Understanding Standing Wave Ratio (SWR)

Why is SWR Important?

The Standing Wave Ratio (SWR) shows how efficiently transmitter power reaches the antenna. An SWR of 1:1 represents a perfect match; higher values mean greater reflected power and losses.

Monitor your system with the SWR Calculator to predict behavior under different conditions.

Common Causes of High SWR

• Feedline length or characteristic impedance mismatched with the antenna
• Moisture or corrosion in connectors
• Reactive loads introduced by traps, baluns, or loading coils
• Operation outside the antenna’s designed frequency band

Managing Reflected Power

Most modern transmitters fold back their output power when SWR exceeds 2:1 to protect the final amplifier stage. Sustained high SWR can overheat feedlines and impedance matching networks.

Improvement Techniques

1. Re-measure the physical dimensions of the antenna and correct any asymmetry.
2. Place the antenna tuner at the feed point instead of the shack to minimize coax losses.
3. Install a common-mode choke to keep RF off the outer shield of the coax.
4. Evaluate Coax Loss to confirm the cable isn’t introducing excessive attenuation.

Field Diagnostics

Carry a portable antenna analyzer or a VNA. Sweep the bands you use and record the SWR minimums. Compare the curves before and after adjustments to confirm improvements.