What are RG108 Coaxial Cables?

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- everything RF

Jan 17, 2023

RG108 Coaxial Cables are a type of cable that has been designed for carrying high frequency electromagnetic signals over long distances, owing to its high degree of signal integrity and lower signal loss.


The RG-108/A/U is a 78-ohm coaxial cable with an overall diameter of 0.235 inches and a voltage rating of up to 1000 Vrms. It consists of two inner tinned copper wires (carrying the electrical signal) with 7 x 28 stranding construction. The inner conductors are enclosed by an insulation layer made of Polyethylene (PE). The insulation layer is then completely enclosed by 1 tinned copper braid shield that forms the outer conductor and also provides shielding against electromagnetic interference (EMI). Finally, the structure is covered with an outermost layer - called a jacket - made of Polyvinyl Chloride (PVC) or XL polyolefin. The jacket protects the cable core from mechanical, moisture, and chemical issues.

The RG108/A/U cable exhibits capacitance of approximately 20 pF/ft (65.78 pF/m), signal attenuation of around 2.8 dB/100 ft at 10 MHz (signal attenuation of the cable depending on the frequency) and has a velocity of propagation of 67%. It has a center conductor measuring 0.0378 inches (0.96 mm) in diameter and an insulation layer measuring 0.0787 inches (2 mm) in diameter.

Key Specifications of RG-108/U Coaxial Cables


Typical Value

Overall Diameter (inch)


Characteristic Impedance (Zo)

78 ohms

Maximum Voltage Rating (RMS)

1000 V

Cable Capacitance (pF/ft)


Attenuation (dB/100 ft, @ 10 MHz)



Polyethylene (PE)

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