What Is a FPV Receiver?
First we need to discuss what FPV receivers are and what is their job on a drone. Receivers are like ears on a drone that listen for your radio transmitter commands processes them and sends them further to flight controller that then converts them back into the commands and executes them.
Some fpv receivers have better range and penetration than others but we will get to that in a moment.
Do I Need Receiver On My Drone?
Receiver is crucial component for your drone as without one you have no way of telling your drone what to do, some recent digital systems like DJI Air unit, DJI O3 and Caddx vista(smaller version of DJI original air unit made by Caddx) have built in receivers that can be used only with DJI transmitters, but you can still use regular external receivers.
Receiver Telemetry, What Is It?
Another feature on receivers is telemetry, But what does it do?
In short receiver telemetry is data that is transferred in between TX and RX, for example:
- Battery voltage
- Current draw
- Stick positions
- Flight mode
- RSSI
- Link quality
- Transmitting power
- GPS coordinates
- GPS altitude
- GPS satellites acquired
- Magnetic orientation and much more.
What Are Key Features Of Receivers?
There are various frequencies at which FPV receivers operate like 900mhz or 2.4Ghz while 5.8Ghz is mostly used for video transmission.
Receivers use multiple channels to handle control inputs on which you can assign your desired controls for your drone.
Some of those controls can be mandatory like:
- Arm (arming motors)
- Pre arm (safety feature used so you don’t arm motors by accident, but is optional and everyone should use it if you ask me)
Or some of your own choice, some I personally use on all of my drones:
- Fly mode
- Flip after a crash
- Beeper
- Air mode (I use it on switch instead always on)
You can even do some more advanced stuff like changing Rates on switch or even controlling custom gimbal, possibilities are almost limitless.
Popular FPV Receiver Protocols
Some of the most popular RX protocols are:
- Frsky
- Frsky R9
- Flysky
- Tracer
- Ghost
- Crossfire
- ExpressLRS
While FrSky and FlySky are now pretty outdated they still can be solid budget option for close range flights.
ImmersionRC made one of the best analogue diversity modules for video system, and they also made Ghost protocol and receivers that operate at 2.4Ghz and can switch between lower refresh rate all the way to 15hz for achieving much longer range or increasing refresh rate all the way up to 222hz to get super responsive feedback and is used a lot for FPV drone racing.
Crossfire and Tracer protocols were made by trusty TBS (team blacksheep) and are some of most popular and used receivers to date.
Crossfire operates on 868/915Mhz 50-150hz while tracer operates on 2.4Ghz and is 250hz refresh rate
ExpressLRS operates on 915Mhz or 2.4Ghz depending which one you pick, and goes up to 1000hz, yes you heard me well… ELRS is most recent receiver protocol and it is open source project. ELRS has shocked industry by its performance and if I recall well holds record for most range of all receivers at over 100km, not that that FPV pilot would carry gear necessary for such range, I just thought it is amazing information to know.
Binding Process
Now why would I even bring binding process into this?
Reason why crossfire has so much going for it is not just its amazing performance, it is in binding process and reliability as well!
To bind crossfire all you have to do is put transmitter and receiver into binding modes and once its bound it is bound forever unless you reset it, you plug in your battery and it is connected before you look at your transmitter, its just so simple.
To bind Ghost you need to update external module to latest firmware to be sure it will support receiver firmware it came with, set correct settings on external module to match ones you want to use and press bind. After external module enters bind mode, you have to press button on ghost receiver within 30 seconds of starting bind mode on external module. After this it should bind and if receiver needs update it will prompt you on external modules screen where you can confirm or deny update
Frsky and Flysky HAVE to be on exact same firmware (TX and RX) otherwise it wont bind, and since its so old they will almost never be same firmware when you get them and flashing is gimmicky at best.
ELRS got a lot of hate at beginning as it was super complicated to get it working which included flashing, setting binding phrase and so on, but by now they made it so much better, simpler experience it is for me on par with TBS ones.
Since it is still so fresh most receivers you buy will come with newer firmware which is easy to set up as plugging in your battery with receiver wired on flight controller, waiting a minute for it to open wifi connection, entering “expresslrs” for password and going to 10.0.0.1 in your browser to type your binding phrase and clicking save, that is it and it sounds much longer process than it actually is. After that it will bind every time just like TBS receivers and simply work.
So Which One To Pick?
To decide which one to pick for you, first you need to conclude on transmitter, if you already have transmitter you need to know what protocols it supports, if you don’t have transmitter yet you can decide on few key points.
My personal take is to not bother beyond TBS and ELRS as they are not that expensive compared to frsky and others but are far beyond in performance. The most simple setup goes to TBS ones but ELRS is performing better and is not much more complicated by now, and is open source constantly being updated with a lot of people working in unison to make ELRS even better.
TBS Crossfire has amazing controller style radio TBS Tango 2 which I personally use since I started with FPV, I did mod it with internal 1w ELRS module(would not recommend as it includes destroying housing internally).
TBS Tracer is same as Crossfire setup wise and is not compatible with same radios as they work on different frequencies, one amazing radio for tracer is TBS Mambo radio with built in tracer protocol (Ethix mambo is same radio with slight differences mostly in looks)
ImmersionRC Ghost seems as amazing pick too but I don’t see it be nearly as used as TBS and ELRS and I think its just unfortunate timing of release and placement as its not far from Crossfire and its not as good as ELRS so it ended up being mostly used for racing and lack of availability was not helping. It also required to be used with external module as there is no transmitters with built in Ghost which made it inconvenient for people that are not fans of external modules.
ELRS is still fresh so not many radios come with it but of course there are protocol modules you can insert in a lot of radios to make them compatible.
Some of amazing radios with ELRS built in are Radiomaster Pocket and Radiomaster Boxxer ELRS version(it has non ELRS version so beware!)
One radio worth of mention is Radiomaster tx16s as it is one of most popular ones for a long time due to its awesome build quality and performance.
Conclusion
Based on what transmitter you have by or have chosen to get, you need to decide if you want to use native or you don’t mind adding module to make your radio compatible with receiver protocol lies in personal choice, but external modules cost extra don’t forget that and add to overall weight and size.
Did I mention most new tinywhoop drones come with ELRS build into all in one boards? Yes ELRS has some miniature receivers it is actually hard to believe.
And if you already have Frsky or any taranis transmitter you can either add external module or check which protocol runs in that specific transmitter as ACCST and ACCESS for example wont work one on another it has to be correct one and get receiver with the same protocol.