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FPV for dummies. All you need to know about FPV Racing Drones.

Every day the acronym FPV is becoming more and more popular among the RC hobbyist community and the public in general. We have prepared this article to explain in detail what FPV is, what the elements are necessary to create your own FPV system, how to set them up and finally some tips to improve your FPV experience.

1. What is FPV?

FPV is the action of controlling a UAV (Unmanned Ariel Vehicle) through live stream video relayed by a camera on board to a ground station monitor device. FPV stands for First Person View and is the closest sensation to being a real pilot. Lately Youtube is flooded with thousands of videos of aircrafts flying at high speeds through a forest or an abandoned building, reminding us of the sci-fi movies and video games that we like a lot.

It is not a simple hobby anymore, with the rapidly growing amount of people that are flying FPV this activity has turned into an organized sport with many official leagues created around the world.

FPV suits almost everyone regardless if you like fast racing style or relaxed aerial filming which carries certain benefits like more precise control, more agile flying, going further and higher.

2. Build your own or buy it ready to fly?

The answer for this question depends on your electrical skills and understanding of the theory behind the system. If you don't feel comfortable with your soldering skills or don't have enough time, you can also try a ready to fly option like the Walkera Runner 250 FPV

 3. FPV main components

A basic FPV system consist of:

- The camera
- The transmitter (Tx)
- The Video receiver (Rx)
- A video display device.

The camera must be positioned in the front of the aircraft to achieve that feeling of being on board and depending on how fast you like to fly you will have to adjust the angle of the camera, otherwise it will be pointing to the ground. It is good to start with the camera straight forward, then increase the angle to 10 - 15 degrees for an intermediate speed level and 30 degrees and up for an advanced speed level. The video transmitter sends the wireless signal to a ground station receiver and provides video that you can see in a display device like a monitor or goggles. You can go further and add more sophisticated functions to your FPV system like on Screen Displaying information and adding an OSD device.

FPV CAMERA

Your eyes in the sky, when choosing your camera you should try to focus on certain characteristics like the image resolution, the ability for the camera to adjust to different light conditions and low latency. There is a lot of good options out there but the main kind of cameras used in FPV are the CCD or CMOS.

Image resolution

The image resolution is determined by the TVL (TV lines) measurement unit. The higher the TVL the better. The most common cameras used in FPV are 600TVL or 700TVL which provides a decent image quality but you can take it up a notch and use an 800TVL or even a 1200TVL which seems to work much better with HD monitors or goggles.

Video output. NTSC - PAL

Depending on which part of the world you are located you may have to chose what video output your device runs, however this is not an issue anymore because some FPV dedicated devices can switch between these two modes.

 Sensor type

CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor) image sensors are two different technologies for capturing images digitally. Each has unique strengths and weaknesses giving advantages in different applications. The cameras with CCD sensor is a bit more expensive than CMOS cameras but have better performance in scenarios with different light conditions due to it's advantage of processing the information and obtaining a digital signal.

 

Cameras like Gopro and Mobius use the CMOS sensor. You can use them for FPV but you will notice higher latency beside the slow response to light changes. We strongly recommend to use a dedicated FPV camera like the Eachine FPV Camera which includes the video transmitter, a current filter and it's a plug and play option.

 VIDEO TRANSMITTER AND RECEIVER

These two elements are key to achieve a good quality and reliable video. We don't want to lose the video signal suddenly causing a crash or even worse to lose our beautifully built aircraft.

Frequencies

 The most common frequencies used in FPV are.

- 900 Mhz
-1.2 ghz
- 1.3 ghz
- 2.4 ghz
-5.8 ghz

The lower the frequency, the better penetration ability. Also the lower the frequency the bigger the antenna that must be used. Before using an FPV device you should research about local Region or Country regulations that may apply.

The most popular frequency is 5.8 ghz because it is legal in most countries, cheaper, it uses a small antenna and it doesn't cause interference with the radio control system.

Some receivers have up to 32 channels so you have the option to select different channels when flying with others so your video signals are not conflicting causing interference.

Transmission Power

These radios can be rated at 25mW,  250mW, 600mW and even 1000mW. The higher the power the longer the transmission range. We have tested these radios and for FPV racing purposes we find the 250mW radio has enough power to transmit decent video signal up to 1 Km with a clover leaf antenna in a space without obstacles like buildings or trees.

Types of antennas

For FPV purposes we will talk about the most commonly used antennas and their characteristics.

1. Linear polarized antenna: these are the "normal" antennas which usually come from stock with the radios. These antennas are linear polarized, which means that they radiate in only one aircraft, either vertically or horizontally.

2. Circular polarized antenna: Circular polarized antennas emit a signal similar to a doughnut when you look it in 3D diagrams, these are the most popular antennas due to their ability to maintain a consistent video signal regardless the position of the antenna. There are two kinds of circular polarized antennas, the Clover leaf antennas have 3 lobs and they are ideal for transmitters. Skew planar antennas have 4 leaves and they are ideal for receivers.

Which antenna should I use and why?

The main difference between these first two antennas is the way they signal is spread. Linear polarized antennas transmit waves in a single plane.

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When using a linear polarized antenna, the position of the aircraft in the air is not always straight causing loss in signal strength, an effect called crossed polarization. Here is where the circular polarized antennas become protagonists. 
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Instead of transmitting in just one plane, a circular polarized antenna transmits in both planes at once, with a 90° phase shift between the two planes. The signal in this case would not look like a sine-wave transmitted by the linear polarized antennas but rather like a corkscrew. A circular polarized antenna can "talk" with a linear polarized antenna without losing signal strength significantly. There is only a 3dB loss regardless of the orientation of the two antennas. This could be a good solution for many FPVers but the video signal quality can get even better when using two circular antennas with the same polarization.
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3. Helical and patch antenna: They are directional antennas. They offer better range and penetration but you will get a narrower beam meaning that the antenna has to face the copter or aircraft to get best performance.
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Comparison between an onmi-directional antenna and a directional antenna effective range.
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Helical antenna                                  Patch antenna
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CONNECTORS. SMA - RP-SMA.
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SMA stands for Sub Miniature version A and RP-SMA stands for Reverse Polarity SMA.
The second is a variation of the first and they have reversed the gender of the interface. Here we have a picture of the SMA connectors family. 
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Female RP-SMA connector has a female contact body and a male inner pin contact. A male RP-SMA connector is the opposite in both respects — male body (inside threads) with a female inner sleeve contact. While Female SMA connectors has a female contact body and a female inner hole sleeve contact, and the male SMA is opposite.
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GROUND STATION
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For ground station we have two options: Monitor or goggles. When you are using a monitor you will have the advantage of switch between perspectives, very useful when you are learning to land and take off. The goggles require a lot more of commitment but the immersive experience is rewarding, you will have more precise control and won't have to worry about sunlight. Also goggles are easier to carry and the battery last longer.
This is more a personal preference, some people can experience dizziness or headaches and if you have an eye condition it can affect the usage of goggles.
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What to consider when purchasing goggles?
 
- Frequency. Double check that both your transmitter and receiver are compatible. For example: FatShark goggles works on F band so you will have to find a transmitter that transmit in the same band. Most of the 5.8 Ghz 32 channels transmitters work in this band.  
Resolution: It makes a big difference when you have a clear and detailed image of your flight path, the camera plays a very important role in this aspect.
- DVR. Some goggles have this function, if you are looking to record your flights make sure your choice includes a built in DVR.
-Headtracking. This feature allows to bind the camera on board to pilot's head motion increasing the immersive experience providing more natural moving and expanding the Field of View.
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What to consider when purchasing monitors?
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- Correct video input. make sure the monitor supports AV input, that works with your video receiver.
- No blue screen. Monitors that don't turn blue when the signal is weak are the best choice for FPV. The reason is that even when the signal is weak and you see static on the screen, sometimes you might still be able to make up a vague image from it which lets you to turn back or do your stuff.
- Built in receiver and battery. A screen that includes the receiver and the battery built in makes everything easier and ultra portable.
- Size. A 7 inches monitor is perfect talking about portability. Although a bigger screen can give you better detail.
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OSD
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An on-screen display (abbreviated OSD) is an image superimposed on a screen picture, showing relevant information about your aircraft like the battery voltage, altitude, speed, etc. This is complete optional but is always good to have this information at disposition.
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POWER FILTER
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If you are using the same battery to power the aircraft and the FPV system you likely will have noisy image, that's why is a good practice to include a power filter to provide clean power to the FPV system. Some dedicated FPV systems include a fulter in the main conector, if yours don't, you can use a UBEC having in mind the operational voltage of the camera and transmitter.
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WIRING
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Finally, the following diagram shows how to connect your FPV system using a Naze 32 Pro.
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We hope that you could find this guide useful and help to make your path to become the next racing drone champion easier.

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