Tuning: Analyzer & SWR

What SWR measures

SWR (standing wave ratio) tells you how well your antenna system’s impedance matches your radio, usually 50 ohms. 1:1 is a perfect match. Below 1.5:1 is excellent, and under 2:1 is fine for most radios. Above that, many radios reduce power to protect themselves.

What SWR does not tell you is how well your antenna radiates. A dummy load has a perfect SWR and puts out nothing. A good match is necessary, but it isn’t the same as a good antenna.

Tuning with an analyzer

• Connect the analyzer (a RigExpert, NanoVNA or similar) where the coax meets the radio, or right at the antenna for the most accurate picture.
• Sweep across the band and find where the SWR is lowest. That’s where the antenna is resonant.
• If the dip is below the band, the antenna is too long: shorten it. If it’s above, it’s too short: lengthen it.
• Make small changes, a few centimetres at a time, and measure again. Change both legs of a dipole equally.

Antenna tuners

A tuner (ATU) matches a mismatched antenna to your radio so it can deliver full power. It’s essential for multi-band wires like doublets. But a tuner at the radio doesn’t fix losses in the coax or make a poor antenna better. It just makes the radio happy. A tuner at the antenna feedpoint is more efficient than one in the shack.

When readings don’t make sense

• SWR changes when you touch the coax? Current is flowing on the outside of the shield. Add a common-mode choke at the feedpoint.
• Readings drift with weather? Check for water in connectors.
• Perfect SWR everywhere? Suspect a lossy cable or a bad connection acting like a dummy load.

Last updated October 2026.