Polarization of the Antenna Explained

At its core, antenna polarization refers to the physical orientation of the radio wave’s electric field as it travels through space.

When an alternating current is applied to an antenna, it generates an electromagnetic wave consisting of two components: an electric field (E-field) and a magnetic field (H-field). These two fields always travel perpendicular to each other and perpendicular to the direction of propagation. The orientation of that E-field dictates the antenna’s polarization.

Here is a breakdown of how it works in practice and why it matters for your setups.

1. Linear Polarization

Most standard antennas are linearly polarized, meaning the electric field stays in a single plane. The polarization is determined by how the elements are mounted relative to the earth.

• Horizontal Polarization: If you string up a wire dipole parallel to the ground (like a standard 80m or 160m dipole), the electric field oscillates horizontally. This is the standard for most HF DXing and terrestrial weak-signal VHF/UHF work. It tends to pick up less man-made electrical noise, which is heavily vertically polarized.
• Vertical Polarization: If the antenna element stands straight up, the electric field oscillates vertically. This is standard for local repeater work, mobile setups, and AM broadcast stations. It provides an excellent omnidirectional ground wave.

2. Circular Polarization (CP)

Instead of staying in a single flat plane, the electric and magnetic fields rotate continuously in a corkscrew pattern as they travel.

• Right-Hand Circular Polarization (RHCP) & Left-Hand Circular Polarization (LHCP): Depending on the phase relationship of the driven elements, the wave spins clockwise or counter-clockwise.
• Why it’s used: Circular polarization is vital for LEO (Low Earth Orbit) satellite operations. Because a satellite is tumbling through space, its antenna orientation is constantly changing relative to your position on the ground. If you try to track a tumbling satellite with a linearly polarized antenna (like a standard handheld Moxon or Yagi), you will experience severe, rhythmic signal fading (spin fading). A circularly polarized antenna (like a crossed-Yagi) ensures you maintain a consistent link regardless of the satellite’s physical orientation.

3. The Consequences: Cross-Polarization Loss

For line-of-sight communications, the transmitting and receiving antennas must have matching polarization.

If you try to receive a vertically polarized signal with a horizontally polarized antenna (or vice versa), the theoretical signal loss is infinite. In the real world, due to scattering and reflections, this cross-polarization loss is typically around 20 to 30 dB. That is enough to make a perfectly readable signal completely disappear into the noise floor.

The Skywave Exception: When you are working HF and bouncing signals off the ionosphere, polarization matters much less on the receiving end. The ionosphere heavily refracts and scatters the wave (a phenomenon called Faraday rotation), effectively scrambling the polarization. A signal transmitted horizontally might arrive elliptically or vertically polarized. This is why you can successfully work a DX station using a vertical antenna even if they are transmitting on a horizontal dipole.