Wi-Fi Card Adapters
Wi-Fi, which stands for Wireless Fidelity, is a technology that any computer can use, from desktop to PDA. Since laptops are mobile and moved more often than desktops, it is more common for them to be equipped with Wi-Fi cards. Desktops can access the Internet through Ethernet cable connections, so they do not often come with wireless capabilities. However, most desktop computers do have several expansion slots you use to add new capabilities, such as Wi-Fi cards. A Wi-Fi card acts as an adapter, picking up the appropriate Wi-Fi signal and translating it for your computer. These cards either come with an antennae or use an antennae function already present on your desktop to search for wireless connectivity. If you are looking for a less expensive option, there are alternative types of adapters such as USB Wi-Fi adapters, which plug into a USB port on your computer, or adapters that use a land-line Ethernet connection to send information.
Picking up Wi-Fi Signals
When a Wi-Fi card is correctly installed, an option will appear on your desktop to let the adapter search for a nearby connection (often, this is set to happen automatically when the computer is turned on). In order to give you online access, the Wi-Fi adapter must be able to find a router or hub creating a Wi-Fi hotspot. Wi-Fi hotspots are areas where a local area network (LAN) is available, usually through a device that connects to the Internet via a cable and broadcasts the signal as radio waves. If there is no wireless LAN near your desktop, you can easily create one by buying a router and turning your land-line connection into a wireless network, although this is only useful if you have a second desktop or laptop computer. Wi-Fi hotspots are usually 300 to 400 feet wide. When the Internet service is paid for and your desktop computer picks up a viable Wi-Fi signal, several things happen. First, the adapter and the Wi-Fi hotspot must be able to communicate---there are several kinds of radio frequency formats Wi-Fi uses, known as a, b, g and n, and your adapter must be able to read at least one of those. Most adapters and networks broadcast in more than one format, so this is rarely a difficulty.
Alternative Wireless Connectivity for Desktops
In addition to providing Internet access this way, desktops can also pick up several other types of wireless activity. Certain phone companies, such as Sprint, offer a service that gives Internet access on their phone network, sending and receiving data through the same system they use to send voice information. This capability is available on 3G networks, and can be given to your desktop if you buy a 3G adapter instead of a Wi-Fi adapter. You must pay the phone company to use its 3G network, but you can then access the Internet wherever the company offers phone service. WiMAX is a service similar to Wi-Fi, but focuses on urban areas and a much wider broadcast range.
Security and Data
Wi-Fi networks are protected from outside access by layers of encryption and passwords. Your adapter sends packets of information back and forth from the Wi-Fi network with the correct password, and the network allows your computer to decrypt the data packets it sends. Once the security qualifications have been met, the two devices can communicate effectively and begin sending large numbers of data packets back and forth, giving you access to web browsers, email and other online applications on your desktop, just as an Ethernet connection would, often just as quickly, with only a few seconds of difference.