What are RG400 Coaxial Cables?

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- everything RF

Feb 1, 2023

RG400 coaxial cables are designed for high-speed data transmission over medium to long distances. They are often used in the data transmission environment for communications applications such as voice, video, and data.


RG400/U Cable Construction

The RG400/U is a 50-ohm coaxial cable with an overall diameter of 0.195 inches and a voltage rating of up to 1900 Vrms. It has an internal silver-covered copper conductor with a 19-stranding construction (carrying the electrical signal), which is enclosed by an insulation layer made of Polytetrafluoroethylene (PTFE). The insulation layer is then completely enclosed by two silver-covered copper braid shields that form the outer conductor and also provide shielding against electromagnetic interference (EMI). Finally, the structure is covered with an outermost layer - called a jacket - made of Fluorinated ethylene propylene (FEP-IX). The jacket protects the cable core from mechanical, moisture, and chemical issues.

The RG400/U cable exhibits capacitance of approximately 29.4 pF/ft (96.5 pF/m), signal attenuation of around 9.6 dB/100 ft at 400 MHz (signal attenuation of the cable depending on the frequency), and has a velocity of propagation of 69.5%.It has a center 19-stranding conductor design measuring 0.0384 inches (0.975 mm) in diameter and an insulation layer measuring 0.116 inches (2.94 mm) in diameter. This cable is ideal for use in RF applications of military and commercial equipment. It has an operating temperature of -55˚C to + 200˚C.

Key Specifications of RG400//U Coaxial Cables


Typical Value

Overall Diameter (inch)


Characteristic Impedance (Zo)

50 ohms

Maximum Voltage Rating (RMS)

1900 V

Cable Capacitance (pF/ft)


Attenuation (dB/100 ft, @ 400 MHz)



Polytetrafluoroethylene (PTFE)

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