The first thing to remember is that there is no such thing as a 'perfect' or 'best' coax cable, it will depend on what you want it for. Depending on what you need it to do, what power you use and what lengths you need will dictate which cable is 'perfect' or 'best'! However, for most amateurs there will be a compromise between price and efficiency.
Now the technical bits:
Coaxial cables are a form of signal transmission cable that is used to pass electrical signals between devices, systems, or components. Whereas standard electrical cable consists of one or more wires through which an electrical current is passed (a flow of electrons), coaxial cable is used to pass radio frequency (RF) signals in the form of a transverse electromagnetic wave. The design of coaxial cable consists of an inner conductor surrounded by a dielectric layer, which is then enclosed in a cylindrical sandwich that contains additional layers of shielding as well as an outer protective jacket to prevent damage to the signal carrying components during installation or from environmental stresses. Coaxial cables are commonly used as transmission lines and can transmit high-frequency signals at low loss.
The terms coaxial cables and coaxial cable assemblies are often used synonymously, however, some references differentiate the two by defining the assembly to represent the cable material fitted with end connectors and available in standardized lengths for immediate delivery. In that context, a coaxial cable would represent bulk cable sold in spools or coils of say 50 or 100 meter lengths, to which cable connectors are fitted once the final cable length has been established.
Coax (coaxial) cable is one of the oldest types of cables, having been in use for over 100 years. Like ethernet, coax cables come in both solid and stranded versions, although they are usually solid. Only a few types of coax, namely RG58 and RG8, are available as stranded.
Most coax cables fall into one of two categories, RG (Radio Guide) and LMR. No one is 100% sure what LMR actually stands for. It could stand for a term, someone’s name, or just be random letters. There are many rumors and theories for what LMR may mean but nobody really knows for sure.
RG cables are labeled “RG#” with the number formerly standing for the diameter of the cable. For example, RG59 cable originally had a diameter of .059”. While these measurements have changed over the years, the names of the cables have stuck. Typically, RG cables have a 50 or 75 ohm impedance. Some off-shoot cables have different impedance, but all the standard RG cables covered here will be one of those two.
LMR cables are labeled “LMR-#”, with the number being a rough estimate of the cable thickness. For example, LMR-400 has a 0.405” OD (outer diameter). LMR, like RG, has a few main types but off-shoot versions are also available. LMR is all 50 ohm cable (with one exception, covered below under LMR-400). Except for LMR-100, all the LMR cables are also made in UltraFlex versions for situations where extra flexibility is needed. Being newer than RG cable, LMR is better overall and most types of LMR cable were designed to replace specific RG cables.
RG Cables
RG58
RG58 is a common cable used for 50 ohm applications, measuring 20 AWG. Today it is mostly used on devices that need only audio or video instead of both, like a HAM radio or security camera.
RG8
RG8 is a thicker 50 ohm cable, at 12 AWG, that can provide a stronger signal than RG58. It is mainly used for amateur radio. There is also a version called RG8X, which is thinner at 16 AWG but provides similar signal quality.
RG59
RG59 is the 75 ohm alternative to RG58, also measuring 20 AWG. It used to be used for cable television but has largely been replaced by newer, more effective coax cables.
RG6
RG6 is the successor to RG59, measuring at 18 AWG. Also a 75 ohm cable, RG6 is better shielded and carries HD signals for greater distances. Currently, this is the standard cable used for cable television, satellite television, and cable internet modems.
RG11
RG11 is another 75 ohm cable that is thicker than RG6 at 14 AWG. The thickness makes it less flexible but ideal for long runs. It is commonly used in place of RG6 when distance is an issue.
RG174
RG174 is a thinner variant of 50 ohm cable at 26 AWG. Its thinness provides extra flexibility but signal loss is higher compared to RG58. This cable is most commonly used for Wi-Fi pigtails.
RG178
RG178 is also 50 ohm and used for high-frequency signals, with a maximum attenuation of 42.7 @ 900 MHz (almost double the max attenuation of RG174). This cable is very thin at 30 AWG, making it best for short distance runs.
RG316
RG316 is an alternative to RG178. RG316 is twice the size of RG178 at 26 AWG, giving it half the attenuation but also cutting down on signal loss.
LMR Cables
LMR-100
LMR-100 is very thin, being designed to replace RG-174. It possesses more than double the shielding of RG-174, cutting down on signal loss significantly.
LMR-195
LMR-195 was made as a replacement for RG58. With superior shielding, signal loss is decreased anywhere from 20% to 33% depending on the distance of the cable.
LMR-200
LMR-200 also replaces RG58 and has the same 0.195” OD as LMR-195 cable. The difference is that LMR-200 has a slightly thicker center conductor, allowing it to cut down on signal loss a bit better than LMR-195.
LMR-240
LMR-240 was made to replace RG8X. Signal loss using LMR-240 is 35% to 64% less than RG8X, with fluctuations depending on the overall distance the signal travels.
LMR-400
LMR-400 is arguably the most common LMR cable, being a replacement for RG8. There is also a version called LMR-400-75, the only LMR cable capable of running at 75 ohm.
LMR-600
LMR-600 was not made to act as a replacement to RG coax like the other LMR cables. Instead, it was built to be a very thick and powerful cable for long distance runs. LMR-600 is primarily used for powerful satellite frequency transmissions, being able to run signals from 100 to 500 feet.
The common specifications for coaxial cable include the following:
The cable type or RG type, (which stands for Radio Guide), now largely an obsolete reference given that the underlying standard which defined these terms is no longer an active document. RG-8 is a very common type used by Radio Amateurs. BTW no one is 100% sure what LMR actually stands for.
The material for the inner core conductor, which may be bare copper, silver-coated copper, tinned copper, or aluminum/copper, to name a few choices.
The impedance of the cable. The most common values for impedance are 50, 52, 75, or 93 ohms.
The jacket material, which is used as the outer protective layer of the cable.
The key cable dimensions, which include length, outer diameter, and wire gauge.
The desired connector configuration, which includes both the desired gender as well as the specific connector style such as BNC, SMA, SMB, or N-type.
The minimum bend radius
The attenuation measured in dB per unit length of cable
The rated temperature for the cable
Last Updated 2 April 2022
