Good Enough Isn’t Good Enough Anymore

Why the “Ugly Balun” is too touchy for modern ham radio — and why engineering demands margin

For years, amateur radio lived comfortably with a simple idea: if the SWR looks fine and the station “seems to work,” it’s probably good enough. That mindset survived in an analog world of forgiving receivers, simple audio gear, and operating styles where problems were obvious and slow.

That world is gone.

Today’s typical station is surrounded by switching power supplies, Ethernet, computers, LED lighting, touch controls, cheap chargers, smart devices, and dense neighborhood electronics. Digital systems don’t degrade gracefully. They fail like a cliff. If your RF control is marginal, you don’t get “a little bit of interference” — you get random dropouts, USB glitches, audio distortion, device resets, or a neighbor’s equipment behaving badly.

That is why “good enough” common-mode control is no longer good enough — especially when we talk about the classic coax-coil ugly balun.

The uncomfortable truth about the ugly balun

The “ugly balun” is usually not a balun in the transformer sense. It is a coil of coax intended to act as a common-mode choke, attempting to block RF current flowing on the outside of the coax shield — the current that turns your feedline into an accidental radiator.

The problem is not that it never works. The problem is that it works in a way that is inherently touchy.

• A coiled-coax choke is a reactive choke.
• A real coil of coax is not just an inductor — it has significant inter-turn capacitance.
• This forms a parallel resonant circuit with a narrow impedance peak near resonance.

That means high impedance only over a limited frequency range, and unpredictable behavior outside it. Small changes in coax type, winding spacing, diameter, or even nearby objects can shift the resonance by several MHz.

That is the definition of picky.

Why “picky” is unacceptable for most operators

A touchy component is fine when it is treated like one: measured, tuned, and kept mechanically stable — like a trap or matching network.

But most hams do not want lab instruments hanging in trees.

They want antennas that:

• behave the same in real weather,
• behave the same when the coax is routed slightly differently,
• do not become a different antenna every time something nearby changes,
• do not drag common-mode RF back into the shack.

A resonant coil of coax used as a choke fights all of those goals. Reactive chokes can even resonate with the rest of the system in ways that increase common-mode current rather than reduce it.

That is not a theoretical edge case. It is a reliability problem.

Where an ugly balun is acceptable — and where it is not

Acceptable use cases

• Single-band operation in the higher HF bands like the 10M band and VHF/UHF, where the choke is intentionally tuned.
• Portable, temporary, or experimental setups.
• “Get on the air today” antennas where consequences are low.

Not acceptable as a default

• Stable multiband HF systems
• Lower HF bands
• Predictable EMC behavior
• Repeatable builds with repeatable results

Common-mode control is antenna control

Common-mode current is not just an interference nuisance. It changes the antenna itself.

If common-mode current is significant, the feedline becomes part of the radiating structure, altering:

• radiation pattern,
• feedpoint impedance,
• resonance and tuning,
• SWR behavior,
• received noise.

If common-mode suppression is marginal, then pattern control is marginal. You are operating a moving target.

Why “500 Ω is enough” is a comforting myth

Older advice often focuses on minimum choking impedance numbers: 500 Ω, maybe 1 kΩ. Those numbers come from simplified models and bench thinking, not real EMC environments.

In practice, the difference between 1 kΩ and several kΩ of choking impedance is not cosmetic. It is the difference between marginal attenuation and dominant control.

Modern digital environments demand margin — not barely-there fixes that work until something changes.

The fatal flaw: the ugly balun is mostly reactive

The most dangerous mistake is not using an ugly balun.

The most dangerous mistake is believing it behaves like a broadband, predictable blocker.

Reactive choking can interact with the rest of the system in unpredictable ways. A properly designed ferrite choke, on the other hand, can provide broadband, largely resistive impedance that the system cannot easily “undo.”

Engineering is not “good enough” — it is repeatable

That is the real boundary.

• “Good enough” is a hobby result.
• Engineering is a repeatable result.

If you want a stable antenna system in a modern RF environment:

• Treat common-mode control as part of the antenna design.
• Design for margin, not minimums.
• Avoid touchy, resonant fixes as defaults.
• Remember: common-mode changes your pattern.

That is not elitism. It is simply respecting what modern RF reality demands.

Engineering is not about “good enough.”
It is about designing so the result stays correct when reality moves.

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