Wireless Hacks

Hack 66 Pigtails

Use a short length of feed line to connect your wireless device to an antenna.

While some wireless equipment has no external antenna connector available at all, many devices ship with a tiny, non-standard port to accommodate an external antenna. Most antennas use a standard microwave connector [Hack #63]. Typically, to connect one to the other, you need a short length of cable with one of each sort of connector. This connector is commonly referred to as a pigtail adapter. A pigtail in all its glory is depicted in Figure 4-29.

Figure 4-29. A Lucent pigtail with an N male end.

Pigtails are available from a number of sources. They typically sell for $10 to $20, depending on the length and type of cable, and what connectors you need on each end. Be sure that you know what sort of connector [Hack #65] you need on the card side as well as on the antenna side. Most 802.11 manufacturers will also sell you a pigtail adapter for a phenomenally inflated price ($80 to $100 or more, for virtually the same piece of cable).

Pigtails have extremely high loss compared to a larger cable (such as LMR400), and usually use a cable such as LMR100 or LMR195. It is generally a good idea to keep your pigtail lengths as short as possible, and run larger, lower-loss cable for the bulk of your antenna run. Be sure to observe the type of connector, as well as the gender (male or female) that you need for either end. Adapters and gender changers can help in a pinch, but remember that excessive adapters will add unnecessary loss to your overall system.

The client card end of a pigtail is typically available in straight or right-angle versions. Both connectors have identical loss, but the best choice depends on the physical layout of your equipment. Most times, a right-angle connector is preferred, but depending on how your cable needs to run, a straight connector may work better. Also remember that the small end of the pigtail is very fragile, and will snap easily if pulled or forced into the connector. Use care when installing or removing pigtails, and whenever possible, tie off the cable to help eliminate cable stress on the connector. It is common to use a nylon zip tie to fasten the cable to the card itself, the chassis, or another stationary part.

When you are sure of the sort of pigtail you need for your application, consult the list of hardware vendors [Hack #67].