What are RG391 Coaxial Cables?

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- everything RF

Jan 31, 2023

RG391 Coaxial Cables are a type of cable that offers excellent signal integrity and low signal loss, making them suitable for long-haul communication links and maritime applications. A high degree of durability and flexible design makes them ideal for both indoor and outdoor scenarios.


The RG391/U is a 72-ohm coaxial cable with an overall diameter of 0.405 inches and a voltage rating of up to 5000 Vrms. It has an internal tinned copper conductor with a 7-stranding construction (carrying the electrical signal), which is enclosed by an insulation layer made of Chlorinated polyethylene (CPE) & 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). The jacket protects the cable core from mechanical, moisture, and chemical issues.

The RG391/U cable exhibits a capacitance of approximately 23.0 pF/ft (75.5 pF/m) and signals attenuation of around 15.0 dB/100 ft at 400 MHz (signal attenuation of the cable depending on the frequency). It has a center 7-stranding conductor design measuring 0.0477 inches (1.21 mm) in diameter and an insulation layer measuring 0.048 inches (1.219 mm) in diameter. This cable is ideal for use in RF applications on Naval shipboard. It has an operating temperature of -55˚C to + 80˚C.

Key Specifications of RG391//U Coaxial Cables


Typical Value

Overall Diameter (inch)


Characteristic Impedance (Zo)

72 ohms

Maximum Voltage Rating (RMS)

5000 V

Cable Capacitance (pF/ft)


Attenuation (dB/100 ft, @ 400 MHz)



Chlorinated polyethylene (CPE) & Polyethylene (PE)

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