In general, any VHF antenna is suitable for receiving AIS signals, as they typically cover the frequency range from 30 to 300 MHz. Other antennas are also suitable if they include the AIS frequencies around 162 MHz. Ideally, antennas are well-tuned for AIS to ensure a good reception range.

The higher the installed antenna, the greater the range. This is because the transmitting antenna must be visible to the receiving antenna, as the propagation of signals in the VHF range is largely line-of-sight. To achieve optimal coverage, the antenna should ideally be installed directly on the coast with an unobstructed view of the sea. This ensures that the antenna is free from interference from obstacles and provides the best possible signal reception range.

The Gain of an antenna measures how effectively it focuses electromagnetic waves in a specific direction. A higher gain means better signal concentration and range, typically measured in decibels (dB).

The Polarization of an antenna describes the orientation of the electric field of the electromagnetic waves radiated by the antenna. There are different types of polarization, and choosing the right polarization (horizontal, vertical, or circular) is crucial for the effectiveness of signal transmission and reception.

There are many different types of antennas, but for receiving AIS signals, dipole antennas and directional antennas are particularly well-suited. We will discuss these two types in more detail below.

Omnidirectional antennas are designed to receive signals from all directions, making them ideal for applications where the source of the incoming signal can come from any angle (360°). These antennas are particularly useful for covering large areas, as they can capture signals regardless of the transmitter's position relative to the antenna.

For optimal performance, it is crucial that the antenna is installed in an upright position. Installing it horizontally or lying flat can significantly reduce its effectiveness and ability to receive signals from all directions.

A Yagi antenna is a specific type of directional antenna known for its ability to receive signals from a particular direction in which it is aimed. A directional antenna receives signals within a cone-shaped area extending to the left and right of its aimed direction.

Properly aligning the antenna with the signal source is crucial for strong, high-quality signal reception. Understanding the width of the antenna's reception cone can help ensure optimal alignment.

This allows for the reception of distant ships and helps optimize a station's range, especially in areas where ships can only be received from a specific direction.

For AIS applications, the directional antenna should be vertically polarized to match the orientation of the signal. As shown in the picture below.

The location where you plan to install your AIS receiving station can significantly influence the choice of antenna type that best suits your needs. In brief, Yagi antennas require more precise alignment but offer long-range reception, making them ideal for targeting signals from a specific direction. On the other hand, omnidirectional antennas provide broad coverage and can receive signals from any direction, though their range is generally more limited.

As a general guideline, choose a Yagi antenna if your goal is to enhance signal reception from a particular direction. Opt for an omnidirectional antenna if you are in an area surrounded by water and need to capture signals coming from all directions.