Video transmitter, or VTX, is a crucial part in FPV drones. It is what separates the FPV from non-FPV drones. Here’s a quick guide on all you need to know about VTX, and how to choose a VTX for your FPV drone.
Get an FPV VTX with the most legal channels and adjustable output power. You need high power for long range, while racing requires low power. The VTX should support telemetry so that you can adjust settings remotely. Pit mode is very useful if you are racing. Majority of the VTX are analog, but you should consider getting digital VTX.
Continue reading to understand better about VTX and the the specs that you should pay attention to.
What is An FPV Video Transmitter
An FPV VTX is essentially a component that transfers the video captured by the drone camera in the form of radio to your FPV goggles. VTX allows you to have the first person view experience. Without a VTX, your drone becomes a “normal” drone.
VTX Frequency and Licensing Requirement
Generally, the VTX transmit video data from the camera to your FPV video feed through the 5.8 GHz ISM band. In the US, the use of VTX is subjected to the Federal Communications Commission (FCC)’s regulation. You will need a ham radio license to operate most VTX. Check out this article for more details on how to get the required license.
To avoid the need of a ham radio license, you can use VTX which is FCC certified. However, do note that you really don’t have many options at least for now, since most VTX are not FCC certified. While they are not FCC certified, it is legal to use them, for as long as you have a ham radio license.
FPV VTX Channels
A VTX can operate one or more bands, or frequencies. Commonly used bands include “A,” “B,” “E,” “F (FatShark),” and “R (Raceband)”. Each of those bands has 8 distinct frequencies, also known as channels.
Essentially, you can operate your FPV VTX at different channels or frequencies within the 5.8 GHz ISM band. But how does each channel make a difference?
Well, the main reason for using different channels is to avoid signal interference with other pilots. As a rule of thumb, when flying in a group, no one should use the same VTX channel, and no one should use channels that can cause intermodulation distortion when interacting with other channels (check out this article on how to avoid interference when flying in a group).
Hence, when you choose a VTX, it is important to consider the available bands and channels your VTX can operate. The more bands or channels your VTX can operate, the more versatile you are when grouping with other pilots.
Most of the affordable VTX nowadays can operate at up to 37 or 40 channels. So, make sure your VTX can do that as well. Do take note that some products have channels outside the allowable frequency. Make sure you don’t use them!
VTX Power Output
The power rating of a VTX can range from 25 mW to 600 mW, or even more than 1000 mW.
At a higher power, your VTX will have a better signal and further range. In contrast, you will have a weaker signal and shorter range with a 25 mW VTX. However, the relation between range or signal strength (which translate to video quality) and power is not linear.
A 50 mW VTX is not twice as good as a 25 mW VTX. This is because a lot of the power is converted to heat due to efficiency issues. As a result, high power VTX turns hot faster even with a greater heat sink.
On top of that, high power VTX also have their own issues when operating in crowded space. At crowded areas, the signal from the VTX may go directly to the receiver from one direction, at the same time bouncing off certain surfaces such as walls before reaching the receiver from another direction. This is called multipathing and it causes interference.
Another issue with high power VTX is the interference with other pilots’ video systems. When you use high power VTX, you may bleed into other people’s video feed. That’s why pilots use only 25 mW VTX when flying in groups.
For the purpose of FPV racing, you should choose a VTX with 25 mW output, or switchable power from 25-600 mW. 25 mW power output is good enough for flying FPV races while 600 mW is more suitable for solo or long range. Having a VTX with switchable power gives you flexibility to fly in group and solo.
Pit mode is essentially a mode where your VTX is operating at the lowest possible power, at 0.1 mW or even lower. You would want your VTX to enter pit mode during start up, after crash or as you change the channel.
Pit mode is crucial when you are flying in groups. As you turn on your VTX or switch channels, the channel of your VTX might interfere with the channels used by other pilots inflight. Pit mode allows you to change your VTX channel or power on your drone without affecting those who are flying nearby.
But why do you need pit mode when your drone crashes? Well, VTX heats up quickly, especially if there is no air flow to cool it down after your drone crashes. It might take some time before you can go to retrieve your drone if there are other pilots flying. Going into the pit mode reduces the power output and prevents your VTX from overheating while the race goes on.
Nowadays, all VTX should come with VTX control or VTX telemetry which makes your life easier. It basically allows you to change the setting of your VTX through the On Screen Display (OSD) menu. Smart Audio and Tramp Telemetry are the 2 popular VTX control used in the market.
The settings that you can change through the OSD include the power output and channel, which you will need to change quite often if you frequently fly in groups.
Without the VTX control, you can only change your setting by pressing a button or DIP switches on the hardware itself, which is enclosed within your drone frame. This is really troublesome because the switches are hard to reach.
Besides, if your VTX supports 40 channels, you need to memorize the DIP switches pattern for all those channels; or you may need to press the button for 30 times if you need to change from 1st channel to 31st channel (since each press brings you to the next channel).
There is another drawback of push buttons. You can’t change channels without turning on your VTX. As you push the button, you broadcast channels that might interfere with someone who is flying. Because of that, with the push button you should only change channels when no one is flying, or after entering pit mode.
Hence, You should definitely consider VTX with Smart Audio or Tramp Telemetry, or any VTX that has a smarter way to change channels and power.
Digital vs Analog VTX
When you do your shopping, you might notice that some of the VTX are labeled as “digital” while some are not. Instead, their specifications mention NTSC and/or PAL video systems. So what exactly does that mean?
In the world of video, there are 2 main “systems” – digital and analog. Both differ in the way the signals are transmitted. I won’t go into details of the mechanism. What you need to remember is, NTSC and PAL are analog systems. When you choose your VTX, you need to make sure it is compatible with your camera and FPV goggle in terms of whether it is digital or analog.
Here’s a table of comparison between analog and digital video systems. You can find out more details on analog versus digital FPV here.
|Output at low signal||Reduced resolution, flicker image||Static and flicker image|
In drone racing, many people are still using analog video systems because it is way cheaper and lightweight. If you are flying smaller drones like 3” or 2.5”, the extra weight can significantly impact your drone’s performance.
There are 3 digital FPV systems available: the DJI system, Fat Shark or Walksnail Avatar system, and the HDZero System. None of them are compatible with each other (except for Fat Shark and Walksnail systems, which are basically identical).
On top of that, digital systems require you to use specific components, from camera to goggle. There isn’t much flexibility and options.
Having said that, the digital system is definitely improving and slowly gaining more users. The analog may become history in the near future. Who knows.
Like all electronic components, the VTX has a voltage input rating so that you can supply it with the right voltage. The typical voltage rating of a VTX is around 2-5 V. You need to make sure the power supply is consistent within the advised input to avoid frying your VTX.
The VTX needs to be connected to an antenna for signal transmission. Pay attention to the antenna connector when buying your VTX (and antenna).
Common connectors used on a VTX are SMA, RP-SMA, IPEX/U.FL, and MMCX. Each of them has a different design. Make sure your VTX and antenna are compatible in terms of the connector type.
Both SMA and RP-SMA are strong and sturdy. They can withstand more crashes. However, they are heavier, which may not be suitable for smaller quads or whoops.
Smaller drones usually use FPV antennas use U.FL connector since it is small and lightweight. However, it is more fragile.
U.FL connectors support approximately 30 mating cycles. That means you can only unplug and re-plug the antenna for not more than 30 times before damaging the connectors. To some people, this is a set back. But, HEY! Who is going to unplug/re-plug the FPV antennas for so many times?!
MMCX is something in between SMA/RP-SMA and U.FL. That means it is stronger than the U.FL, and lightweight compared to SMA/RP-SMA connector.
In the case where you have a VTX and antenna with different connectors, you can use an adapter to connect them. However, I’d advise you to get a pair of compatible VTX/antenna because the adapter will result in some degree of signal loss.
Depending on the specs, VTX can be big or small in size. In general, a bigger VTX has higher power output (and bigger heatsink to dissipate the heat generated) and more features such as VTX control. You just have to make sure that your VTX fits onto your drone frame.
Video transmitter prices can range from $5-$100. Those at the higher pricing end are generally of better quality.
Generally, you would want to spend $30-40 on an analog VTX if you use your drone for racing. You should definitely opt for a high end digital video system if HD video feed is your priority.
There are a lot more features that an FPV video transmitter could have. Some of the notable features include:
Able to power up other components
Sometimes, you will see a voltage and current “output” on VTX specs. This is not a typo or misprint. Those VTX can power up your drone components such as your camera and flight controller (FC).
Having a VTX with power output can be handy because it makes wiring simpler. You would want to make sure the voltage provided is enough to power up your camera/FC, and the current draw of your camera/FC is lower than the current output so that you don’t overheat your VTX.
Some VTX comes with a built-in microphone. It allows you to hear the sound of your motors and the winds as you fly. Just imagine playing a video game with and without sound effect. While the sound of motors is noisy for some people, the rest prefer to have some background noise for a more immersive experience.
2022 Best VTX for FPV Drones
The market is flooded with lots of VTX and here are my top picks. Note that I’ve included affiliate links below. If you make any purchases through my links, I will get a small commissions for qualified purchases. This help me to maintain the site without additional cost to you.
Best Analog VTX
Top of the Line – TBS Unify Pro32 5G8 HV
The TBS Unify Pro32 5G8 HV series is one of the best and most popular VTX series for racing, freestyle, and long range.
The nano version weighs only 1 g, and has an U.FL antenna connector commonly used in racing drone. It has a maximum output power of 500 mW. The full size version can go up to 1 W output.
TBS Unify Pro32 is packed with crucial functionality such as Smart Audio (also known as VTX telemetry), pit mode, and so on. If you are using TBS radios, you should consider TBS Unify to enjoy the features of TBS ecosystem such as MyVTX, to further improve your user experience.
Best Racing – ImmersionRC Tramp Nano
ImmersionRC Tramp Nano is the best VTX for FPV racing. Weighing only 1 g, it has whatever you could expect from a good VTX. It truly shines when used in conjunction with the Touch ‘n’ Race or TNR Wand, where you can easily adjust the power output and channel wirelessly.
If you are planning to use IRC Ghost radio (which is a good idea), you can get the IRC Tramp/Ghost Hybrid which includes both Ghost radio receiver and Tramp VTX on the same board. This reduces the complexity of building your drone.
Best Budget – HGLRC Zeus Nano
The HGLRC Zeus Nano is a budget VTX that comes with 3 mounting sizes on a single chip. It has all the basic features that you need from a good VTX: adjustable output power up to 350 mW, Pit mode, supports 40 channels, and VTX control. It even comes with a microphone.
If you plan to build multiple drones, the HGLRC Zeus Nano can prevent you from burning a hole in your pocket.
Best Digital FPV VTX
For digital FPV, you need to first decide which system to use. DJI has the most robust system, but its so expensive. Meanwhile, the Fat Shark/Walksnail Avatar is lack flexibility. I prefer HDZero because there are options for racing, freestyle and mini quadcopter.
Top of the Line – O3 Air Unit
When we talk about digital FPV, DJI is always the first thing that comes into our mind. The O3 Air Unit is arguably the best in class digital VTX (and camera) that leads the digital FPV market.
The O3 Air Unit features low latency, superior range up to 10 km, and HD video. It can even link up with a DJI radio transmitter, eliminating the need for an additional radio receiver on your drone.
The O3 Air Unit comes with an action camera that serves as the FPV camera. It can do 4K stabilized onboard recording at 60 fps. That means you do not need another action camera to record HD videos.
The camera is expensive, so you want to make sure you don’t crash a lot.
Note that the lens of O3 Air Unit camera is bigger than any other FPV camera. It may not fit perfectly in some quadcopter frames.
Although the O3 Air Unit is compatible with the DJI FPV Goggles v2, it works best with DJI Goggles 2 (they are not the same!). The DJI Goggles 2 can support higher resolution and frame rate of the O3.
You can also buy the older Air Units such as those listed in the below table. They have a shorter range of 4 km, and do not have an action camera as the drone camera. Except for the full size Air Unit, the rest are smaller than O3.
Caddx Air Unit Micro
Caddx Polar Micro Air Unit
Caddx Polar Micro Vista
Nebula Pro Vista
Nebula Pro Nano
RunCam Link Phoenix HD
RunCam Link Phoenix HD Nano
Air Unit Size
You would have noticed the key differences between them are the size of the Air Unit and/or camera, the overall weight, DVR, and the overall resolution/frame per second (FPS). Choose one that fits your needs. Note that the higher the FPS, the lower the latency.
Best Digital FPV VTX for Racing – HDZero Race V2
After years of domination by DJI in digital FPV, we finally have a contender: HDZero by Divimath.
Divimath has taken the feedback on digital FPV (which was predominantly made on DJI’s products), and came out with their HDZero series.
The HDZero Race V2 is lightweight, and not bulky unlike the DJI Air Unit. Thanks to its super low latency, you can install HDZero into your racing drone. In fact, Evan Turner won MultiGP in 2021 using a drone with HDZero build.
In a nutshell, HDZero Race V2 is the best VTX for racing pilots who wants to move to digital FPV.
The HDZero Race V2 comes only with Raceband. Its output power is 25-200 mW, which is more than enough for racing.
There is a smaller variant for whoops, which doesn’t come with Smart Audio, and can support 40 channels.
To use HDZero VTX, make sure you have a HDZero VRX (GetFPV | Banggood). The VRX can be mounted on most FPV goggles. Alternatively, get the HDZero goggles.
Best Versatile Digital FPV VTX – HDZero Freestyle
The HDZero Freestyle VTX is the latest addition to the digital FPV family. It has up to 1 W power output, and it is a great alternative to DJI for those who prefer not to use DJI due to whatever reasons.
This unit has a 30×30 mm mounting pattern, but the overall unit is close to 40×40 mm. Hence, it may not fit into all frames.
The HDZero Freestyle requires 2-4S input. Hence, you need a voltage regulator (included) if you are running on 6S. The manufacturer also mandates having a large capacitor connected to your battery lead to smoothen the power supply of your drone.
At the time of writing, HDZero Freestyle comes with a U.FL connector. It is lightweight, but it is relatively fragile compared with other types of connectors.
If you are looking for the best HD digital FPV system, DJI is clearly the winner in terms of range and video quality. But if you are looking for versatility (you can use analog goggles mounted with HDZero VRX), cost factor, and you fly mainly in an open field, HDZero Freestyle is the one to go.
Being a component that defines FPV, getting the right VTX is crucial for any FPV drone pilot. With so many features and specs to look at, I hope this guide gives you clear direction and helps you in selecting the most suitable VTX for your FPV drone.