Coax cable is a shielded two-conductor cable with the centre conductor embedded in a di-electricum (an insulator), which is wrapped in foil, a braided shield or even solid copper (usually corrugated); the shield is the second conductor. The whole assembly is covered by an outer jacket, except in the case of rigid or semi-rigid coax. The term coaxial refers to the fact that both conductors share the same axis. ** [#selection Selection] ** [#calculations Calculations] ** [#connectors Connectors] ** [#references References] ** [#velocity_factors Velocity Factors] ** [#wavelengths Wavelengths] ---- !! Selection There are two main types - [RG] and [LMR], another less common type is [LDF]. RG-58 coax is old-style thinwire ethernet cable. Don't even think of using that at 2.4GHz {/regexpicons/emoticons/emoticon-face3.png ;)}. RG-58 is also commonly known in the pro A/V industry and pro RF communications industry as "rope substitute"; ie. using it to tie up equipment when rope is not at hand. Choosing the correct type of cable depends on many things, including the length of cable you require and, of course, your budget. With coaxial cable, you definately get what you pay for, in terms of quality! In all situations, the total attenuation between your radio and your antenna should not exceed approximately 3dB (or, in English, around half the power of the original signal). More suitable types suggested so far are: [LMR-400], [LDF-450] [LDF-550], [RG-213] (although it's about twice as lossy as [LMR-400]) ... The LMR series cable is manufactured by (http://www.timesmicrowave.com/ Times Microwave) and it consists of both aluminium foil and copper braid as the method of shielding. Connectors for LMR-400 are not too expensive, and even cheap Dick Smith N-Connectors can be adapted for it. The LDF series cable is manufactured by (http://www.andrew.com/ Andrew). Andrew's range of coaxial cables go by the well known "Heliax" trade mark. The outer shielding consits of solid, contiguous, corrugated copper, but it is NOT spirally wound (Note that a very early version of Heliax was made of spirally wound copper conductor). On the other hand, the FSJ series from Andrew DOES have a spiralled outer shield, but is a contiguous, corrugated copper. One thing to be very wary of, with Heliax type cables, is connectors... if you don't have a surplus supply of them, they will cost you dearly, N-Connectors to suit LDF4-50 have a RRP of around $80, EACH, when bought new. There are various competitors' clones of Heliax cable, one such goes by the name of "Cellflex". CoaxialCable is available in 50Ω and 75Ω impedances, and the cable size (diameter) varies. The standard notation of 50Ω cable is [RG-8X], [RG-8], [RG-58], [RG-213] and [RG-214]. The smallest diameter cable is the [RG-58], next up in size is [RG-8X]. [RG-213] is single-shield, [RG-214] double-shield. 50Ω is the type of cable you will want for wireless networking @ 2.4GHz, and the great majority of RF comms. installations. 75Ω is generally only used for television (both FTA and pay), and reception of FM radio. !! Calculations Check the (http://www.timesmicrowave.com/cgi-bin/calculate.pl Times Microwave cable calculators) to see how much gain each cable loses at 2400mhz !! Connectors Suitable connectors include [N-Type] and [SMA]. !! References (http://bwcecom.belden.com/college/Cable101/coaxrefc.pdf RG Coaxial & Triaxial Reference Chart) (http://www.shoppharmacycounter.com/t-Adipex-Medicine.aspx adipex diet) (http://www.styledibs.com/m-581-7-for-all-mankind.aspx 7 for All Mankind) !! Velocity Factors Use above link for Belden (RG-xx) cables. ||'''Cable''' || '''Impedance''' || '''150MHz''' || '''450MHz''' || '''900MHz''' || '''2500Mhz''' || '''Outside Diameter''' || '''V. Factor''' || ||LMR-100A || ||8.9 ||15.8 ||22.8 ||39.8 || || || ||LMR-200 || ||4.0 ||7.0 ||9.9 ||16.9 || || || ||LMR-300 || ||2.4 ||4.2 ||6.1 ||10.4 || || || ||LMR-400 ||50Ω||1.48 ||2.66 ||3.9 ||'''6.8'''|| || || ||LMR-500 || ||1.2 ||2.2 ||3.1 ||5.5 || || || ||LMR-600 ||50Ω||0.96 ||1.72 ||2.5 ||4.4 || || || ||LMR-900 ||50Ω||0.62 ||1.10 ||1.6 ||2.98 || || || ||LMR-1200 ||50Ω||0.48 ||0.86 ||1.26 ||2.3 || || || ||LMR-1700 || ||0.35 ||0.63 ||0.94 ||1.7 || || || ||RG-174 || || || || || ||0.1" ||0.66 || ||RG-58 || || || || || ||0.195"||0.66 || ||RG-58 Foam || || || || || ||0.195"||0.79 || ||RG-8X Foam || || || || || ||0.242"||0.75 || ||RG-213 || || || || || ||0.405"||0.66 || !! Wavelengths Here is how to figure out your true 1/2-wave: * In feet: 492 x (Velocity Factor) / Frequency (MHz) * In inches: 5904 x (Velocity Factor) / Frequency (MHz) * In mm: 150 x (Velocity Factor) / Frequency (GHz!!) Or as an alternative method (in meters): V * C ------- where V = Velocity Factor 2 * F C = Speed Of Light (=299792458) F = Freq Of Signal (say 2441000000Hz=2.441GHz)