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As you know, wireless networks are all around us.Their main purpose is to remove the restrictions imposed by the cables. Due to lower prices, wireless equipment becomes more accessible to people who want to build thier own wireless networks. There are also thousands of public Wi-Fi hotspots around the world, through which you can access the internet wherever you are. However, in order to connect to any wireless network, your compuiter must be equipped with a wireless (WLAN) LAN card. That’s why in this post I will try to describe the different types of WLAN cards, to help you when choosing a wireless card for your computer.

1. PCMCIA cards

PCMCIA cards (or “PC cards” as they are sometimes called) are mainly used in laptops. They require a notebook equipped with an Type II card slot.The card contains both the 802.11 radio and antenna mounted together in one device.These cards are more expensive than their USB and PCI counterparts, but due to their wide proliferation, they can often be picked up for as low as $10 to $20.
There are only few variations of these cards, as they are fairly standard in design among the various vendors.The only real difference may be the chipset used for the 802.11 radio.The major manufacturers of wireless chipsets are Atheros, Broadcom, and TI (Texas Instruments).Most Original Equipment Manufacturers (OEMs) only provide software and drivers for Windows and Mac operating systems in the packaging. However, if you search the Web, you can often find additional drivers for Linux, BSD, and UNIX.
As you can see in picture, the antenna (the black part at the top of the card) extends out about an inch from the card.This design offers better reception than if the antenna were buried inside the card.The problem here is that the antenna is now vertically polarized so that the best received signals are those with vertical polarization.To compensate this design flaw, some card manufacturers allow connection of an external antenna in order to increase the performance.

2. Mini-PCI Cards.

Mini-PCI cards are very similar to PCMCIA cards in design except the lack of integrated antenna and protective outer shell. These cards are designed for newer laptops that often have the antenna wiring built into the notebook behind the LCD screen. Because the antenna is behind the LCD screen, your cards will have a better horizontal orientation and often have better reception than their PCMCIA counterparts have. In order to install such type of card your laptop must have a free Mini-PCI slot. Most mini-PCI slots are located on the bottom of the laptop under an accessible plastic or metal cover  similar to one that covers the memory or the hard disk. However, sometimes due to design constraints, we have seen manufacturers place mini-PCI slots under the keyboard, which requires a little more skills and to access. Mini-PCI cards are more fragile than PCMCIA cards and are not designed to be removed and installed often. However, they are also very versatile, as you can upgrade your notebook’s wireless card down the road and not have to worry about taking up a PCMCIA slot or accidentally damaging the built-in antennas of those protruding cards.

3. Mini PCI Express cards.

Mini PCI Express is a replacement for the Mini PCI standard used in many portable computers. Most laptops built after 2005 are based on PCI Express and can have several Mini PCI Express Card slots. The PCI Express Mini Card is half the size of the Mini PCI card. The physical dimensions of Mini PCI Express cards are 30?50.95 mm.There is also a 52 pin edge connector ( compared with Mini- PCI which has 124 pin connector ).

4. PCI cards.

PCI cards for desktop computers have come a long way in the past couple of years. Originally, they were implemented as a PCI-to-PCMCIA adapters that allowed you to insert a PCMCIA card into the back of your computer.The problem here is that the antenna was again forced into a location that suffered from poor reception. Most people tend to have their computers under a desk or behind a cabinet door, which is not a good place to locate the wireless antenna. In other words in this situation you’re placing the computer case or large amounts of wood which could be the desk between the radio and the AP.The signal will penetrate, but may lose some of its strength.That’s why some manufacturers started to make PCMCIA cards with removable antennas to help alleviate some of this problem.Today, most PCI cards actually have the 802.11 radio built into the card instead of using a separate PCMCIA package.

As you can see in picture, modern cards tend to have more powerful detachable antennas that can increase your reception. Some companies such as D-Link and Linksys sell slightly more powerful omnidirectional and unidirectional antennas to increase performance and allow more flexibility in antenna placement.