Wireless Hacks, 2nd Edition

Appendix B. Wireless Hardware Guide

Hacking on 802.11 devices can come with a corresponding confusion factor. Why do you need a pigtail? Isn’t that what little girls wear? What on earth is LMR cable? Why do I need it? What is a RP-TNC connector, and where would I find one?

This appendix attempts to answer these questions and more, by discussing a number of common wireless hardware parts that you will run across.

Microwave Cabling

Not all coaxial cable is appropriate for 2.4 GHz use. The same cable that delivers high quality video and audio to your TV is nearly useless for connecting microwave antennas. Choosing the proper type and length of cable is just as important as choosing the right antenna for the job. A 12 dB sector antenna is useless if you lose 18 dB in the cable that connects it to the radio. While all cable introduces some loss as signal travels through it, some types of cable do better than others at 2.4 GHz.

LMR is a kind of coax cable made by Times Microwave, and is possibly the most popular type of cable used for extending 802.11b networks. LMR uses a braided outer shield and solid center conductor, and comes in various sizes.

Heliax is another kind of microwave cabling made by Andrew. It is made of a semi-rigid corrugated outer shell (a sort of flexible copper tubing), rather than the braided strands found in coax. The center conductor can either be solid or a corrugated tube inner conductor. It is designed to handle loads much greater than (legal) 802.11b installations, ...