FPV Quadcopter Part Spotlight: Video Antennas

This article focuses on analog video antennas for FPV. We cover what these antennas are, how they work, and how to choose the right one for your needs. Digital systems available don't come standard with replaceable antennas so we won't be covering them. Analog video systems are the most commonly used on micro and racing FPV drones.

For further reading, see the master article: Components & Anatomy of an FPV Quadcopter

Understanding Video Antennas

You'll find antennas attached to video receivers and transmitters. The transmitter is normally found on your quadcopter. The receiver is found on your goggles, screen, or ground station. Lets dive into the important aspects of these antennas.

Video Frequencies

Analog video systems are available in many frequencies. The most popular being 5.8GHz, 2.4GHz, and 1.3GHz with options down to 433MHz. The lower the Hz, the longer range the frequency supports. Almost all FPV racing quadcopters are going to be using 5.8GHz. The power output of your video transmitter also has an influence on the range of your video.

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The width of the frequency band is also important. The 5.8 band ranges from 5645 GHz to 5945 GHz.  This range holds 40 separate channels. A wide band is especially important for racing with multiple pilots in the air. 5.8GHz was enough to put 16 flyers in the air at the same time during the MultiGP 2016 Drone Racing Championship.

Main Point(s):

• Understanding frequencies is important. You will want to buy video antennas that support the frequency you're working in.

Antenna Polarization

Polarization of the signal is simply the way which the video signal travels out from the antenna. There are two types of polarization - linear and circular.

Linear Polarization

This type of signal transmission sends out a linear signal which oscillates either horizontally or vertically. Because of the flat nature of the output signal, this type of polarization is greatly effected by the orientation of the antenna. When the receiving and transmitting antennas are aligned, the signal strength is strong. The signal can travel great distances in this manner.

Dipole antennas transmit linear signal. These antennas are less than ideal for FPV flying because the orientation of your quadcopter constantly changes. They also suffer from multi-pathing which results in poor video quality due to the video signal bounces off objects.

Circular Polarization

This method of transmission sends out signal on both the horizontal and vertical axis' in a circular motion. This fits the needs of FPV pilots nicely because the orientation of a quadcopter constantly changes. Circular polarization keeps the video signal strong through these changes and helps prevent multi-pathing.

There are two types of circular polarization depending on the design of your antenna: Left Hand Circular Polarized (LHCP) and Right Hand Circular Polarized (RHCP). The difference between the two is simply in the way that the video signal rotates as it is transmitted. Your transmitter and receiver need to use the same direction of polarization rotation.

To go more in-depth on the topic of Polarization, Wikipedia has you covered.

Main Point(s):

• Linear polarization is preferred when the orientation of your craft does not change, and you intended to fly long range.
• Circular polarization is preferred when the orientation of your craft does change and is the most common type for FPV.
• You must match rotational polarization direction on the sending and receiving antennas.

Antenna Gain

The gain of an antenna is a measure of power of an antenna or video transmitter. This measurement is specified as the gain in dB. Video antennas have a gain rating that can help give a comparative idea of the range. The more directional the antenna, the higher the gain.

Types of FPV Video Antennas

In this section we cover the types of video antennas available on the market and the use for each. There are two main types of antennas and many designs within each type. The main difference between the two groups is the style of transmission. Omni-directional antennas send and receive video signal in a 360 degree area around the antenna. Directional antennas focus the signal path in a single direction to send and receive in a specific direction.

Omni antennas have a larger area of coverage, but less of a signal range due to lower gain. Directional antennas focus the area of coverage into a smaller area, but gain range and penetration due to higher gain. Omni-directional circular polarized antennas are almost exclusively the type of transmitting & receiving antenna you will find FPV pilots using. If you have a single antenna, you'll use an omni. If you're running a multi-antenna diversity setup, you may be running just directional or both directional and omni.

We have to give a shoutout to Alex aka IBCrazy at Video Aerial Systems who has been pioneering FPV antenna technology for a long time.

Omni-directional

Dipole

These antennas are simple linear polarized antennas. Inside the casing you'll find some coax cable with a metal casing on the end to send/receive signal. Dipole antennas are commonly included with transmitters and receivers, but are rarely used. One exception is the use of dipole whip antennas on micro FPV camera + VTX combos.

Skew Planar Wheel / Cloverleaf

These circular polarized antennas send video signal out via 3 or 4 lobes. 3 lobe antennas are referred to as skew-planar and 4 lobes are cloverleaf antennas. The two styles are often used in combination, one of each on the receiving vs transmitting ends.

It's common for manufacturers to encase these antennas in a hard plastic shell. This protects the antennas during crashes.

Directional

Patch

This antenna type comes in both linear and circular polarization. Recognizable by the square design, these antennas have a high gain for strong video signal. They are not as good at handling multi-pathing when compared to the helical design. The compact, high gain design is desirable and common on diversity setups.

Helical

These circular polarized antennas are compatible with 5.8GHz and 2.4GHz. They use a spiral design that improves gain and performance. The antenna is classed on the number of turns (spirals). As the number of turns increases, so does the length. Most FPV helical antennas are between 3 and 4 turns. In addition to the spiral, this antenna has sidelobes which help pick up some signal on the sides/behind the direction it's pointing.

Crosshair / Pepperbox

These circular polarized antennas use an X design held within a box to achieve an extremely high gain. This design lends itself to great quality in a focused area. You miss the side/behind reception you gain with a helical, but gain the directional signal. These antennas are great for diversity setups when combined with an circular polarized omni.

The pepperbox is an extension of the crosshair design by IBCrazy. It uses two crosshairs side-by-side to give you a larger horizontal angle of coverage.

Video Antenna Connectors: SMA vs RP-SMA

Manufacturers use two types of connectors on video antennas: SMA and RP-SMA. Performance wise there is no difference between the two. The difference only lies in the compatibility. Be sure to check that your antennas and receiver/transmitter are connecting properly. Nothing worse than finishing your first build only to find that your antenna doesn't fit one or the other.

This handy chart will help you as you shop and browse for antennas:

Here at Controller Craft we keep a curated list of video antennas for FPV.