Almost any wireless network antenna will increase your range over not using one at all. Almost all wireless cards and routers are built so that external antennas can be easily attached. However there are a lot of things to pay attention to. There are different types and various metrics to measure them. To make it worse, there are different types of connections between the card jack and the cord.
The terminology can be confusing but most terms refer to things that are standard and the only one available. The current standard used for virtually all wireless laptops is the IEEE 802.11G WiFi standard. This operates at 2.4 GHz which is the only frequency used. Depending on signal strength and quality the connection is made at a set of assorted preset rates measured in Mbs getting gradually slower with worse connection quality. The speed is automatically selected as the best possible. The previous standard was 802.11B (proceeded by 802.11A) which the G standard equipment is backwards compatible with. Equipment that is merely built to the B standard is very old and hard to find. Bluetooth is a wireless technology for peripherals not used for communication between a laptop and any type of network.
The first major thing to consider is a directional vs. an omnidirectional (every direction) antenna. Simply put antennas can be designed to get better reception (and transmission strength) in one direction or from every direction. How small of an area it gets better reception from is a design factor. Directional antennas get better reception within the target angles than an omnidirectional one. Unfortunately how much is gained by making it directional is done at the expense of signal strength from other angles. In other words the average signal strength from every direction is the same regardless of if or how it is designed. Exactly how directional the receiver happens to be is measured by gain. Gain is how much signal strength is improved my making it directional. Gain is measured in decibels (dBi) which uses a logarithmic scale meaning that a small increase in the number is still significant. Most have some gain as there is usually little need to get a connection from above or bellow the antenna and omnidirectional antennas on the market really aren’t quite truly omnidirectional. The access point is almost always fairly horizontal from the antenna, not vertical. The higher the gain is the greater the need is to point it exactly at the source. Lower gain antennas (<10 dBi) usually don’t need to be pointed at the transmitter (access point).
Antennas also have a polarity, either vertical or horizontal. This refers to if the signal going out is polarized in the vertical or horizontal direction. If this matches there will be significantly better reception than if there is a mismatch. Most are vertically polarized, but turning the antenna 90 degrees onto its side will change the polarity.
The impedance is a measurement of how much the antenna its self reduces the signal strength. Smaller is better, and cord length increases this somewhat. Impedance is measured in Ohms, a unit of electrical resistance. Standing wave ration (SWR) also impacts the effectiveness of the wireless antennas. The SWR of 1:1 is perfect but unattainable. The last and most important feature is the connector type. The connector type is simply the standard of connection between the wireless card and the cord. This varies by manufacturer. The one you buy must have the same connection type as your card or wireless gateway.
We are sure that our prices are the lowest with the largest selection, but if you cannot find the exact antenna you are looking for there are some antennas from ShoppersChoice.com and from major online retailer Buy.com.