Why Cheap ABS Plastic Is Bad for High Power RF Baluns and Chokes

When designing or building high power RF baluns and chokes, material choice is crucial not only for electrical performance but also for thermal stability, mechanical integrity, and long-term reliability. While ABS (Acrylonitrile Butadiene Styrene) plastic is commonly used due to its affordability and ease of fabrication, it poses significant drawbacks when used in high power RF applications.

1. Poor Thermal Resistance
High power baluns and chokes can dissipate significant amounts of heat, especially when subjected to continuous wave (CW) or digital modes at high duty cycles. ABS plastic typically has a maximum operating temperature of around 85°C. Beyond this, the material begins to soften and deform. In a high RF environment, even moderate heating can cause structural degradation, leading to component failure, misalignment of windings, or even enclosure melting.

2. RF Dielectric Losses
ABS is not a low-loss dielectric. Its dielectric loss tangent is relatively high compared to materials like PTFE, polypropylene, or certain ceramics. This means that when exposed to strong RF fields, ABS can absorb part of the energy, leading to additional heating and inefficiency. This is especially problematic at VHF, UHF, and above, where dielectric losses become more prominent.

3. Outgassing and Carbon Tracking
At elevated temperatures and under high electric fields, ABS can outgas volatile compounds, leading to contamination and potential arcing. Additionally, under prolonged stress, carbon tracking can occur on its surface, forming conductive paths that may short circuit windings or compromise isolation between components.

4. UV Degradation and Mechanical Fatigue
In outdoor installations, ABS degrades quickly under UV exposure, becoming brittle and discolored. Over time, this can lead to cracking, compromised weatherproofing, and reduced mechanical strength. High power RF components are often mounted in enclosures that need to withstand environmental extremes for years; ABS does not meet the durability standards required for such use.

5. Alternatives to ABS
For high power RF applications, especially in baluns and chokes, better alternatives include:

  • PTFE (Teflon): Excellent thermal and RF properties, low dielectric loss.
  • Polycarbonate or PC-ABS blends: Better thermal resistance and toughness, though still inferior to PTFE.
  • Glass-filled Nylon: Good mechanical strength and moderate thermal stability.
  • ASA or UV-stabilized polycarbonate: Better suited for outdoor use.
  • Aluminum or RF-transparent fiberglass enclosures: For mechanical rigidity and EMI shielding.

Conclusion

While cheap ABS plastic may be appealing for prototyping or low-power use, it introduces unacceptable risks in high power RF baluns and chokes. The combination of thermal limitations, RF inefficiencies, and mechanical fragility makes it unsuitable for long-term, high-performance applications. Choosing the right materials ensures not just optimal RF performance, but also safety and durability.

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Written by Joeri Van Dooren, ON6URE – RF, electronics and software engineer, complex platform and antenna designer. Founder of RF.Guru. An expert in active and passive antennas, high-power RF transformers, and custom RF solutions, he has also engineered telecom and broadcast hardware, including set-top boxes, transcoders, and E1/T1 switchboards. His expertise spans high-power RF, embedded systems, digital signal processing, and complex software platforms, driving innovation in both amateur and professional communications industries.