The Ultimate Guide to Choosing and Using FPV Antennas for FPV Drone

FPV Antennas

FPV Antennas

FPV antennas are the deciding factor that determine the range and signal strength of your FPV system. With so many different types of antennas on the market, it can be overwhelming to choose the right one for your specific setup. In this tutorial, we’ll cover the basics of antenna structure, the different types of antennas available, and provide you with tips on how to choose the right antenna. Whether you’re a beginner or an experienced FPV pilot, this tutorial will provide you with valuable insights on FPV antennas.

What is FPV Antenna

FPV antenna is responsible for transmitting the video feed from the drone’s camera to the pilot’s goggles or monitor in real-time, allowing the pilot to fly the drone while seeing what the drone sees. The quality, performance and configuration of your FPV antennas play a critical role in determining the range, clarity, and reliability of the video transmission.

FPV Antenna Anatomy

An antenna is simply a piece or pieces of wire that convert electrical signal into electromagnetic waves, and vice versa. Regardless of design or external appearance, every antenna consists of the same basic parts:

  • Element: The conductive material that transfers and receives electromagnetic waves.
  • Ground Plane: The ground plane of the antenna is tied to the electrical ground of the device. It is also made of conductive metal and serves as an electrical reference for the state of the element. A properly tuned ground plane can amplify the radio signal emitted or received by the element of any antenna.
  • Coaxial Cable: A special type of shielded wire that carries signal between the connector and antenna element without emitting radio signals. They are used to extend the length of the antenna and often made of rigid material. Coaxial cables are not necessary if the connector is directly connected to the element.
  • Connector – The connector of the antenna is what physically connects the element and ground plane to the video transmitter and receiver.
  • Connector: The physical connection between the antenna and video transmitter/receiver.
what is fpv antenna - anatomy

FPV antenna elements are often made of fragile copper wires and are commonly housed in plastic protective casing. These cases do not weaken the signal and provide support for the antenna during crashes.

Antenna Directionality

When choosing an antenna, the most basic decision is its directionality, which can be either directional or omni-directional.

Omni-directional antennas radiate radio waves equally in all directions, while directional antennas focus their radio waves to one direction.

One classic analogy is bulb vs torch, where the bulb is Omni-directional and the torch is directional. If both light sources are operating at the same power, torch can reach further because it focus the light in one direction, but in the expense of narrower beam width.

Omnidirectional antennas are great for everyday flying and provide good signal coverage all around the pilot. Directional antennas are often used on diversity receivers, where they can be paired with an omni-directional or multiple directional antennas to cover all necessary angles.

Diversity receiver can receive two signals from two antennas and display the stronger signal.

Antenna Polarization

Antenna polarization is a classification of FPV antennas. There are two types:

  • linearly polarized antennas (LP)
  • circularly polarized antennas (CP)

And within circular polarized antennas you have

  • left hand circular polarized antennas (LHCP)
  • right hand circular polarized antennas (RHCP)

Linear Polarization

Linear polarization is used in many basic antennas, such as the stock dipole antennas that come with your VTX and VRX, or even in your home WiFi.

With linear polarization, the signal oscillates either horizontally or vertically in a single plane as it travels.

p1

Circular Polarization

Skew-Planar Wheel, Cloverleaf, and helical antennas are examples of common circularly polarized antennas.

Circular polarization involves transmitting signals on both horizontal and vertical planes with a 90-degree phase shift that looks like a spinning corkscrew.

p51

However, circular polarization has an important consideration: the direction of the radio waves is “spun.” There are only two directions: right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP). If you transmit a radio wave with one antenna, you need to receive that wave with another antenna with the same spin. Therefore, you should use RHCP antennas on your receiver only if your transmitter also has an RHCP antenna, and the same is true for LHCP. Failing to do so will result in a significant loss of signal.

Which Antenna Polarization is Best for FPV Drone?

Circular polarized antennas are generally considered to be better suited for FPV drones for the following reasons:

  1. Linear polarized antennas are much more susceptible to multipath interference compared to CP antennas.
  2. LP antenna range is greatly affected by antenna alignment, and it is almost impossible to maintain good antenna alignment on a quadcopter all the time as it is constantly rotating around all axes.

Linear polarized antennas are widely used due to their structural simplicity. They tend to be smaller, lighter, cheaper, and easier to make. In general, linear polarization is a good choice for long-range as all the energy is focused on a single plane. However, the range advantage is seldom realized due to multipath interference.

To achieve the best reception, both transmitting and receiving ends should use linear polarized antennas, and they have to be aligned to ensure maximum radiation overlap. FPV drones are constantly rotating around all 3 axes, making it almost impossible to maintain perfect alignment. For example, when the transmitter and receiver antennas are at 90 degrees to each other, they will have the least amount of signal overlap, resulting in over 20dB loss in signal strength (over 90% reduction in range), referred to as cross-polarization. LP antennas may be more suited for RC planes, cars, boats, etc.

On the other hand, circular polarized signals always overlap no matter what orientation or angle your FPV drone is at relative to your receiving antenna (no signal loss regardless of the antenna’s alignment). For this reason, circular polarized antennas are the standard for FPV drones.

Another advantage of circular polarized antennas is their ability to reject multipath interference. Multipath interference is a form of noise in your analog video feed that often appears as random color changes, static, scrambled image, and drop-outs. It happens when the signal bounces off objects (such as walls and ground), gets distorted with phase delay, and interferes with the main signal.

For general FPV drone flying, it is recommended to use CP antennas. However, some pilots might prefer specially made LP antennas because they can be made smaller, lighter, and more durable, despite their worse RF performance.

When to use CP antennas

  • When flying close to large objects such as trees, buildings, or in enclosed environments such as car parks and stadiums where there will be a considerable amount of multipathing interference.
  • During acrobatic flying where the aircraft’s orientation and angle are constantly changing.
  • During low altitude flying (proximity flying).

When to use LP antennas

  • During steady straight-line flying without much roll and pitch movement.
  • When antenna size, weight, and durability are the most important considerations.

Can you use LP and CP antennas together?

You can mix linearly polarized antennas and circularly polarized antennas in your FPV system, at the cost of some signal loss. It’s not unheard of for some racers to use a dipole antenna on the drone for weight saving and durability while using a circular antenna on the video receiver. You will suffer from a signal loss of about 3dB (30%), but it’s not that bad for short-range flying such as racing. RHCP/LHCP doesn’t matter in this case. But it’s still better than the worst situation when using only linearly polarized antennas on both ends, where the maximum reduction in signal is 97% (30dB). It’s a compromise between performance and durability.

For ordinary FPV pilots, I still recommend using only CP antennas.

Differences between LHCP and RHCP

Circular polarized antennas are either left-hand (LHCP) or right-hand (RHCP). Transmitter and receiver should have matching antennas otherwise it could result in significant signal loss. If you mix LHCP and RHCP antennas, they will still work but your range is greatly reduced.

This is because LHCP antenna rejects signal from RHCP antenna and vice versa. How much it rejects depends on the Axial Ratio of the antennas.

CP antennas can benefit from this property against multipathing. Every time a CP signal bounces off object it changes its polarization direction. And LHCP antenna rejects RHCP signal and vice versa (cross polarization). Also when one pilot is using LHCP antennas and the other using RHCP, there will be less interference between them.

Therefore you are supposed to use the same type of antenna on both receiver and transmitter. If you mix LHCP and RHCP you will suffer from significant signal loss.

fpv antenna LHCP RHCP - left hand right hand circular polarized

For pilots flying in a group, it’s best to have both LHCP and RHCP antennas for flexibility. If you are just flying alone most of the time, then this doesn’t really matter, both LHCP and RHCP have the same performance. RHCP antennas are more common for analog FPV system, while LHCP is more common for digital FPV systems such as DJI and Avatar.

Antenna Performance

When it comes to FPV antenna design, there are several performance measurements to consider, including:

  • Gain
  • Radiation Pattern
  • Axial ratio
  • VSWR
  • Frequency tuning and range
  • Impedance

Personally, I focus on the first four factors when selecting antennas. However, if you’re buying from a reputable brand, you shouldn’t have to worry too much about these details. After all, we’re not building rockets for NASA here, so there’s no need to give yourself a headache!

If you’re interested in learning more about these concepts, there are plenty of great resources available, such as antenna-theory.com and Wikipedia’s antenna page . In the following sections, I’ll provide a brief explanation of what each term means.

Antenna Gain

Antenna gain is an indicator of a directional antenna’s range and angle of coverage. It is a measure of how much more power an antenna can radiate in a particular direction compared to an isotropic radiator (a theoretical antenna that radiates equally in all directions). Antenna gain is expressed in decibels, or dB.

Higher gain generally means a further range but a narrower beam width. Antenna gain can alter the radiation pattern, which can be seen in the antenna’s datasheet. For VTX antennas, you want to use lower gain, omni-directional antennas so that you get better coverage in all directions around the drone. For VRX antennas, you want to use a combination of low gain omni-directional antenna and mid/high gain directional antenna to get the best of both worlds. If you don’t fly long range, it’s also okay to just use low gain omni-directional antennas on your video receiver.

When dealing with decibels, it is helpful to remember that every 3dB gain you get from your antenna is equivalent to doubling the power of your transmitter. For example, if you can achieve a 6dB gain by swapping to a new antenna with a 200mW video transmitter, it is equivalent to moving to an 800mW video transmitter, and that can give you double the range! (6dB = 3dB + 3dB = two doublings = 4x, 200mW x 4 = 800mW). 

Radiation Pattern

The radiation pattern emitted by your antenna is represented by two charts: one looking down on the antenna, and the other looking from the side. These charts can tell you where the weak spots are.

Here is an example of an antenna with 0 dB gain. As you can see, it’s truly omni-directional and has a nearly perfect spherical radiation pattern.

However, omni-directional antennas in real life usually have weak spots at the top and bottom, and the 3D radiation pattern would look more like a doughnut shape. In a two-dimensional view, it forms a figure-eight pattern in the vertical plane, and a circle in the horizontal plane.

This demonstrates an important point when flying your drone at high altitudes – don’t fly over yourself! The top of the radiation pattern is the area where the gain is weakest, and you have a high likelihood of losing signal.

Here are the radiation charts for an 8dB gain patch antenna. Notice the narrow beam width in both vertical and horizontal planes.

Low dB gain might seem less appealing in terms of range, but it can offer more reliable performance thanks to the more spherical radiation pattern. You can get reasonably strong signals even by pointing the antenna straight at the receiver.

Axial Ratio

In reality, there is no perfect circular polarized antenna. For example, an RHCP antenna might output 90% of RHCP signal with 10% LHCP signal. So there might still be interference even if you were doing everything perfectly. And axial ratio is used to measure this antenna property.

In FPV terms, this is the measurement of how susceptible the antenna is to multipath interference. Antennas with better capabilities of rejecting multipath interference make it easier to fly in areas with lots of concrete and metal.

A perfect circularly polarized antenna would have an axial ratio of 1, while antennas with axial ratios closer to 1 have a greater ability to reject multipath interference.

Frequency and Bandwidth

Antennas are tuned for a specific frequency, for example, the length of a dipole antenna determines the frequency it’s tuned to. The antenna would have the best performance when transmitting and receiving at this frequency.

If you transmit or receive at a slightly higher or lower frequency, the antenna would still have acceptable performance, and this “acceptable range” is the bandwidth. Outside of the bandwidth, signal strength is greatly reduced or even rejected.

You should understand what frequency your antenna is tuned for, and what the bandwidth is, in order to select the most effective channel/frequency to use. Otherwise you will be more likely to get interference and lose picture.

It can even cause overheat and damage to the video transmitter, because sending power into an unmatched antenna can reflect power back where it can build up as heat.

Anyway, for FPV most antennas designed for 5.8GHz should be fine for all the channels in A, B, E, F and R bands, unless it’s stated otherwise in the product specifications.

VSWR

VSWR stands for “Voltage Standing Wave Ratio.” It measures how efficient an antenna is by showing how much energy is bounced back after you put energy into it.

When designing an antenna, we aim for a VSWR value as close to 1 as possible. A VSWR of 1 means we can transfer 100% of the energy into the antenna and out to the real world.

A VSWR between 1 and 2 is considered reasonable, but anything above 2 is poorly performing.

Note that VSWR changes with frequency. When talking about the tuning of an antenna, the frequency with the lowest VSWR is what we mean.

OwlRC makes an affordable  VSWR (or SWR) meter for hobbyist use.

Types of Antennas

We have covered almost all the basics of FPV antenna, now let me introduce the different types of antennas that are commonly used in FPV.

  Omni-directional Directional
Linear Polarization Monopole, Dipole Patch
Circular Polarization Cloverleaf, Skew-Planar Wheel, Pagoda Helical, Patch, Crosshair

Monopole Antenna

Summary:

  • Type: Omni-directional Linear
  • Applications: Radio control transmitters and receivers

A monopole antenna is the simplest form of antenna, consisting of an unshielded solid wire that acts as the antenna element. It is very common in radio receivers due to its low cost and ease of repair. However, it is not as effective as dipole antennas. The length of the exposed wire is crucial as it determines the resonant frequency at which it can pick up signals.”

Dipole Antenna

Summary:

  • Type: Omni-directional Linear
  • Applications: Radio control transmitters and receivers, video transmitters

Many radio and video equipment come with a dipole antenna. They are lightweight and can be made very durable against crashes.

A dipole antenna has a simple design, consisting of two equal-length elements that are perpendicular to each other, typically in a straight line. One element is the radiating element, while the other serves as a ground plane. The dipole antenna has slightly higher gain than a monopole antenna at the expense of reduced effectiveness of the antenna’s vertical performance.

Cloverleaf Antennas

Summary:

  • Type: Omni-directional Circular
  • Applications: Video transmitter and receiver antennas

The cloverleaf and skew-planar wheel have been the most common antennas for mini quad FPV. Cloverleaf has 3 lobes while skew-planar wheel has 4 lobes.

These antennas are omni-directional like dipole. Circularly polarized antennas provide fantastic performance regardless of their orientation relative to one another. They are also less susceptible to multi-pathing, so you can fly around walls and trees with better video quality.

They are however relatively fragile therefore often come in different cases and protection. They are sometimes called “mushroom antenna” because of the shape of the protective housing.

Pagoda Antenna

best fpv antenna - pagoda

Summary:

  • Type: Omni-directional Circular
  • Applications: Video transmitter and receiver antennas

Pagoda is a relatively new antenna design in the FPV scene, released in 2016. It’s an omni-directional circular polarized antenna often used on VTX. The unique design and use of materials (PCB) make it very durable. It’s relatively easy to make and so is very popular among DIY’ers as well.

Cheaper to manufacturer as you can print them on circuit boards and their quality would be roughly the same. However less efficient because of the material used has the wrong impedence (e.g. using fibre glass as dielectric), so you might get lower RSSI than antennas of identical specs that uses wires (using air as dieletric).

It’s cheaper to manufacture as you can print them on circuit boards, and their quality would be roughly the same. However, they are less efficient because they use fiberglass instead of air as a dielectric, so you might get lower RSSI than antennas of identical specs that use wires.

Helical Antenna

Summary:

  • Type: Directional Circular
  • Applications: Video receivers

Helical antennas are spring-shaped, directional circular polarized antennas. The number of turns of coil determines the gain of the antenna. Helical antennas with just 1 or 2 turns have performance comparable to a typical patch antenna. However, adding 6+ turns can make improve the range of the antenna by orders of magnitude.

Patch antenna

Summary:

  • Type: Directional Linear or Circular
  • Applications: Radio control transmitters and video receivers

Patch antennas are also directional and can be found in both linear and circular polarization.

They are relatively inexpensive to manufacture as they can be printed on circuit boards, but their efficiency is inherently lower than that of other types of antennas that use air as dielectric, such as the helical antenna.

Patch antennas generally have less directionality than helical antennas and have a smaller footprint.

Crosshair antenna

Summary:

  • Type: Directional Circular
  • Applications: Video receivers

The crosshair antenna has an active element at a certain distance away from a massive backplate. However, the elements and backplate are separated by an air gap dielectric instead of fibre glass like patch antennas, offering better efficiency.

Considerations in Choosing Antenna for FPV

For beginners, it’s best to start with omni-directional circularly polarized antennas, for example the cloverleaf or pagoda.

Antenna performance relies heavily on decent material and precision, good antennas would therefore cost more. However some top notch antennas can cost 2 to 3 times more than the cheaper ones, while they might only bring 5% or 10% range improvement.

Axial ratio is also an important factor to consider, which isn’t normally mentioned by manufacturer. But you might be able to find out their performance from reviews online.

Ultimately, the best antenna for you will depend on your budget and research on products.

Once you’ve invested in a diversity receiver setup, you can then look into getting some directional antennas to improve signal quality and range.

Receiver Antennas vs Transmitter Antennas

Antennas are made for receiving, transmitting, or both. It’s important to choose the right antenna for each job.

For reliable performance, you should use an omnidirectional antenna on your video transmitter. This is because the quadcopter is always moving and rotating, and it would be impossible to keep a directional antenna aimed at the pilot’s video receiver.

You can use a highly directional antenna on your video receiver since you can point your antenna at certain direction. When you have a diversity receiver on your goggles, you can combine both directional and omni-directional antennas to get the best of both worlds.

 

Notice in this photo the CP antenna on my goggles are RHCP, the one on my quad is LHCP 🙂 They would still work together since they have an axial ratio greater than 1, just not as well as they are supposed to. I didn’t bring the correct antennas with me, and I flew alone that day in close range so it wasn’t a big deal 🙂 But you should avoid doing this.

Antenna Connector Types

For antenna connectors, we normally have SMA and RP-SMA. They are different in design and not compatible with each other, so make sure you buy the right one. Check this article to see the differences between SMA and RP-SMA. If you new to the hobby, try to stick with just SMA for your gear to avoid confusing yourself in the future. There is no difference in performance.

For SMA connector, there are two variants: SMA and RP-SMA. They might look similar but they are not compatible with each other. There’s no difference in performance between the two.

“U.FL” connectors are becoming popular in recently years due to its lightweight and compact size. However, they are extremely fragile and have limited mating cycles.

MMCX is a new type of connector that is being used in VTX and antennas. It’s a perfect balance between SMA and U.FL connectors in terms of weight and size. It’s much stronger than U.FL and have a lot more mating cycle. This is the my personal favorite at the moment.

MMCX is the balance between SMA and U.FL in terms of weight, size and robustness. It has more mating cycles and can survive harder crashes than UFL and yet it has a smaller footprint than SMA.

Durability

When choosing FPV antenna for FPV drones it’s important to consider its durability. The antenna is mounted externally, it is prone to damage and will likely experience many crashes during its lifetime. Therefore, it’s important to choose an antenna that can withstand the inevitable abuse it will take, especially if you crash often. Consider how robust and durable the antenna is when making your decision, pick one that comes with strong protective housing.

Weight

One thing people usually overlook is the size and weight of the antenna. It’s becoming more important as mini quads are getting lighter and lighter. Every gram you save can improve the performance of your quad.

The size and weight of an antenna are often overlooked, but they are becoming increasingly important as FPV drones are becoming lighter. Saving even a few grams can improve your quad’s performance and flight time. Therefore, it’s important to take the weight of the antenna into consideration when selecting one for your mini quad.

How to Mount VTX Antenna?

When mounting your VTX (video transmitter) antenna, the most important thing is to keep it away from any conductive materials. This is because those materials can block or absorb radio waves, which will weaken your signal.

It’s also important to use a rigid antenna, since a longer antenna can create vibrations during flight that make it harder to tune your drone or cause more noise.

Geprc Smart 35 Tbs Crossfire Nano Antenna T Immortal

 

The best orientation for your VTX antenna depends on your flying style. If you spend most of your time cruising, your quadcopter may be tilted forward 20 to 30 degrees. By mounting your antenna tilted back, it makes sure it’s pointing vertically during flight which is the optimal antenna position.

Stp Hobby Armor 5 Fpv Drone Rushfpv Rx Vtx Antenna Gps Mount

 

For racing drones, VTX antennas are often mounted inside a 3D printed TPU mount for protection. However, this may not be the best choice for long-range flying.

Iflight Mach R5 Hd Bnf Racing Drone Vtx Rx Antenna Xt60

 

How to Mount Video Receiver Antenna?

Mounting the video receiver antenna requires consideration of the type of setup you have. For a single antenna receiver, a circular polarized omni-directional antenna is recommended, while a directional and an omni-directional antenna are suggested for diversity setups for overall better performance.

 

For long-range flying, it’s a common practice to have your video receiver module on a ground station to prevent unexpected changes in antenna orientation due to body movements. A spotter can also help adjust the patch antenna to ensure it’s pointing in the right direction. If you have the patch antenna on your goggles, you can try moving your head to point it at your model when the signal gets weak.

Using SMA Adapters

You can use adapters to convert between different connectors (RP-SMA, SMA, MMCX, U.FL, etc.). These adapters even come with 45-degree or 90-degree angles if you want to point the antenna at a certain angle.

However, there is some signal loss when using these adapters or extension coax cables, usually a few percent of power loss depending on the quality and design.

But sometimes the benefits of using an adapter or extension outweigh the little signal loss. For example, you can use an extension coax wire to increase the separation between the VTX antenna and radio receiver or other sources of interference. Or you can use a 45-degree adapter to optimize your video receiver antenna orientation.

DIY FPV Antenna

Making your own FPV antenna may seem daunting, but it can be a cost-effective option. You don’t need to fully understand antenna design to make a good one – the materials are cheap and readily available. All you need is some coaxial cable, copper wire, and plastic supports, and to follow a simple recipe while being precise in your measurements.

However, keep in mind that making a high-performing antenna requires a lot of precision, and even small errors can significantly impact its effectiveness. If you’re looking for top-notch performance, it’s best to buy antennas from reputable vendors.

Conclusion

So that covers some of basics and considerations in choosing your 5.8GHz FPV antenna, and some antenna recommendations for FPV flying. I hope this guide has helped you to choose the best FPV antenna for your mini quad!

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