What are RG178 Coaxial Cables?

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- everything RF

Jan 20, 2023

RG178 Coaxial Cables are a type of cable commonly used for high frequency signal transmission. They exhibit high degree of signal integrity and low signal attenuation, making them suitable long haul communication links.


RG178/A/B/U Cable Construction

The RG178/A/B/U is a 50-ohm coaxial cable with an overall diameter of 0.075 inches and a voltage rating of up to 1000 Vrms. It has an inner silver plated copper wire (SCW) or silver-covered copper-clad steel (SCCS) wire (carrying the electrical signal) with 7 x 38 stranding construction. The inner conductor is enclosed by an insulation layer made of Polytetrafluoroethylene (PTFE). The insulation layer is then completely enclosed by 1 silver-covered copper (SC) 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 fluorinated ethylene propylene (FEP-IX).  The jacket protects the cable core from mechanical, moisture, and chemical issues.

The RG178/A/B/U cable exhibits capacitance of approximately 29 pF/ft (95.39 pF/m), and signal attenuation of around 29.0 dB/100 ft at 400 MHz (signal attenuation of the cable depending on the frequency) and has a velocity of propagation of 69 %. It has a center conductor measuring 0.0120 inches (0.3048 mm) in diameter and an insulation layer measuring 0.034 inches (0.8636 mm) in diameter. This cable is ideal for use in RF, PCB, and panel interconnect applications.

Key Specifications of RG-178/A/B/U Coaxial Cables


Typical Value

Overall Diameter (inch)


Characteristic Impedance (Zo)

50 ohms

Maximum Voltage Rating (RMS)

1000 V

Cable Capacitance (pF/ft)


Attenuation (dB/100 ft, @ 400 MHz)



Polytetrafluoroethylene (PTFE)

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