Why Thick Aluminum Tubes Make Better Antennas Than Thin Wire

When it comes to designing efficient radiating elements for antennas, the geometry and physical dimensions of the conductor play a vital role. While it's tempting to think of an antenna as "just a wire," the choice between a thick tube and a thin wire can significantly impact performance. Here's why a 35mm diameter aluminum tube is superior to a 2mm wire in most real-world antenna applications.

Reduced Ohmic Losses

Ohmic (resistive) losses in an antenna are directly tied to the surface area and resistance of the conductor. At RF frequencies, current flows primarily along the surface of the conductor due to the skin effect. A thicker conductor, like a 35mm tube, offers vastly more surface area than a 2mm wire, drastically reducing resistance and therefore loss. Less heat, more radiation.

Lower Losses from Corona and Voltage Breakdown

Thicker tubes can handle higher voltage gradients before arcing or corona discharge begins. This is especially important for high-power or high-voltage feedpoints. A 2mm wire will reach dielectric breakdown limits at much lower voltages, especially in humid or dirty environments.

Improved Bandwidth

One of the most significant advantages of using a thicker radiator is increased bandwidth. The radiation resistance varies less with frequency for fat conductors, and the reactance slope is shallower. This means the antenna remains better matched over a broader frequency range. For multiband or broadband antennas, this is a key performance factor.

Less Detuning by Environmental Factors

A thick aluminum tube is less sensitive to capacitive or inductive coupling with nearby objects like trees, gutters, and fences. A thin wire, especially in close proximity to vegetation or structures, will detune more easily due to its higher impedance sensitivity.

Mechanical Stability and Durability

Beyond RF performance, mechanical integrity matters. A 35mm aluminum tube is significantly more resistant to wind, ice loading, and mechanical fatigue. It keeps its shape, ensuring predictable RF behavior over time. A 2mm wire can stretch, bend, or even break, especially under wind stress.

Better Current Distribution

Thicker conductors promote a more uniform current distribution along the length of the antenna, which can increase efficiency and alter radiation patterns favorably. In contrast, thin conductors have steeper current tapering and higher resistive gradients.

Reduced Proximity Effects and Mutual Coupling

In antenna arrays or setups with nearby metal structures, the thicker radiator is less prone to detuning caused by mutual coupling and proximity effects. It behaves more like an ideal conductor.

Conclusion

Using a 35mm aluminum tube instead of a 2mm wire is not just a mechanical upgrade—it's a performance one. From lower ohmic loss and broader bandwidth to increased robustness and efficiency, a thick radiator brings real advantages. While wires are cheap and easy to install, they compromise many key aspects of antenna behavior. For serious applications, especially in demanding environments or multiband scenarios, go with the tube.

Sometimes, size really does matter.

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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.