What are RG218 Coaxial Cables?

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- everything RF

Jan 23, 2023

RG218 Coaxial Cables are a type of cable that that has been designed for high frequency signal transmission. They exhibit high signal integrity and low signal attenuation making them ideal for long-range communication, telecommunication, and networking applications.


RG218/U Cable Construction

The RG218/U is a 50-ohm coaxial cable with an overall diameter of 0.870 inches and a voltage rating of up to 11000 Vrms. It has an internal bare copper conductor (carrying the electrical signal), which is enclosed by an insulation layer made of Polyethylene (PE). The insulation layer is then completely enclosed by 1 Bare Copper Braid Shields that form 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). The jacket protects the cable core from mechanical, moisture, and chemical issues.

The RG218/U cable exhibits capacitance of approximately 30.8 pF/ft (101.3 pF/m), signal attenuation of around 2.5 dB/100 ft at 400 MHz (signal attenuation of the cable depending on the frequency), and has a velocity of propagation of 66%. It has a center conductor measuring 0.195 inches (4.95 mm) in diameter and an insulation layer measuring 0.680 inches (17.27 mm) in diameter. This cable is ideal for data transmission, RF communication, broadcast, and computer. It has an operating temperature of -40˚C to + 80˚C.

Key Specifications of RG218/U Coaxial Cables


Typical Value

Overall Diameter (inch)


Characteristic Impedance (Zo)

50 ohms

Maximum Voltage Rating (RMS)

11000 V

Cable Capacitance (pF/ft)


Nominal inductance (nH/ft)


Attenuation (dB/100 ft, @ 400 MHz)



Polyethylene (PE)

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