Why Are Antennas Necessary?

If a device transmits or receives, an antenna is necessary.

An antenna is a device that transduces changes in current into electromagnetic radiation and vice versa. We obviously do not need an antenna in devices that neither transmit nor receive. However, the number of electrical devices that do neither is surprisingly small.

Why Add an Antenna?

It is possible for a device to transmit or receive just fine without an antenna at all. As an example, many times you can pick up RF interference on a radio. If a battery charger is unplugged or a lightbulb is switched off, the interference will disappear. This type of interference is being transmitted, yet it is apparent that the source of this annoyance is not intentionally equipped with an antenna. The secret is that something in the interfering device acts as the antenna — perhaps merely a length of wire.

It seems reasonable to wonder, then, if a device can transmit without an antenna, why have a discrete antenna at all? The answer to this question, in a nutshell, is to optimize performance.

To achieve good, solid, reliable performance, you typically need an antenna designed with the application in mind. The efficiency of an impromptu antenna is likely to be very poor — in the case of a transmitter, most of the power will be reflected back into the device. This power is burned up as heat, which, besides being a waste, can also damage something.

Even as a receiver, this setup is likely to be very insensitive. And, in both cases, the odds are the energy is radiating in a pattern that will be unsuitable for the application.

It is usually impossible to obtain satisfactory results without designing or using a discrete antenna with the application in mind.

Advantage: Antenna

Any device that transmits or receives, no matter what the range is, has an antenna of some sort, even if it is something not intended to act as an antenna.

To achieve best results, a discrete antenna designed for the application will provide the best performance. The parameters of the antenna will depend on the function of the device and the specifications the device must meet.