Comparisons

RG142 & RG400: High Performance RF Coax Comparison

01/07/2026

RG142 and RG400 are commonly compared high performance RF coaxial cables used in demanding signal transmission systems. Although they share similar constructions including silver plated copper conductors, PTFE dielectric, and braided shielding their electrical behavior, mechanical flexibility, and handling characteristics differ in ways that can impact system performance and installation. Understanding these differences helps engineers and procurement teams make more informed cable selection decisions in RF and microwave applications.

Table Of Contents

Structural comparison of RG142 and RG400 cables
RG142 vs RG400 Key Electrical Specifications Comparison
Mechanical and Physical Performance Comparison
When to Choose RG142 vs RG400
FAQ
Conclusion

Structural comparison of RG142 and RG400 cables

Center Conductor Structure and Material

Both RG142 and RG400 use a solid silver plated copper center conductor, but the conductor diameter differs, which directly affects current distribution and RF loss.

RG142 uses a smaller diameter conductor (approx. 0.036 in / 0.91 mm), while RG400 uses a thicker conductor (approx. 0.040 in / 1.02 mm). The larger conductor in RG400 reduces conductor resistance at high frequencies, contributing to slightly lower attenuation and improved power handling.

Dielectric Material and Geometry (PTFE)

Both cables utilize a solid PTFE dielectric, selected for its low dielectric loss, stable dielectric constant (approximately 2.1), and wide operating temperature range. While the dielectric material is the same, the dielectric geometry differs. RG142 typically features a dielectric diameter of approximately 0.116 in (2.95 mm), whereas RG400 employs a larger dielectric diameter of approximately 0.164 in (4.17 mm). This dimensional difference affects impedance geometry and signal propagation, resulting in a velocity of propagation of approximately 69% for RG142 and approximately 70% for RG400.

Shielding Construction and Coverage

Shielding design represents a key structural distinction between the two cables. RG142 incorporates a single silver plated copper braided shield, while RG400 is constructed with a dual silver plated copper braided shield.The dual braid configuration of RG400 provides enhanced shielding effectiveness, resulting in improved electromagnetic interference (EMI) suppression and greater signal stability in electrically noisy RF environments.

Outer Jacket Material and Mechanical Dimensions

Both RG142 and RG400 are jacketed with FEP (fluorinated ethylene propylene), a material known for its chemical resistance, flame retardancy, and suitability for wide temperature ranges, typically from −65°C to +200°C. Despite using the same jacket material, the overall cable diameters differ significantly. RG142 has an outer diameter of approximately 0.195 in (4.95 mm), while RG400 measures approximately 0.275 in (6.99 mm). These dimensional differences influence mechanical handling characteristics, with RG142 offering greater flexibility and RG400 providing increased mechanical robustness.

RG142 vs RG400 Key Electrical Specifications Comparison

Parameter	RG142	RG400
Nominal Impedance	50 Ω	50 Ω
Maximum Operating Frequency	Up to ~18 GHz	Up to ~18 GHz
Typical Attenuation	~15.3 dB / 100 ft	~13.5 dB / 100 ft
Typical Attenuation	~52 dB / 100 ft	~45 dB / 100 ft
Velocity of Propagation	~69%	~70%
Capacitance	~29.5 pF / ft	~26.8 pF / ft
Shielding Construction	Single silver-plated copper braid	Dual silver-plated copper braid
Maximum Power Rating	~190 W	~200 W
Operating Temperature Range	−65°C to +200°C	−65°C to +200°C

Mechanical and Physical Performance Comparison

Mechanical and Physical Specifications Comparison Table

Parameter	RG142	RG400
Nominal Outer Diameter	~0.195 in (4.95 mm)	~0.275 in (6.99 mm)
Approximate Weight	~0.040 lb/ft (0.060 kg/m)	~0.083 lb/ft (0.124 kg/m)
Minimum Bend Radius	~1.0 in (25 mm)	~2.0 in (51 mm)
Relative Flexibility	Higher (smaller diameter)	Lower (larger diameter)
Outer Jacket Material	FEP	FEP
Operating Temperature Range	−65°C to +200°C	−65°C to +200°C
Chemical & Flame Resistance	Excellent	Excellent

Cable Diameter, Weight, and Routing Considerations

RG142 features a smaller outer diameter and lower weight per unit length, making it easier to route in confined spaces or densely packed equipment. In contrast, RG400’s larger diameter and higher mass result in increased mechanical stiffness, which can limit routing flexibility but provides greater physical robustness in fixed installations.

When to Choose RG142 vs RG400

Applications with Limited Space and High Flexibility Requirements

RG142 is generally the preferred option when routing space is limited or frequent bending is required. Its smaller outer diameter, lower weight, and tighter minimum bend radius make it easier to install in densely packed enclosures or equipment with complex internal routing. In such cases, RG142 can meet high frequency requirements while simplifying installation and reducing mechanical stress during assembly.

Systems Sensitive to High Frequency Loss and Signal Stability

RG400 is better suited for systems where attenuation control and signal stability at higher frequencies are critical. RG400 exhibits lower attenuation and enhanced shielding performance compared to RG142, particularly as frequency increases. These characteristics make RG400 a more appropriate choice for RF and microwave systems where maintaining consistent signal quality is a primary design objective.

Projects Requiring Long Term Reliability and Mechanical Robustness

For projects where long term reliability and mechanical robustness are prioritized, RG400 is often selected due to its thicker construction and dual braided shielding. Although both RG142 and RG400 use the same FEP jacket material and share similar temperature and chemical resistance ratings, RG400’s more robust structure provides additional margin against mechanical stress and electromagnetic interference over extended service life.

FAQ

Q1: What is the main difference between RG142 and RG400 coaxial cables?

The primary difference between RG142 and RG400 lies in their physical size and resulting electrical and mechanical characteristics. RG400 has a larger outer diameter and conductor size, which leads to lower attenuation and higher power handling compared to RG142. In contrast, RG142 offers a smaller diameter and tighter bend radius, making it easier to route in space-constrained installations.

Q2: Do RG142 and RG400 have the same impedance and frequency rating?

Yes. Both RG142 and RG400 are standardized 50-ohm coaxial cables and are typically rated for operation up to approximately 18 GHz. Their shared impedance and frequency range make them interchangeable from a system-matching perspective, although their loss and mechanical behavior differ.

Q3: Why does RG400 usually have lower attenuation than RG142?

RG400’s lower attenuation is primarily a result of its larger conductor diameter and overall cable geometry. A larger conductor reduces resistive losses at high frequencies, while the increased dielectric dimensions improve signal propagation efficiency. These design factors collectively reduce insertion loss compared to smaller-diameter cables such as RG142.

Q4: Is RG142 better than RG400 for tight or complex cable routing?

In installations where routing space is limited or frequent bending is required, RG142 is often preferred. Its smaller outer diameter and tighter minimum bend radius allow for easier installation in dense assemblies. However, this advantage comes with higher attenuation compared to RG400, which must be considered at higher frequencies or longer cable lengths.

Q5: Which cable is more suitable for long term reliability in harsh environments, RG142 or RG400?

Both RG142 and RG400 use PTFE dielectrics and FEP outer jackets, offering excellent thermal and chemical resistance. However, RG400’s thicker construction provides greater mechanical robustness, making it more suitable for installations where long-term durability and resistance to mechanical stress are critical.

Conclusion

RG142 and RG400 share similar materials and baseline specifications, but their differences in conductor size, shielding structure, and mechanical dimensions lead to distinct performance and installation characteristics. RG142 offers advantages in flexibility and space constrained routing, while RG400 provides lower attenuation, stronger shielding, and greater performance margin at higher frequencies. Selecting between the two should be based on system level requirements balancing electrical performance, mechanical constraints, and long term reliability rather than relying on a single specification.

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