Vertical vs Horizontal Polarization: What Hams Should Know

Every antenna launches its radio waves with a particular polarization, and every receiving antenna prefers one too. For many hams this is a quiet detail that never gets thought about until a mobile station hears a repeater loudly while a friend with a horizontal beam hears nothing, or until someone claims that a vertical is hopeless for DX. The truth is more interesting. Vertical vs horizontal polarization matters a lot in some situations and hardly at all in others, and knowing which is which saves a lot of money and a lot of arguments.

This guide explains what polarization is, how it behaves on the ground wave, on HF skywave paths and on VHF and UHF links, what happens when polarizations do not match and how to choose an antenna with this in mind. It relies on published antenna and propagation references, which are linked in the text.

What Polarization Means

Polarization describes the direction in which the electric field of a radio wave oscillates. The encyclopedia article on antennas explains that the orientation and physical structure of an antenna determine the polarization of the wave it transmits. A linear conductor such as a dipole or a whip, held vertically, produces vertical polarization. Turn the same antenna on its side and the polarization becomes horizontal. In the general case, polarization is elliptical, with linear and circular polarization as the two special cases. In circular polarization the electric field rotates around the direction of travel.

A receiving antenna works best when it matches the polarization of the wave. If it does not, signal strength is lost, and the loss grows as the angle between the two polarizations increases. The same article adds that a circularly polarized antenna can receive vertical and horizontal linear waves equally well, at a cost of 3 dB, but that it is blind to a circular signal of the opposite sense.

One caution: a dipole is only perfectly horizontally polarized when you look at it broadside. The W8JI antenna website points out that moving around toward the ends of a horizontal dipole, the polarization tilts more and more toward vertical. In other words, the labels vertical and horizontal are convenient simplifications, and real antennas radiate a tilted field that depends on direction.

The Ground Wave Likes Vertical

At medium frequencies and the lowest HF bands, a signal can travel along the surface of the Earth as a ground wave. The ground wave article states plainly that only vertically polarized waves travel well in this mode, while horizontally polarized signals are heavily attenuated. Frequencies below 3 MHz travel efficiently as ground waves. Between 3 and 30 MHz the range becomes more modest, and above 30 MHz the ground wave is unimportant. Sea water, with its high conductivity, gives the best propagation, while dry ground and ice perform worst.

That is why broadcasting stations on medium wave use vertical towers, and why a vertical antenna on 160 and 80 metres is a natural choice for local and regional contacts, including nets on a calm evening. If you want your signal to hug the ground for the first hundred kilometres, vertical polarization wins.

What the Ground Does to Each Polarization

Ground reflection is the other half of the story, and it explains most of the practical differences between a horizontal and a vertical antenna. According to the antenna article, between 3 and 30 MHz a large part of the energy from a horizontally polarized antenna reflects off the ground, with almost total reflection at grazing angles. That reflected wave has its phase reversed and can cancel or reinforce the direct wave, depending on the antenna height in wavelengths and the elevation angle. This is the reason a horizontal dipole’s pattern changes with height, as we discuss in our article on antenna height and takeoff angle.

Vertically polarized radiation behaves differently. It is not well reflected by the ground except at grazing incidence or over very highly conducting surfaces such as sea water. At the grazing angles that matter for ground wave propagation, the reflection is in phase with the direct wave and can provide a boost of up to 6 dB. The dipole article adds that the vertical polarization of a monopole is advantageous at low elevation angles, where the ground reflection combines with the direct wave approximately in phase. That is the physical reason verticals are known for low-angle radiation, and why a vertical with a poor ground system loses so much, as our guide on vertical antenna radials explains.

HF Skywave: The Ionosphere Scrambles Polarization

When a signal goes up and returns by ionospheric refraction, the situation changes. The article on Faraday rotation explains that although most transmitting antennas are either vertically or horizontally polarized, the polarization of a medium or short wave signal after reflection by the ionosphere is rather unpredictable. At microwave frequencies the effect is much weaker, which is why satellite links keep their polarization between the satellite and the ground.

The practical consequence is that, for DX on skywave, the nominal polarization of your antenna is much less important than its takeoff angle, gain and height. A horizontal beam and a good vertical can both work the world. The same page goes further. In its discussion of diversity it argues that mixing horizontal and vertical antennas does not reduce fading on skywave paths: combining two sources of different polarization simply produces a single tilted polarization, and skywave signals have several paths with varying phase delays that are as likely to subtract as to add. Circular polarization, it says, costs 3 dB when mixed into a linear system and tends to increase fading on skywave paths rather than reduce it. The lowest-fading antenna, it concludes, is one with a single polarization focused as cleanly as possible at the best wave angle and compass heading.

What matters for HF DX is therefore low radiation angle and a good ground system for verticals, or height and gain for horizontal antennas. For a first antenna, read our comparison of the first HF antenna choices.

Where the Choice Is Practical

Two of these rows rest on conventions rather than physics. Over a line-of-sight VHF path, either polarization propagates well, but everyone benefits when stations in the same part of the band use the same polarization. The usual habit is vertical for FM and repeaters, since handhelds and mobiles carry whips, and horizontal for weak-signal work on SSB and CW. If you start working the bands above 50 MHz, find out what your local group uses. Our 6 metre band guide shows how horizontal polarization suits long-distance openings on that band.

Mismatch Loss and Tilted Antennas

If the transmitting and receiving antennas are cross-polarized, the received signal falls sharply. The antenna article says the loss rises with the angle between the polarizations, and the W8JI page notes that a receiving antenna tilted 90 degrees from the maximum response gives a near-zero result. On a clean line-of-sight path the loss can be very large, which is why a handheld held sideways can surprise you on a weak repeater signal. In practice, reflections, scattering and tilted antennas keep the loss well below the theoretical maximum on real paths, but the effect is still noticeable on a quiet band.

That is also why you should not put every antenna in the same orientation by habit. Check how the other stations on your favourite net or mode are polarized, and choose to match them if you want the strongest signal. If the polarization is uncertain or changing, as with a satellite whose orientation varies, a circularly polarized antenna avoids deep fades from mismatch at the price of 3 dB. The details are in our guide to getting started with amateur radio satellites.

Choosing for Your Station

• Limited space, regional contacts on low bands. A vertical with a proper radial system is a strong performer, particularly at low angles.
• Medium height and a wire in the trees. A horizontal dipole is simple and effective, and its pattern improves with height.
• DX on 20 m and above. Either works. Choose according to space, noise and height. Verticals often hear less man-made noise in some locations, while horizontals often have an easier time on the receive side in others.
• VHF and UHF FM. Use vertical polarization for repeaters and local nets.
• VHF and UHF weak signal. Use horizontal polarization, and be ready to change if the local group does otherwise.
• Satellites. Use the antennas recommended for the satellites you want to work.

When Circular Polarization Makes Sense

Circular polarization is not a cure for fading on HF, but it has a clear place at higher frequencies. In a circularly polarized wave the field rotates once per cycle, so the wave carries every linear orientation in turn. A circular antenna therefore receives either vertical or horizontal linear signals at the same 3 dB penalty, which makes it a sensible compromise when you cannot know or control the other station’s polarization. Satellite links are the classic case. At microwave frequencies the polarization survives the trip between the satellite and the ground, but the satellite’s own orientation may change as it moves, so an antenna that does not care about the angle helps. Be aware that a circular antenna is blind to a circular signal of the opposite sense, so the handedness has to match, and that mixing a circular antenna into a linear HF system just wastes 3 dB.

Practical Tips for Handhelds and Mobile Stations

• Hold the radio upright. A handheld whip is vertical when the radio is vertical. Tilt it and you add cross-polarization loss against a vertical repeater antenna.
• Mount mobile whips vertically. A leaning whip changes the polarization and the pattern.
• Use a proper ground plane. A vertical on a small metal surface or a vehicle roof behaves differently from one on a mast, as the dipole article notes about monopoles and their ground.
• Test before you blame the antenna. Turn the handheld on its side for a moment and compare the signal reports. The change tells you how much polarization matters on your path.
• Choose antennas for the band plan. The IARU band plans explain which segments of the VHF and UHF bands are intended for FM and which for weak signals.

Common Mistakes

• Believing that vertical polarization is only for local contacts. A good low-angle vertical works DX on skywave.
• Assuming horizontal antennas are always quieter. Noise depends on your environment more than on polarization.
• Ignoring the ground. Both polarizations depend on it, in different ways.
• Mixing polarizations on one beam to cure fading. The evidence points the other way.
• Holding a handheld at an angle. Keep the whip vertical when talking to a vertical repeater antenna.

The Bottom Line

Polarization is decisive on the ground wave, where vertical wins, and on line-of-sight links, where matching the other station matters. On HF skywave, where the ionosphere scrambles polarization, takeoff angle, height and gain are what count. Pick the polarization that suits your space and the kind of contact you want, build the best ground or the best height you can, and match the convention in your area when you move to the VHF and UHF bands.

Frequently Asked Questions

Does polarization matter on HF?

Much less than on VHF. The ionosphere makes the polarization of a skywave signal unpredictable, so takeoff angle, height and gain matter more than the antenna’s nominal polarization.

Which polarization is better for DX?

Neither by itself. A low radiation angle matters most, which a good vertical or a high horizontal antenna can provide.

Why do repeaters use vertical polarization?

Because handhelds and mobile stations use vertical whips, and matching polarizations gives the strongest signal. It is a convention that everyone relies on.

Do weak-signal stations on VHF use horizontal antennas?

Usually, yes. SSB and CW stations on the bands above 50 MHz generally use horizontal polarization, though practice varies by region, so check locally.

What is circular polarization good for?

A circular antenna receives vertical and horizontal waves equally well at a cost of 3 dB, which suits links where the other polarization is unknown or changing, such as satellites.

What happens when polarizations are crossed?

The received signal drops, more the larger the angle between them, and at 90 degrees the response is close to zero in theory. Real paths with reflections show less loss.