Introduction
"Point all the antennas on the router at the smartphone and the phone signal will be strongest." If you think that, you are mistaken. This article explains basic antenna principles and practical placement tips so you can get better wireless coverage in crowded environments.
Common Misconception: Straightening Antennas for Directionality
Recently, a technical explainer video caused debate because the presenter straightened a router antenna to try to create a directional radiation effect. The assumption was that bending the antenna changes its radiation pattern to be more directional. That is not correct in the way many expect.
What Is an Antenna?
An antenna is familiar to anyone working with wireless systems. Its purpose is to transmit and receive radio waves. More precisely, an antenna is a converter that transforms a guided wave on a transmission line into an electromagnetic wave that propagates in free space, or vice versa.
How Antennas Radiate
From basic physics: two parallel conductors carrying alternating current generate electromagnetic radiation. When the conductors are close, the radiation is weak because opposing current directions induce fields that cancel. When the conductors are spread apart, radiation increases because the induced fields add coherently. When the conductor length reaches about a quarter wavelength, the radiation becomes significant.
Changing currents produce changing electric fields; changing electric fields produce changing magnetic fields, and the cycle continues to form electromagnetic waves. The two driven conductors that produce the field are called radiators or driven elements.
Radiator and Antenna Forms
A simple example of a radiator is a half-wave symmetric element formed by two metal plates or rods. This is only one of many radiator shapes; the radiator is the core element of an antenna, but a complete antenna can take many forms. Sometimes an antenna has a radome that conceals the actual radiator, which can lead to misconceptions about the true shape of the antenna element.
Common antenna types by form include whip antennas, parabolic reflectors, and Yagi antennas. The typical router antenna shown in the introductory video is a vertical monopole or whip-style antenna, which is an omnidirectional radiator.
Radiation Pattern of a Vertical Whip Antenna
The radiation pattern of a vertical whip antenna clarifies how it transmits energy: the signal radiates outward around the vertical rod, perpendicular to the antenna axis. In technical terms, the radiation is minimal along the antenna axis and maximal in the plane normal to the axis. In other words, the signal from the top of the antenna is weaker than the signal from the sides.
Placement Recommendations
To maximize coverage from a vertical whip-style router antenna, position the antenna vertically so the main lobes extend horizontally outward around the antenna. For home routers, this generally means keeping antennas in the upright position.
If antennas are laid horizontally, the main radiation plane rotates accordingly, which may reduce signal strength to devices intended to be served by the antenna orientation. Pointing the antenna directly at a device is not an effective strategy for this antenna type; it often results in weaker reception.
If the router is placed significantly higher or lower than the target devices, adjusting the antenna angle slightly can help shape the coverage to better reach those devices.
Practical Rules of Thumb
- Placing a pull-tab can over an antenna to boost signal is a common myth. It does not increase antenna gain in a meaningful way.
- Keep antennas spaced apart. Antennas that are too close can couple and interfere with each other.
- More router antennas do not necessarily mean better performance for a single device. Different antennas or antenna ports may serve different frequency bands (for example 2.4 GHz and 5 GHz). A device's supported MIMO configuration is limited, commonly 2x2 or 4x4, so a device cannot use more spatial streams just because the router has many antennas. Many antennas on a router can also be intended to support more simultaneous client connections rather than to increase throughput for a single client.
That covers the key points on antenna fundamentals and placement.
