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What is a Helix Antenna?

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  • Written By: T. L. Childree
  • Edited By: Jenn Walker
  • Last Modified Date: 28 August 2016
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A helix or helical antenna is a type of antenna that utilizes a conducting wire wound in a spiraling helix shape mounted over a ground plane. A helix antenna is a type of directional antenna — the electromagnetic field typically rotates around the axis of the helix in either a clockwise or counterclockwise direction. Simple and practical, helix antennas were essentially designed to take the place of much larger antennas while maintaining the same wide bandwidth characteristics. A helix antenna is most often used with hand held satellite communication devices such as telephones, radios, and Global Positioning Systems.

A helix antenna is usually able to provide superior reception in instances where the receiving device has a poor view of the sky, such as under tree cover and in the midst of tall buildings. Its ability to lock-on to the greatest number of satellite signals at one time also provides more accurate reception when traveling in vehicles, and it will likely be pre-installed in future automobile models.

A helix antenna is capable of being operated in one of two main modes: broadside, or normal, mode and axial, or end-fire, mode. Broadside-mode helical antennas are generally used in situations where a smaller antenna is an important operational factor. These antennas were first used with Citizen’s Band radios in the US and Australia during the late 1960s, and are widely used today as typical FM receiving antennas in automobiles.

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Axial-mode helical antennas are more suited for situations in which a fixed orientation of transmitter and receiver cannot be easily obtained. This type of helix antenna is most often used in satellite communication devices, such as telephones and Global Positioning Systems. When an axial-mode helical is used, both the transmitting and receiving antennas must have the identical handedness for optimum results.

In geometry, a helix is defined as a smooth three-dimensional curve with a tangent line that maintains the same constant angle with its fixed axis. A good example of a geometric helix is a coil spring. Helices may be right or left-handed. The handedness of a helix is determined by looking along the axis of the helix and turning it in a clockwise direction. If the helix appears to move toward the observer, it is a right-handed helix, but if it appears to move away, then it is a left-handed helix. A common hardware screw is an example of a right-handed helix.

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hamje32
Post 3

@everetra - I’ve seen pictures of these kinds of antennas and the homespun variety look kind of weird.

They remind me of the parabolic antenna. The parabolic antenna uses a parabola, similar to a small satellite dish, and has the antenna pole fixed in the middle of the dish.

The parabola is supposed to enhance the signal as it comes in and direct it squarely at the antenna pole. I don’t know how well they work, but the concept is similar to the helical antenna in that it tends to make the incoming signal more focused.

everetra
Post 2

@Mammmood - I didn’t realize my GPS unit had any kind of typical antenna until I read this article. I checked, and sure enough it does – but it’s a very small helix GPS antenna.

One thing I’ve noticed with the GPS receiver is that while in general it does get good reception when it goes through its initialization by the satellite, it doesn’t always do well indoors.

I don’t have to have perfect line of sight with the sky, but I can’t be totally covered either. So I turn it on outside and let it wait a few minutes until the satellite locates it and the unit is ready to go.

The helical antenna certainly helps, but it’s still an antenna, and in that regard you need the best positioning possible for ideal reception.

Mammmood
Post 1

If you’re the adventurous type or you’re into HAM radio or stuff like that, you can build your own helical antenna.

The design concept is simple – a pole with wire coiled around it. You can find plenty of sample designs on the Internet and some of these use different things for the pole like a straight metal piece or PVC pipe.

It will take some trial and error to get it right. If you need something for serious purposes then of course I would recommend that you buy a professional helical antenna from the store, or at least get a good book on antenna design and theory.

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