The Drone FPV Antenna is perhaps the most overlooked FPV component.
However, without antennas wireless communication between the video transmitter
and video receiver or radio and radio receiver would not be conceivably possible.
This article will serve to outline the function of an antenna as well as the properties
of different antenna types.


What is a Drone FPV Antenna and how does it work?
An antenna is effectively a transducer; a device that transforms electrical energy
into electromagnetic radiation such as radio waves. When an electrical current is passed
through a wire a magnetic field is produced around the wire. In two closely approximated
wires carrying oppositely charged currents, the magnetic fields will be opposed and will
essentially cancel each other out. However, if the orientation of these positive and
negative wires is correctly manipulated, they will be capable of successfully propagating
electromagnetic radiation in the form of radio waves. In essence, this is an antenna.

There is no particular difference between a transmitting antenna and a receiving antenna,
any antenna may be used for either purpose. However, appropriateness of the antenna
selection should be carefully considered. Antenna suitability will be discussed later in the article.


Frequency
Antennas used in FPV are always tuned to a particular radio frequency.
The two most commonly used frequencies in FPV are 2.4GHz and 5.8GHz, for radio
link and video link respectively. Hertz (unit: Hz) is a measure of how many wavelengths
a wave oscillates through in one second. Picture a slinky being stretched out and rapidly
shook from left to right. Portions of the slinky will periodically mirror this shaking action
as it moves along the length of the slinky, rising and falling before repeating the cycle again.

The distance between a pair of crests and peaks is a singular wavelength.
Lower radio frequencies for radio control and video transmission,
such as 915MHz are often used when long range flight is a priority.


Directional and Omnidirectional Antennas
he different types of Drone FPV Antenna radiation patterns can be divided into two
categories based on the directivity of the beam; directional and omnidirectional.

Directional antennas are optimized for beaming a signal over long distances and in
a very specific direction. Omnidirectional, as the name suggests, are best suited for
the radiation of a radio signal in as many directions as possible, but over a relatively
shorter range.

The radiation pattern of the directional antenna can be pictured as being conical,
the point of the cone originating at the antenna. As the cone projects from the antenna
it gradually widens, before eventually coming to an end. Any object within the range
of this cone will be capable of receiving the transmitted signal, or transmitting its
own signal to the receiving antenna. Directional antennas are best suited for
receiver-side applications, where they can be positioned to allow optimal reception
of the signal transmitted by the video transmitter. As for omnidirectional antennas,
their evenly distributed radiation pattern is shaped as if a donut has been slid over
the top of the antenna, the active site of the antenna surrounded by the donut.

The radiation pattern of an omnidirectional antenna can be clearly pictured as being
particularly well dispersed in all directions around the antenna except directly above
and below the antenna. An omnidirectional antenna is typically used with the video
transmitter, as the omnidirectional antenna is well adapted to overcoming sudden
changes in the attitude and direction of an aircraft’s flight.

Monopole
The monopole antenna consists of a singular straight wire which is typically mounted
perpendicular relative to the ground. The monopole is a type of omnidirectional antenna
and is linearly polarized. The monopole antenna is commonly used in the radio transmitter
and radio receiver. Occasionally, the monopole is used in conjunction with a video transmitter
in micro size multicopters, as its low profile and light weight is favourable for racing applications.

Antenna Diversity
With antenna diversity two antennas can be used synchronously to achieve higher quality
and more reliable signal reception. For example, a directional linearly polarized antenna and
circularly polarized omnidirectional antenna may be used in tandem to effectively obtain greater
range in a certain direction while maintaining reception if the quad is to pass out of range
of the directional antenna.