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What is the Difference Between an
Omni Directional and a Directional Sector Antenna?

    Different Types of Wireless Antennas

    Because the radio equipment used in wireless networking must by law be very low-powered to minimize interference with other devices, the antennas required are much more focused than those used in radio or television applications. The amount of focus they use in transmitting a signal, and their corresponding ability to "pick out" specific radio signals is called gain. The gain is measured in decibels, abbreviated dB.

    Sector Wireless Antennas

    There are two major categories of antennas: directional and omni-directional. Directional antennas focus their energy in tight, narrow beams. When receiving signals, directional antennas do not "see" any signals coming from outside the "beam" on which they are focused. This eliminates a great deal of potential interference from other radio sources and contributes to the ability of multiple wireless communications systems to coexist with a minimum of interference.

    Omni Directional Wireless Antennas

    Omni-directional antennas transmit their energy in a full circle. Spreading the radio signal over such a large area reduces the energy in the signal. This severely restricts the distance the signal can be transmitted and received effectively. Therefore, transmissions via an omni-directional antenna do not travel as far before being degraded as do those from directional antennas. (However, amplifiers are available for both types of antennas to lengthen the transmit distance.)

    These characteristics make each type of antenna optimal in different situations. For those networks involving more than two buildings, called multi-point connections, an omni-directional antenna at the central site will be most cost-effective. A directional antenna is installed at each remote site, aimed back at the central site omni-directional antenna. Since the omni-directional antenna transmits in all directions, every remote antenna can pick up its signal and transmit back to it.

    On the other hand, some network connections involve only two distinct buildings. These are called point-to-point connections. In these situations, a directional antenna is used at each site, each aimed at the other.

    Both types of antennas are available with various levels of gain. BWE's Antenna Buyer's Guides shows some common antenna types, their gain, the maximum distance over which they are effective, and their approximate cost.

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