Antennas

Antennas are passive electrical devices that convert electromagnetic radiation into electrical signals, and vice versa. Both transmitters and receivers require antennas to operate. Transmitters typically have small “whip” antennas mounted on them, and receivers usually have a connector on the rear to attach an external antenna. There are a number of types of antennas commonly used for wireless microphone receivers.

Omnidirectional Antennas are best for situations where there is not much noise near the frequencies being used by the microphone systems. Noise is often reduced by buildings, distance from television transmitters, and antenna location (lower is better). It is worth noticg that while these antennas pick up signals equally well from alld irections, they typically respond better to signals polarized the same direction as the antenna (for example, if the antenna is mouted vertically, the bodypack antenna should also be vertical).

Directional Antennas, such as Yagi’s and Log Periodic Dipole Arrays (LPDAs), are better suited for noise environments. By their nature, they are directional and receive well toward their front, reducing or nulling noise toward their rear. Some LPDA’s designed for wireless microphone use include preamplifiers as well. One downside to these antennas is that they inherently receive signals polarized one way better than signals polarized perpendicularly to the antenna. Directional antennas wil also give increased range as they have forward gain.

Helical Antennas are directional antennas, but unlike LPDA’s and Yagis they are designed to receive signals of all polarizations equally well.

Antenna Distribution

In most wireless microphone systems, a single pair of antennas is used to receive the desired signals, and the output of these antennas is then split to all of the receivers.

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