RG402 Coaxial Cable Low-Loss Selection and Installation Guide

In radio frequency (RF) and microwave systems, cables are not merely "transmission lines," but core components that determine signal integrity and system stability. RG402 coaxial cables, due to their excellent high-frequency performance and structural stability, are widely used in communications, test instruments, military electronics, and industrial control. This article will provide a systematic analysis of aspects such as structural principles, technical parameters, application scenarios, selection recommendations, and common problems to help engineers and purchasing personnel gain a comprehensive understanding.

I. What is an RG402 coaxial cable?

RG402 is a semi-rigid radio frequency coaxial cable characterized by:

• 50Ω Characteristic Impedance
• Silver-plated copper conductor
• PTFE (polytetrafluoroethylene) dielectric
• Seamless copper outer conductor
• Supports high-frequency signal transmission (up to 18GHz or even higher)

It conforms to the U.S. military standard MIL-C-17 and is widely used in military and aerospace systems.

II. Structural Analysis of RG402

III. Key Technical Parameters of RG402

• Capacitance: 95.1pF/m
• Impedance: 50Ω (±2Ω)
• 1GHz Attenuation: 11.1dB/100ft (approx. 36.4dB/100m)
• Rated Voltage: 5.0KVrms
• Maximum Power (1GHz): 450W
• Outer diameter: 0.141 inch (approximately 3.58 mm)
• Frequency range: DC – 18GHz
• Voltage Standing Wave Ratio (VSWR): ≤ 1.3
• Operating temperature: -55℃ to +200℃
• Shielding effectiveness: >100 dB

IV. Performance Advantages of RG402

The RG402 is a semi-rigid coaxial cable designed specifically for high-frequency applications, making it a top choice for professional equipment due to its four core advantages. It utilizes a silver-plated conductor with PTFE dielectric, resulting in exceptionally low signal loss in the microwave band, meeting the demands of high-precision transmission. The copper outer conductor structure effectively isolates electromagnetic interference (EMI/RFI), preventing signal distortion. Even in harsh environments with drastic temperature variations, its performance remains stable and unaffected by environmental fluctuations. Furthermore, it can be bent and fixed in shape, offering flexible cabling options and making it particularly suitable for confined spaces such as server racks. Because of these practical characteristics, the RG402 is widely used in microwave communication systems, RF test equipment, satellite communication systems, radar systems, and high-precision laboratory instruments, perfectly matching the high signal transmission requirements of professional applications.

V. Standard Installation Steps for RG402 Coaxial Cable

Stripping: Use specialized tools to strip the wires to the specified dimensions, avoiding damage to the inner conductor and insulation.

Soldering: Use solder with a melting point >125℃ for the inner conductor and>150℃ for the outer conductor to prevent cold solder joints.

Fixing: Bending radius ≥12.5mm to avoid pulling or twisting the cable;

Testing: After installation, test VSWR (≤1.3 is preferred) and insulation resistance.

VI. Case Study of RG402 Coaxial Cable Application

A vehicle radar manufacturer specializing in the R&D and manufacturing of 77GHz FMCW millimeter-wave radar has long faced performance bottlenecks in its production line testing. The ordinary RF cables they originally used had two major problems: first, severe signal attenuation, with an attenuation of up to 2.1dB per meter, directly resulting in a radar ranging error of up to 15cm, severely restricting the product's accuracy; second, insufficient stability, with noticeable signal drift appearing after only three plug-and-play cycles, requiring frequent shutdowns for recalibration, each calibration taking up to 42 minutes, significantly dragging down the overall production line efficiency.

After replacing with RG402 cable:

• The attenuation was reduced to 0.7dB/meter, and the ranging error was reduced to within 5cm.
• After 500 insertions and removals, the VSWR fluctuation was ≤±0.1dB, meeting the requirements for repeated testing on the production line.
• The calibration time was reduced from 42 minutes to 28 minutes, and the production efficiency was improved by 33%.

Remember these three key parameters: 50Ω impedance, 34GHz upper limit, and 12.5mm minimum bending radius. These will meet the needs of most high-frequency transmission scenarios.

VII. Installation and Usage Precautions

• Do not bend repeatedly (this will cause micro-cracks).
• Bending radius is typically ≥ 5 times the outer diameter.
• Welding temperature control.
• Avoid external pulling forces.

Maintenance tips: Regularly check the contact of the joints. In humid environments, moisture-proof sealing is required to prevent moisture from seeping in.

VIII. RG402 Frequently Asked Questions (FAQ)

Q1: Can RG402 be used for 5G communication?

Yes. RG402 is perfectly suitable as long as the frequency range is within the cable's rated frequency (e.g., Sub-6GHz).

Q2: What is the difference between RG402 and ordinary braided coaxial cable?

RG402 has a semi-rigid structure, offering higher shielding performance and lower loss, but it is less flexible than braided structures.

Q3: How long can the RG402 be?

Theoretically, it can be quite long, but for high-frequency applications, short-distance use (<1 meter) is generally recommended to control losses.

Q4: Can it be used outdoors?

Yes, but it is recommended to add a protective case or use waterproof components.

Q5: Does the RG402 meet military standards?

It meets MIL-C-17 specifications.