FPV antenna is the deciding factor that determines the range and signal strength of your FPV system. This guide will explain the basics of 5.8Ghz antennas used on mini quad VTX and VRX, and hopefully it will help you choose the best FPV antenna.
At the end of this article, we featured 5 of the most popular FPV antennas which were recommended by the multirotor community.
To learn more, make sure to check out our complete guide to FPV system.
Index of Content
- What is FPV Antenna
- Antenna Anatomy
- Antenna Polarization – Linear or Circular
- Directional and Omni-directional Antennas
- Antenna Performance Measurements
- Types of FPV Antenna
- Considerations in Choosing Antenna for FPV
- Best FPV Antennas for Mini Quad
What is FPV Antenna
An antenna converts electrical power into electromagnetic waves and vice versa.
In FPV, antennas (or antennae) enable wireless communication between the video transmitter (VTX) and receiver (VRX). Antennas in your FPV system are critical elements that determine the range and signal quality.
FPV Antenna Anatomy
Every antenna consists of the same basic parts regardless design or external appearance.
- Active Element – conductive material that transfers and receives radio wave signal in the air
- Coaxial Cable – a special shielded cable that carries signal from the connector to the antenna element without emitting radio signals. Coaxial cables are used to extend the height of the antenna, and often are made of rigid material so it can be bent to any desired angle. Coaxial cables are not necessary if the connector is directly connected to the element
- Connector – used to connect the antenna to a video transmitter or receiver.
FPV antenna elements are made of fragile copper wires or other conductive material, therefore it’s common to see antennas come in plastic protective housing. These housing or cases do not weaken the signal and provides support for the antenna in crashes.
Antenna Polarization – Linear or Circular
Antenna polarization is a classification of FPV antennas. There are two types:
- linearly polarized antennas
- circularly polarized antennas
We explained the technical differences between Linear and Circular Polarized antennas previously.
Circular polarized (CP) antennas are the standard aftermarket upgrade for most FPV systems, because: 1. linear polarized (LP) antennas are very sensitive to multipathing interference; 2. LP antennas have to be aligned to work well. Antenna alignment is very hard to maintain on a quadcopter as it’s moving around all the time.
Multi-Pathing in FPV is when the video signal bounces off objects such as trees, walls or ground, the reflected signals become out of phase and could interfere with the main signal. Multipath interference often appears as random static in the video feed.
Therefore, for general mini quad FPV flying it’s best to use circular polarized antennas. However pilots sometime schoose linear polarized antennas because they are smaller, lighter, and more durable, although they do have worse RF performance.
LHCP and RHCP
Between circular polarized antennas, they can be either “left-hand” (LHCP) or “right-hand” (RHCP). When multiple pilots are flying together, one using LHCP and the other with RHCP helps reduce interference.
LHCP antenna rejects signal from RHCP antenna and vice versa, and interference is reduced between the two VTX’s.
For the same reason, using CP antennas helps minimize multipath interference. Every time a signal bounces off the wall or ground, it changes the direction of polarization. For example, a bounced LHCP signal becomes RHCP which will be rejected by the receiving LHCP antenna.
For pilots flying in a group, it’s best to have 1 set of each LHCP and RHCP so you can use whatever you are required when racing. If you are just flying alone most of the time, then this doesn’t really matter, just buy RHCP since it’s more widely available.
Directional and Omni-directional Antennas
Another classification of FPV antennas is directionality:
As you could guess from the names, omni-directional antennas radiate their 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 Omnidirectional and the torch is directional. If both light sources are operating at the same power, torch can reach further but in the expense of narrower beam width.
Directional antennas can be linear polarized or circularly polarized, same as omni-directional antennas.
Omnidirectional antennas are great for every-day flying, and it provides good signal coverage all around the pilot. Try to avoid using only directional antennas so you don’t have to constantly turning yourself to face directly towards your copter.
However directional antennas are often used on diversity receivers, where it can be paired with an omni-directional, or multiple directional antennas to cover all the necessary angles.
Diversity receiver can receive two signals from two antennas instead of just one, and it can then choose to display the stronger signal.
For example, if you have a diversity setup with a CP antenna and a helical antenna, the receiver will switch to the helical antenna when flying in front and to the CP antenna when flying behind.
Antenna Performance Measurements
There are many antenna performance measurements regarding FPV antenna design, such as:
- Radiation Pattern
- Axial ratio
- Frequency bandwidth – a range of working frequency
- Tuned Frequency – what frequency is the antenna tuned to and would work the best
I mainly look at the first 2 or 3 factors when choosing my antennas. As long as you are buying your equipment from a name brand you shouldn’t worry too much about it. In my opinion we are not flying a rocket for NASA and there is no need to cause headache for yourself in this case :)
But if you want to find out more about these concepts, both antenna-theory.com and wikipedia are great resources for learning about antennas. In the following sections I will try to explain what gain is and what radiation pattern can be used for.
Gain is an indicator of directional antenna’s range and angle of coverage. Higher gain generally means further range but narrower beam width. Antenna gain can alter radiation pattern as we will see in a moment.
Tutorial: How antenna gain affects range?
Radiation pattern (radiation chart) shows the shape of the radiation emitted by the antenna. These charts can tell where the weak spots are and how likely it is to lose signal.
Here are some examples to help you visualize the the signal coverage patterns.
A 0dB gain antenna is truly omni-directional that has a nearly perfect spherical radiation pattern.
However omni-directional antennas in real life usually has signal loss on the top and bottom, and the radiation pattern would look more like a doughnut in 3D. In a two-dimensional view, it forms a figure-of-eight pattern in the vertical plane, and a circle in horizontal plane.
Here is the radiation pattern for an 8dB gain patch antenna. Notice the narrow beam width in both vertical and horizontal planes.
In reality there is no perfect circular polarized antenna. For example, a 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 practical FPV flying terms, this is the measurement of how susceptible the antenna is to multipath interference. The closer to 1, the better.
Types of Antennas
We have covered most of the basics in FPV antenna, and now I can finally introduce you some common types of antennas used for FPV.
|Linear Polarized||Monopole, Dipole||Patch|
|Circular Polarized||Cloverleaf, Skew-Planar Wheel, Pagoda||Helical, Patch, Crosshair|
Monopole antenna is the simplest form of antenna, which is basically just a piece of un-shielded wire. It’s very common in radio receivers because they are cheap and easy to repair. However they are not as effective as Dipole antennas. The length of the exposed wire is crucial as it determines the resonant frequency (frequency that it can pick up).
Tutorial: how to make Monopole antenna.
Dipole antennas relatively simple which is based on monopole antenna with a ground sleeve at under the active element which boosts the performance considerably. Dipole antennas are light weight, and can be made very durable against crashes. Nearly all video transmitters and receivers come with dipole antennas.
Cloverleaf and Skew-Planar Wheel 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 four lobes. These antennas are omni-directional like dipole. But they are circularly polarized and provide better reception and yet 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 housing.
Pagoda is a new antenna design that only became popular in late 2016. It’s an omnidirectional circular polarized antenna. The unique design and use of material (PCB) makes it very durable.
See our discussion on Pagoda antennas for more detail.
Helical antennas are spring-shaped, directional circular polarized antennas. The number of turns of coil determines the gain of the antenna. For more detail check out our article on Helical antenna and Patch antenna.
Patch antennas are also directional, and can be found in linear and circular polarization. They generally have less directionality than Helical, and smaller foot-print.
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 lower end 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.
After all, it all depends on what you can afford and your 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.
What Antennas For VTX and VRX
When buying FPV antennas in pair, normally they are interchangeable and can be used on either TX or RX. Otherwise, they should be clearly labelled “TX” and “RX” on the outside.
Antennas on VTX and VRX don’t have to be the same. Directional antennas are often used on VRX to get more range. While on the VTX you should always use omni-directional antennas, due to the fact that quadcopters can be in different orientation during flight.
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.
More recently “U.FL” connectors are becoming popular in VTX due to the light weight and compact size for mini quad.
A racing drone will inevitably experience many crashes during its life time. Since the antenna is installed on the outside of the frame, it will take no less abuse than the propellers and the frame. Therefore choose your antenna base on your likelihood of crashing. If you crash a lot, durability and robustness should be your priority in choosing FPV antenna.
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.
DIY FPV Antenna
Some of the antennas used in FPV actually can be made quite easily by yourself, at home. Although there is no guarantee in the performance, it’s definitely cost effective yet a fun way to learn about how antenna works :)
- My attempt at making cloverleaf antennas: https://oscarliang.com/make-diy-cloverleaf-antenna/
- Pagoda assembly video: https://www.youtube.com/watch?v=49rRR8iEiKc
- DIY Helical by IBCrazy: https://www.rcgroups.com/….Circularly-Polarized-Helical-antenna…
More to be added on a later date….
The Best FPV Antennas for Mini Quad
Here are 5 of the best FPV antennas picked by our multirotor community on Facebook (multicopter international) in April 2017.
As mentioned previously, the pagoda is a simple yet effective design. It’s made of cheaply available PCB and assembly is a lot easier than traditional cloverleaf antennas, which allows the the cost and price to drop significantly. The pagoda can be found at around $5 to $10 each making it one of the best value antenna out there.
There are a few different manufacturers for the Pagoda antenna, such as Lumenier, MenaceRC, Emax, Farview and Realacc.
Unlike the classic cloverleaf and skew planar wheel, the TBS Triumph does not use any bent wires in the element. The unique design provides more uniform signal coverage, makes it very durable as well as harder to clone.
Foxeer 3dB Omni CP
Foxeer makes some of the most affordable antennas in the market. Although they don’t have the best performance, they do have good enough quality for those who are on a budget to replace the stock Dipole’s.
These antennas are very durable thanks to the thick plastic housing, but it also takes the total weight to a heavy 12g.
The Lumenier Axii by GetFPV has a tiny diameter of only 16mm, which makes it one of the smallest and most durable CP antenna in this list. On paper it claims to have an excellent axial ratio, providing true circularity and is available in both RHCP and LHCP.
Aomway 4-lobe Cloverleaf
The Aomway 4-lobe’s are tried and tested antennas. They have been around for years and remain to be a good choice in terms of performance. However as you can see the antenna wires are fairly exposed and do not have plastic cover. So there is concern over robustness, although we are told the lobes are very strong and difficult to bend with the plastic reinforcement. There is now a new version that comes with plastic caps that protects the lobes.
So that covers some of basics and considerations in choosing your 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!