A helical antenna is constructed from a wire that is wound to form a coil or a helix. Here's how to build one.
- Prepare the necessary materials. Acquire standard household wiring with a size of 12 gauge or 14 gauge. The wire's diameter is not a crucial factor in the antenna's performance. However, since the antenna may be placed outdoors, it has to be as sturdy and heavy as possible hence the size. The length should be enough to be wound around the length of the antenna column. Additionally, a PVC pipe with a length of 40cm and a 40mm diameter will be used to wind the wire around it. Other materials that have to be purchased from the hardware store are a metal mesh for the ground plate; an impedance stub made up of a strip of copper foil that is shaped in a triangle with dimensions of 17mm in height and 71mm in length; a male coaxial cable; screws to secure the antenna onto the ground plate; a PVC end cap that will fit the size of the pipe; one plug cap to be used to cover the pipe's end; and some PVC cement. Have screwdrivers, an electric drill, and a soldering iron within reach during set up.
- Mark the PVC pipe. On the PVC pipe, outline the coil path that the wiring will follow. Make sure that the coil's spacing is equal all throughout at 3cm. To be sure that your Helical antenna is optimized, consider making 12 turns around the pipe.
- Wind the wire correctly. Wrap the wiring around the PVC pipe making sure you follow the markings you previously made. Do not forget to set aside enough wiring off the end to make room for a secure attachment of the copper foil. Solder the wire end onto the narrow tip of the copper foil to join them together.
- Do the finishing touches. With the use of an electric drill, make a hole in the end cap for the connector's attachment. Afterwards, attach the end cap onto the ground plate using screws. Put some PVC cement both on the end cap and the pipe and securely slip the pipe in. Make sure that the copper foil stub is sticking out of the end cap's drilled hole for the connector. Attach the copper foil to the connector's center pin with the use of a soldering iron. Afterwards you should screw the whole structure to the ground plate.
Helical antennas can be made to function either in normal or axial modes. A helical antenna will work in the normal mode if its dimensions are much smaller compared to the actual wavelength of the signal. Meanwhile, if the antenna's dimensions are equivalent to or greater than the signal's wavelength, then it will work in the axial mode. A Helical antenna in axial mode is much more efficient and reliable in capturing a wide variety of signals as compared to the normal mode.