Many radio amateurs assume that if they are only running 100W, a high-power BALUN is unnecessary. However, this assumption overlooks a critical factor in antenna systems: voltage surges.

High Voltage Surges in Antennas

Antennas—and the BALUNs connected to them—are frequently exposed to high voltage surges caused by nearby lightning strikes, static buildup, and even rapid weather changes. These transient voltages can be many times higher than the normal RF voltages present during transmission.

Even though a low-power BALUN may be rated for your transmission power, it may not have the insulation strength to survive these surges. This leads to long-term degradation, even if the BALUN does not fail immediately.

The Hidden Danger: Insulation Breakdown

Low-power BALUNs often use windings with standard dielectric insulation, designed only to handle expected RF voltages. However, frequent exposure to static discharges and induced surges causes microscopic burn holes in the insulation over time.

These micro burns:

• Do not cause immediate failure but significantly shorten the lifespan of the BALUN.
• Lead to progressive degradation, eventually resulting in short circuits or arcing faults.
• Increase loss and instability in your antenna system.

In contrast, high-power BALUNs are constructed with superior insulation materials and windings designed to handle much higher voltages. They are built to withstand repeated surges without degrading over time.

Why Choose a High-Power BALUN for Low-Power Operation?

Even if you only operate at 100W, using a kilowatt-rated BALUN provides significant advantages:

• Increased Reliability – Less risk of long-term damage from environmental stress.
• Better Insulation – Handles high voltage surges without breaking down.
• Longer Lifespan – Resists degradation over time, saving you from frequent replacements.
• Future-Proofing – If you ever decide to run higher power, your BALUN is already capable.

Conclusion

Investing in a high-power BALUN isn’t just about handling higher transmission power—it’s about protecting your antenna system from real-world environmental stresses that can degrade or destroy low-power BALUNs over time. Even at 100W, a robust, kilowatt-rated BALUN ensures reliability, longevity, and peace of mind.

For serious amateur operators, it’s a small investment for long-term performance!

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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.