Difference between revisions of "Two Way Radio Antenna Cable"

Latest revision as of 18:52, 17 November 2015

RG (Radio Guide) is a military term. The RG series was originally used to specify the types of coax cables for military use. The presence of the letter U supposedly indicated it was for multiple uses. All current RG specifications are based on this obsolete military designation and the current specifications are very loose. You can just about give a coat hanger stuffed in a hot dog an RG designation today.

• Attenuation of Coaxial Transmission Line

Attenuation is the reduction in the strength of a signal. Attenuation of RF cable refers to signal loss. The coaxial cable is used to transfer power between the radio and antenna, in one direction, at any given time. Due to limitations of the cable, some power is lost along the length of the RF cable, known as attenuation.

Attenuation is defined in terms of decibels per unit length, and at a given frequency and 100 ft length is a common reference for comparison since the longer the cable the more attenuation occurs.

Attenuation Charts

Common Cable Attenuation Chart

VHF / UHF / GHz Attenuation Chart

• dB loss per 100 ft

Cable Options to Antenna

RG-58

thin, 50Ω, somewhat lossy

Used for low power signal and RF connections. The cable has a characteristic impedance of either 50Ω or 52Ω. RG-58 CB coaxial is an affordable choice for basic CB installations. RG-58 (CB cable) has a high loss factor in VHF and UHF frequencies, so it really only is useful in runs less than 50 feet for frequencies above 100 MHz, and 20 feet for frequencies above 400 MHz.

Because it is flexible and thin, this cable is often used for vehicle installations. Suitable for vehicle installs for CB radio and HF amateur radio.

In ham radio you typically only see RG-58 being used for short jumper connections, such as 3ft between an SWR/Power meter and a transceiver, or an antenna matching unit.

Commonly used for Citizens Band radio.

RG-8x / Mini-8

thin,

This cable is .242" diameter with a #16 AWG stranded center conductor and a foam dielectric.

RG-8/U

thick, 50Ω, low loss

This cable is suitable for 50-75 foot runs in the VHF/UHF range. The cable is considered by some to be obsolete. The cable has a characteristic impedance of 50Ω. This cable is .405" in diameter with a #13 AWG center conductor and a solid polyethylene dielectric.

RG8x is 50 Ohm cable that is about the same physical size as RG6. It is fairly high loss however and is not that well suited for 70cm except in short runs, however, is suitable for longer runs in the VHF 2m band. RG8 (RG213) is larger 50 Ohm cable that has less loss than RG8X.

RG-213

• thick, 50Ω, lower loss

RG-213 is pretty much the standard in ham radio coaxial cable for HF, and short runs of VHF due to price and general application. It is considered to be a replacement to RG-8 and much better suited for both VHF and UHF operation. The cable has a characteristic impedance of 50Ω. The specifications for RG-213 are tight as compared to RG-8, increasing the consistency from one manufacturer to the next. RG213 is low loss cable with a non-contaminating jacket.

Commonly used for Amateur Radio.

UR-67

LMR-400

thick, 50Ω, very low loss

There are different forms of Times Microwave LMR400. Standard LMR400 has a copper covered solid aluminum center conductor. LMR400/UF has a stranded copper center conductor, designed to replace Belden 9913. Standard LMR 400 Coax will have .7 dB loss at 30 MHz, with a length of 100 Feet.

Commonly used for Amateur Radio for 2m, 70cm, and above frequency

Belden 9913

thick, 50Ω, very low loss

His similar attenuation characteristics to LMR-400. People tend to prefer LMR-400 as a replacement for Belden 9913. Some reasons include that Belden 9913 has a solid center conductor making it less flexible and Belden 9913 is more moisture prone. The 9913 dielectric is somewhat more fragile than the cellular polyethylene LMR400 dielectric, however, Belden 9913F also has a polyethylene foam dielectric.

• .405" diameter with a #10AWG center conductor

Jumper (Patch) Cable

From the transceiver to an antenna matching unit, swr, power meter, or linear amplifier, the use of a short, flexible jumper cable is needed. These tend to have higher attenuation, the tradeoff being flexibility for signal loss. At lengths of 3ft to 6ft the attenuation is negligible.

RG-58

CB and jumper for ham radio. Lossy.

LMR-240, 200 and 195

Because LMR-400 is thick and can put a lot of stress on the connectors of equipment, thinner more flexible alternatives are preferred for jumper use.

LMR-195 is thin and flexible. RFC195 is LMR-195 equivalent and suitable for jumpers on 2m and 70cm application in lengths of 6ft or less. LMR-195 has less attenuation than does RG-58U at all frequencies. At CB frequencies it is 1.8 vs 2.5 and at 70cm ham it is 4.8 vs 7.4. LMR-195 has lower loss than other RG ‘58’ type cables. This is achieved through the use of a high velocity dielectric and a bonded aluminum tape outer conductor.