The SWR Myth: The Story of the "Lost" Power That Isn't Really Lost

In amateur radio, few topics are as misunderstood—or as fearfully obsessed over—as Standing Wave Ratio, or SWR. The internet is filled with myths about how "bad SWR" burns your power into thin air or destroys your transmitter. But let’s set the record straight: SWR doesn’t measure antenna efficiency, and power isn't mysteriously disappearing. Let's dive into the physics, the misconceptions, and the truth about where your power really goes.

What SWR Actually Measures

SWR is simply a measure of how well the impedance of your antenna system matches the output impedance of your transmitter (typically 50 ohms). A 1:1 SWR means a perfect match. A 2:1 means a mismatch, with some power reflecting back.

Important: Reflected power is not lost—it’s reflected. Like an echo in a hallway, the energy bounces back and forth until it’s either radiated or absorbed.

Where Does the Reflected Power Go?

Here’s the part many get wrong:

  • Reflected power does not get "lost" in the feedline (unless losses are high).
  • It does not radiate from the braid (unless you have return currents—another issue altogether).
  • It does not evaporate into the ether.

In a typical system without a tuner, some power bounces back from the antenna, reflects off the transmitter output stage, and continues back and forth in the coax. Over time, the power ends up being radiated anyway—unless the feedline is lossy or long. Then yes, some energy is lost as heat due to standing waves. But it’s rarely as dramatic as people think.

Visualizing the Power Flow

Imagine a swimming pool with waves bouncing off the edges. That’s what’s happening inside your coax with a mismatch: forward and reflected waves superimpose, creating standing wave patterns. The energy is still in the system, sloshing around.

Eventually:

  • The transmitter re-absorbs part of the wave.
  • Part of it gets radiated.
  • Some of it is lost as heat in the coax if the cable is long or cheap.

This means your power isn’t just disappearing. It’s still trying to reach the antenna—just not very cleanly.

The Real Losses: Coax and Tuner

So where do we really lose power?

  • Coaxial Feedline Losses:
    • High SWR increases the voltage and current peaks in the coax.
    • This amplifies the coax's internal losses (especially in cheap RG-58 or at high frequencies).
  • Tuner Losses:
    • Tuners don't eliminate SWR at the antenna—they only hide it from the radio.
    • Matching a high SWR can require extreme inductance/capacitance, resulting in several dB of loss in the tuner.
    • Sometimes the tuner adds more loss than the coax would've with the mismatch!

Practical Example

Let’s say you have:

  • 10m of RG-213 coax
  • A 3:1 SWR at the antenna
  • Your tuner brings it down to 1:1 at the shack

Result:

  • The coax sees standing waves with moderate loss—maybe 1.5–2 dB
  • The tuner may add 1–2 dB more loss
  • Net result: 3–4 dB lost

Compare that to a system where you accept the 3:1 mismatch and feed it directly:

  • The coax loss may only be 1.5–2 dB total
  • You skip the tuner and save its losses

Sometimes the imperfect match is the better choice!

Myth: 1:1 SWR Means Efficient Antenna

Nope.

You can have a dummy load with 1:1 SWR—it radiates zero. You can have a very lossy antenna that matches perfectly.

Efficiency is about radiation resistance and losses—not SWR.

Antenna Radiation R Loss R Total R Efficiency SWR
Good design 50Ω 2Ω 52Ω 96% 2:1
Poor radiator 2Ω 20Ω 22Ω 9% 1:1

Chasing 1:1 does nothing if your antenna is a bad radiator.

Reception: Does SWR Matter?

Not really.

Receivers have very high input impedance and sensitivity. The amount of power received is so low that the reflection loss is negligible.

Even with high SWR, your antenna can still receive quite well. What ruins reception more often is common-mode noise—which has nothing to do with SWR.

Key Takeaways

  • SWR ≠ Efficiency: It’s just a match indicator.
  • Power isn’t lost: It bounces around. Loss only happens through heat (cable/tuner).
  • Tuner ≠ Free lunch: Matching high SWR costs you efficiency.
  • Reception isn't affected: SWR doesn't kill receive performance.
  • Better design = Less worry: Focus on good antennas, not perfect matches.

Final Word

SWR is a useful tool—but it’s not a performance meter. A bit of mismatch won’t ruin your signal, and sometimes, avoiding the tuner yields better results. Know where your real losses are—and stop chasing ghosts in the standing waves.

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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.