – Ghost has seen minimal bugs or issues since release.

ImmersionRC Ghost Cons

  • Master fire only – Ghost is compatible with Betaflight but hasn’t been integrated natively into flight controllers yet.
  • Limited RF power – At just 350mW max, hard-core long rangers may want more output.
  • Ecosystem adoption – Being brand new, very few BNF models come with Ghost yet. Market support is still growing.

Who Should Use ImmersionRC Ghost?

Ghost is a great option for pilots looking for versatility across different types of flying:

  • Flexible pilots – The ability to tune for long-range or latency gives Ghost broad appeal. You can adapt it to suit whatever type of flying you’re doing that day.
  • Sector racers – The low 8ms latency rivals the fastest protocols when in “Pure Race” mode. Very responsive.
  • Cinewhoop pilots – Ghost receivers disappear on small builds. And the 2.4GHz antennas save headaches.

So Ghost provides a nice middle ground without major compromises. It lacks theultra-refined performance of specialist systems focused purely on racing or long range, but gives you 80% of both capabilities.

Who Should Avoid ImmersionRC Ghost?

  • Cost-conscious buyers – Ghost gear costs a bit more than ACCST. Not hugely expensive but there are cheaper options.
  • BadFlighters – Since Ghost hasn’t been natively implemented into flight controllers yet, you have to run it in a Master/Slave config. This adds complexity compared to newer protocols that run as a serial link to the FC.
  • Cutting-edge racers – “Pure Race” mode is fast but Tracer and ExpressLRS still have an edge in absolute lowest latency.

TBS Tracer

TBS Tracer is Team Black Sheep’s low-latency, short-range optimised version of Crossfire, designed for high-speed racing drones. It provides silky smooth control response by focusing on speed rather than distance.

TBS Tracer Specs

  • Frequency band – 2.4GHz
  • Channel width – 10MHz
  • Modulation – Proprietary FSK
  • Update rate – Up to 250Hz
  • Output power
    • 25mW
    • 100mW
    • 1W (“Ludicrous” mode)
  • Latency – 4-7ms
  • Range
    • 1-2km (25/100mW)
    • 10-20km (Ludicrous mode)

TBS Tracer Pros

  • Extremely low latency – Tracer has the lowest latency of any major control protocol available.
  • Performance optimised for racing – Everything from the modulation to channel width is optimised purely for speed and responsiveness.
  • Crossfire compatibility – Tracer works with existing Crossfire transmitters and receiver hardware with a simple firmware update.
  • Refined experience – As an extension of Crossfire, Tracer offers the same polished and intuitive user experience.

TBS Tracer Cons

  • Limited flexibility – Tracer is built for racing only. Long range capabilities are an afterthought.
  • Output power limitations – Getting the full 20km range requires battery draining “Ludicrous” mode.
  • Ecosystem support – As a newer protocol, fewer BNF models come with Tracer installed currently.

Who Should Use TBS Tracer?

The purpose-built performance makes Tracer a top choice for:

  • Hardcore racers – Every facet is optimised for the lowest latency response to give you an edge around the gates.
  • Speed-focused freestyle – Like Mr. Steele or any pilot who values responsive, twitchy control will appreciate Tracer’s lag-free characteristics.
  • Existing Crossfire users – For those already invested in Crossfire gear, switching to Tracer only requires a quick firmware update for a big latency improvement.

Who Should Avoid TBS Tracer?

  • Long-range pilots – While possible with “Ludicrous” mode, Tracer is focused on short course agility over distance. Look to Crossfire or R9 for priority long range.
  • Cinewhoop pilots – Tracer only comes in 900MHz versions currently, meaning big antennas that can get damaged on prop strikes.
  • Multi-pilot groups – As with Crossfire, Tracer’s limited channel count makes coordination necessary to avoid interference with other Tracer users.

So in summary, Tracer was purpose-built 100% for racing. For other styles, more flexible protocols allow better all-around performance.

ExpressLRS

ExpressLRS exploded onto the scene in 2020 as an open-source control protocol focused on delivering max long-range performance combined with insanely low latency. And its exceptional specs have made ExpressLRS a rising star.

ExpressLRS Specs

  • Frequency bands
    • 900MHz
    • 2.4GHz
  • Channel widths
    • 2MHz (LRFH hub)
    • 5MHz (LRFH)
    • 10MHz (LR12)
  • Modulations
    • LoRa
    • FSK
  • Update rates
    • 150Hz
    • 250Hz
    • 500Hz (“LRFH4”)
  • Output power
    • 10mW
    • 25mW
    • 100mW
    • 500mW
    • 1W
  • Latency
    • 7ms (150Hz)
    • 4ms (250Hz)
  • Range
    • 10km+ (even on 10mW)

ExpressLRS Pros

  • Insane range – Thanks to excellent RF link budget optimization, even 10mW ExpressLRS systems reach multiple kilometers – rivaling some protocols’ maximum range.
  • Extremely low latency – Cutting-edge 500Hz systems hit sub-4ms latency – the best of any protocol today.
  • Next-gen tech – ExpressLRS is pushing the limits of what’s possible with FPV control links, implementing advanced technologies like RPM sensing.
  • Open source ecosystem – An open platform means rapid innovation from a collaborative community.

ExpressLRS Cons

  • DIY assembly required – Being open source, it takes some tinkering to assemble an ExpressLRS module and receiver yourself. Pre-builts are coming to market though.
  • Leading-edge risks – The bleeding-edge tech and rapid pace of development also brings some stability challenges.
  • RF power limitations – Maximum 1W output means extreme, 50km+ long-range flights may still benefit from something like Crossfire’s higher power radios.

Who Should Use ExpressLRS?

The unmatched blend of long-range and low-latency performance makes ExpressLRS a top choice for:

  • Racing pilots – Latency on par with Tracer makes ExpressLRS incredibly responsive around courses. And no channel conflicts due to the spread spectrum modulation.
  • Long-range pilots – Even a small ExpressLRS setup with 25mW output will get you 5-10km, pushing most pilots to the limits of their video system.
  • Tech enthusiasts – The open-source community and rapid innovation of ExpressLRS is exciting for those who always want the latest and greatest.

Who Should Avoid ExpressLRS?

  • Total beginners – The DIY assembly and flashing process requires some existing radio knowledge and tinkering skills.
  • Plug-and-play pilots – You’ll be hard-pressed to find BNF quads with ExpressLRS installed. Most will need a module and receiver installed.
  • Budget buyers – Pre-builts are coming but overall ExpressLRS still costs more than protocols like FRSKY ACCST.

So in summary, ExpressLRS brings an unbeatable blend of bleeding-edge performance and open-source innovation – if you’re willing to pay the premium and “bleeding-edge” tradeoffs that come with it.

How to Choose the Best FPV Control Protocol?

So which protocol is right for you? Here are some key factors to consider:

Your Experience Level

For total beginners, FrSky ACCST is hard to beat. Its ubiquity, cheap cost, easy setup, and “good enough” performance make ACCST a great place to start out. No need to dive into more advanced systems until your skills progress.

Veteran pilots seeking cutting-edge performance will naturally gravitate toward ExpressLRS or TBS Tracer. Their bleeding-edge technology delivers the height of speed and range capabilities.

Your Flying Style

Racers will want the lowest possible latency above all. For pure speed, Tracer and ExpressLRS are tops.

Freestylers and long-rangers will favor range and resilience over shaving milliseconds. Crossfire and Ghost provide a great blend of distance and low-enough latency for aggressive flying.

Cinematic pilots want tiny receivers and durable antenna mounts. Ghost and ExpressLRS shine there.

Locations You’ll Fly

For wide open long-range flights, Crossfire’s high power and huge bandwidth leave room for even 100km+ flights.

In tight bando courses, ExpressLRS’s spectrum hopping and high throughput prevent dropouts even at low power.

Multi-pilot events require coordination to avoid interference on Crossfire’s or Tracer’s limited channels. More pilots can share the air on ACCST or Ghost in 2.4GHz.

Budget Considerations

At the low end, ACCST provides amazing value.reaction, scale, competitive racers will want the prestige of running expensive Tracer or Crossfire gear.

ExpressLRS delivers high-end performance with a more palatable DIY price tag by tapping into the open-source community.

Ease of Use

Out of the box, ACCST and FrSky ACCESS are the most plug-and-play since they’re built into turnkey radio systems.

For smoothest configuration and firmware updating, Crossfire leads the way.

OpenTx wizards may enjoy tweaking ExpressLRS’s cutting-edge open-source environment. Beginners should seek simpler systems.

Future-proofing

The open-source ExpressLRS project sees constant innovation from its collaborative community, ensuring it will stay on the cutting-edge.

Crossfire, Ghost, and Tracer have great features today but may see less active long-term development.

FAQs About Radio Protocols

Final Thoughts

As you can see, there is no single perfect FPV control protocol. Each has strengths and weaknesses that make them more suitable to certain pilots, flying styles, and budgets.

My recommendation is to start with the more accessible, affordable, and beginner-friendly systems like FrSky ACCST. This allows you to get in the air and progress as a pilot without huge investment.

Then as your skills grow and you push into more hardcore racing, long-range, or multi-pilot activities, you’ll know when it’s time to step up to the next level of control link performance.

The high-end protocols definitely provide meaningful benefits – but also come with diminished convenience, at least for now. The cost-benefit balance depends on your personal experience level and ambitions in the hobby.

No matter which protocol you choose, following best practices (like using antennas properly) makes a huge difference in reliability. And any of these modern systems will provide a fun experience!

I hope this guide has broken down the differences between protocols to help you make the best choice. Let me know if you have any other questions!

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Written By Marshall Abrams

My name is Marshall Abrams, and I am a filmmaker and FPV pilot who's been flying professionally for about four years now. Thanks to FPV, I get to travel to so many amazing places, and it's honestly completely changed how I run my business.

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