What is the best WiFi antenna for me?

The single most important thing you can do to extend the range of your 802.11 system is to install an external antenna with some good gain and directional or omni-directional qualities. WiFi is simply a radio, which is used for computer. You can think of your antenna as the "speaker system" of your WiFi card. Get a bigger antenna; your WiFi will go a lot further. However, don't install a speaker on your wifi system or your range will be horrible!

Directional Antennas  

Directional antennas are used for Point-to-Point or sometimes for Multi-Point systems depending on the setup. If you are trying to go from one location (say for instance your router), to another location, this is the type of antenna we recommend. Directional antennas are Backfires, Yagi, Panel and dish type antennas.

Omni-Directional

This is the common "Base" antenna used for Point-to-Multi-Point or can be an omni-directional antenna for your car. An Omni-Directional antenna would serve as your main antenna to distribute the signal to other computers or devices (such as wireless printers, PDAs, etc) in your workgroup. You can use 2 Omni-Directional antennas for a point to point system, but this is usually not recommended because there is no real point to distributing your signal all over the place when you only want to going from point A to point B. Please refer to Directional antennas above. Typical Omni-Directional WiFi antennas consist of Vertical Omnis, Ceiling Domes, Rubber ducks, Small Desktops and Mobile vertical antennas.

Point-to-Point

Point-to-Point systems usually involve 2 different wireless points, or building to building wireless connections. But there are exceptions to every rule. If the access point is across a long valley and the owner of the system wishes to share the connection with multiple users on the other side of the valley. This would be a point to Multi-Point system but using directional antennas.

Point to Multi-Point

Point to Multi-Point systems is usually for sharing a WLAN (Wireless Local Area Network) or a high-speed internet connection inside of your home or with neighbors (oops, we didn't say that). They can also be for WAP (Wireless Access Points) such as you find at local coffee shops, truck stops, airports, RV parks and the ever expanding list of WAPs becoming available. Traveling with a notebook computer is extremely fun and can be a great business tool for the frequent traveler.

Range

The range of the signal will depend on several factors, including power output of your wireless card or router, receive strength of the wireless card or cards you are transmitting to, obstructions buildings or trees which may be in the way of your transmitting path, walls, etc. Since there are so many factors which can determine the overall range of your wireless system, it is impossible to cover it in this simple article. A rule of thumb however is to always choose an antenna which you think may be overkill. Why? Because the power output is extremely small it is necessary to have as much gain as possible. Most wireless cards have a power output of 32 milliwatts (+15dBm), which is roughly the same amount of power it takes to light a high power LED (Light Emitting Diode). LEDs are bright, but imaging trying to see one at a large distance or through a building or trees. This is why the antenna is critical for amplifying that signal so it is as strong as possible. Why is the power output so small? Because 802.11 works at the same frequency as a microwave oven (2.4 GHz) and if it put out a large amount of power…. well, enough said. Microwave popcorn! If you are somewhat technical, please visit our online wifi range calculator to learn more. 

One of our most frequently asked questions is how to choose the correct WiFi antenna for a particular situation. This can be either very simple or very complex depending on your particular application or what you need to do. 802.11b (11 Mbps) and 802.11g (56 Mbps) (Mbps stands for megabits per second and is a measure of bandwidth) standards provide excellent speed, but this completely depends on your signal strength and noise level of your wireless card and wireless system. This basically equates to, the larger the signal strength and the less noise your wireless card receives, the better.

There are many uses for wireless applications, either in a home, office or rural situations. Let's examine each of these applications.

Home

Home antennas are always the easiest types of antennas to purchase and take the least amount of effort in choosing and installing. In most circumstances, only one antenna is needed on the remote computer. We recommend putting any external antenna on the remote computer, simply because if you install it on your router and don't plan on setting up security, it will provide less signal strength outside of your home and your system will be less prone to hackers. If you have a multi-story home or a very large house, you may have to install antennas on every computer to get the range or bandwidth required. Every wall that you have to penetrate will decrease the signal strength of your system. For the best signal strength and signal, we recommend installing a 5dB ceiling dome antenna and either wireless desktop antennas or RL-1000 antennas on all remote computers. It is best to start with 1 antenna on a remote computer and test the signal strength and range.

Office

Office antennas are pretty straight forward. If you want to run a network system inside of your office building and don't want to run cables all over the place, first, purchase a good wireless card, install a Ceiling Dome, Desktop or Wibberduck antenna to extend and maximize the signal to your office router. It's that simple. However, this can get a little complex if the office is split between 2 different points or if the office is really large or on multiple stories of a building.

Mobile WiFi antennas

Why would anyone want WiFi in their car? Well, there are a lot of truck-stops and RV parks around the country now that offer wireless access. In fact, many public high speed wireless networks can be accessed directly from your car, truck, or RV. There is also something called WarDriving which is where bad people drive around neighborhoods and get their high-speed access for free. We don't condone this, but if you want to read more about it, please go to www.wardriving.com. It's fun and entertaining reading.

Yagi Antennas

Yagi antennas were the design of two Japanese people, Hidetsugu Yagi and Shintaro Uda, and are sometimes referred to as Yagi-Uda antennas. They were originally designed for radio, but are now also used for 802.11 systems. These antennas are typically very directional and are used for point to point, or to extend the range of a point to multi-point system. We highly recommend using the RadioLabs 14 or 16 element weatherproof Yagi antenna if you want to install your system outside. They have excellent signal strength and in the right circumstances can communicate for miles!

Backfire antennas 

The backfire is a small directional antenna with excellent gain. They look similar to a parabolic dish, but the gain isn't as high. We highly recommend Backfire antennas for point to point or point to multipoint systems because of the excellent gain and the good noise figures. We offer a backfire antenna with 15 dBi of Gain!! This is excellent considering the antenna is only 10 inches diameter.

Parabolic or dish antennas

This is where the real power is! Parabolic dish antennas put out tremendous gain but are a little hard to point and make a connection with. As the gain of an antenna increases, the antenna's radiation pattern decreases until you have a very little window to point or aim your dish correctly. Dish antennas are almost always used for a point to point system for long haul systems. The Parabolic Dish antennas work by focusing the power to a central point and beaming the radio's signal to a specific area, kind of like the adjustable reflector on a flashlight. These antennas are highly focused and are the perfect tool if you want to send your signal a very long distance. To calculate the distance of your WiFi...... WiFi Range Calculator or please call us for advise.

Gain Considerations

The gain you will require for each individual WiFi antenna system will dependant on any direct objects in your path, the distance you must cover and the individual wifi cards. These all must be taken into consideration before choosing the proper antenna system. If our calculator is too difficult to use, please feel free to contact us for information.

Interference

As with all radio systems, interference is always a problem. If you are listening to an AM radio and you hear static, this is interference. The same thing applies to WiFi systems, however not to such a large degree. Things that cause interference with WiFi systems are Microwave ovens, certain lighting systems, other 802.11 access points or systems, microwave transmitters, even high speed processors for computers can cause interference for 802.11 systems. All these problems must be isolated before you can expect any significant range out of your system. If you need help, please don't be afraid to ask us. Afterall, WiFi is our business.

Hernández Caballero Indiana
Asignatura: CRF
Fuente:http://radiolabs.com/Articles/wifi-antenna.html