Full-Wave Loop Antenna

The full-wave loop is a closed wire loop whose circumference is one wavelength, mounted in a vertical plane and fed at the bottom.

Configuration

The loop stands in a vertical plane and is fed at the bottom; the length field is labelled Circumference. The default is 1.0 m, which is only sensible for very high frequencies; set 0 to get a full-wave circumference for the operating frequency, or enter it explicitly.

Characteristics

• Typical gain around 1.5 dBi with a high takeoff angle around 55 degrees: primarily a short and medium range antenna.
• Broadside pattern (perpendicular to the loop plane), controlled by the azimuth setting, but lobes are broad.
• Distinctly narrowband: the SWR is excellent at resonance and degrades quickly off frequency. Retune (adjust circumference) when changing frequency by more than a fraction of a percent.
• Quiet and clean pattern; a classic choice for regional nets.

Sizing

A full-wave circumference in meters is approximately 300 divided by the frequency in MHz (see Antenna Calculations). Example: about 84 m at 3.6 MHz, about 42 m at 7.1 MHz.

When to use

For reliable short and medium range ionospheric coverage on a fixed frequency. Poor choice for frequency-agile operation because of the narrow match.