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Omni directional Wi-Fi antenna

In your opinion, will there ever be an omni directional Wi-Fi antenna that would span one mile or more? Will this antenna technology be affordable to small and medium business? When do you anticipate this antenna's general availability?
Omni

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directional (for example, "rubber ducky" dipole) antennas transmit in a 360-degree pattern, whereas directional antennas concentrate transmission in a given direction. Patch and panel directional antennas point signal on one direction, but still in a hemispherical pattern. Yagi and parabolic dish directional antennas obtain even greater ranges because they focus signal more narrowly.

For example, Cisco's AIR-ANT4941 is an indoor omni directional dipole antenna. According to product specs, it covers 130 feet at 11 Mbps or 350 feet at 1 Mbps. Cisco's AIR-ANT3549 is an indoor patch antenna that covers 200-700 feet when connected to an AP (point to multipoint). However, when connected to an indoor bridge (point to point), this same patch antenna can reach up to 2 miles at 1 Mps (3390 feet at 11 Mbps).

Greater ranges are usually achieved by outdoor bridge antennas. Cisco's AIR-ANT4121 is a high-gain mast-mount outdoor omni directional antenna that reaches up to 4.6 miles at 1 Mbps (1.4 miles at 11 Mbps). It can be used in either point-to-point or multipoint scenarios. In contrast, Cisco's AIR-ANT3338 is an outdoor point-to-point directional dish antenna that reaches up to 25 miles at 1 Mbps (11.5 miles at 11 Mbps).

These are just a few examples from Cisco's website (http://www.cisco.com/warp/public/cc/pd/witc/ao340ap/prodlit/airoa_ds.htm). They show that omni directional antennas already exist that span over one mile - under the right circumstances, in certain applications. Speed and distance are inversely related. And vendor specs reflect ideal conditions (no obstructions, short low-loss cables, etc). As for price - well of course this varies quite a bit. I've seen the AIR-ANT3549 patch antenna retailing for $165-190. The AIR-ANT4121 high-gain omni directional antenna is a good bit more expensive, retailing right now for $475-515. Antenna prices are dropping, and high gain omni directional antennas are becoming more widely available, but I really don't have any insight into when you'll see under-$100 antennas that span more than one mile (omni directional or otherwise.)

Another consideration: Directional antennas are more attractive from a security perspective, because they make it easier to contain transmissions within a building or single floor of a building. The less broadcast traffic that your antenna leaks outside to the parking lot or the office next door, the less likely you are to have wireless squatters borrowing your WLAN bandwidth for a free ride onto the Internet.

This was first published in December 2002

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