To Resonate or Not to Resonate – That’s the Ongoing Question…

At RF.Guru, we get this question more often than any other:

“Does my antenna need to be resonant?”

The answer is simple, yet often misunderstood. Time to finally clear things up.

What does resonance really mean?

Resonance, in the context of antennas, is a purely electrical phenomenon. It simply means that the reactive components – the inductive and capacitive parts – cancel each other out at a particular frequency. The result? The antenna presents a purely resistive impedance at that frequency, typically close to 50 ohms. This allows your transmitter to transfer maximum power without significant losses in the feedline.

But here’s the thing: a resonant antenna is not necessarily a well-performing antenna.

Resonance says nothing about radiating performance

An antenna can be perfectly resonant and still perform poorly. For example:

  • It may hang low to the ground, causing radiation losses.
  • It may have an unfavourable radiation pattern (such as radiating mostly upwards instead of along the horizon).
  • It may be surrounded by obstacles or suffer from ground losses.

Conversely, a non-resonant antenna, with proper matching and strategic placement, can perform extremely well.

Myth: Low SWR = Good Antenna

This is perhaps the biggest misconception. A low SWR only means your transmitter can deliver its power without reflection. It says nothing about how – or where – that power is actually radiated.

For instance, a dummy load has a perfect SWR of 1:1… but radiates absolutely nothing. It’s a resistor, not an antenna.

Focus on What Really Matters

Instead of blindly chasing resonance, the focus should be on:

  • The placement and height of the antenna
  • Proper matching to the transmitter (via a tuner or matching network)
  • Radiation efficiency and pattern
  • Losses in the feedline and surrounding environment

Real-World Example

A 29-metre wire fed through a 4:1 UNUN is rarely resonant on the amateur bands. Yet this antenna, when correctly installed and paired with a good choke, can perform surprisingly well across multiple HF bands. Why? Because its radiation properties are favourable, and the losses in the system remain under control.

Conclusion

Resonance is a tool – not a goal in itself.

Think of it as one part of a larger system. It’s convenient if you want to connect an antenna directly to a transmitter without a tuner. But in practice, the best antennas are often those that are well-positioned, intelligently designed, and properly matched – even if they’re not resonant.

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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.