Those Pesky Connectors

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Antennas typically have N connectors although Cisco antennae will most likely have a ReverseTNC to avoid Pigtails. Most APs and PCI-based NICs with external antenna jacks will have either RP-TNC or RP-BNC connectors, while most PC-card-based NICs don't have any connectors. The few that do (e.g. Lucent and Cisco) normally will have Lucent or RP-MMCX connectors (older devices may have MMCX connectors).

Use connectors sparingly. Each connector in a system introduces some loss, so try to avoid adapters and unnecessary connectors whenever possible. Try to buy cable with the proper connectors already attached, and, of course, use the shortest length possible, Wi-Fi equipment doesn't put out much power, and every little bit helps extend the AP's range and reliability.

Also bear in mind that when matching cables, you may encounter connectors of reverse polarity (male + female swapped, with same threads), reverse threading (left-hand instead of right-hand thread), or even reverse polarity reverse threading (both). Make sure you know what you're getting before you buy.

Note 

Ever wondered why WLAN cards have these annoying, special connectors? The FCC (and other regulatory agencies) is the culprit. Various regulatory agencies have requirements that unlicensed equipment be shipped with connectors "not available to the general public." The actual FCC rules—Part 15: Unlicensed RF Devices, Title 47 of the Code of Federal Regulations specifically 15.203—say that class licensed RF equipment must be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. Once hard-to-find connectors, like MMCX, become too popular, at least in the regulatory agency's opinion, they are banned as being too available to the general public.

Always check the connectors even when purchasing products from the same vendor. While some device families use the same type of connectors through their whole range (particularly those from same OEM - for example, Lucent is the same as Compaq), others change their connectors across their product families (for example Cisco offer two types of external connectors).

Figure 21.2: Examples of low loss, weatherproof, and phase-stability coaxial antenna cables. All of the depicted cabling feature 50 Ohm impedance for connecting between access point and 2.4 GHz antenna.

Figure 21.3: An example of the various types of connectors you might need when deploying a WLAN.

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