If you're looking for instructions on how to build a radio antenna, it's likely because you're trying to increase the range of a handheld two-way radio, mobile radio unit or radio base station. The two primary factors in increasing a radio's range are the radio's output power and the antenna. In this article, we'll give a quick radio antenna primer, important factors to consider for the best radio antenna for your two-way radio and the basic steps in building a simple monopole antenna.
Radio Antenna Basics
During the process of transmission, the purpose of a radio antenna is to convert electric power into radio waves and radiate those waves into the atmosphere. For reception, the process is handled in reverse, with the antenna intercepting the power of the electromagnetic wave, producing a voltage that is sent to a receiver and amplified. There are different types of radio antennas, including monopole, dipole, array, loop, aperture and traveling wave. Two-way radios use Monopole Antennas, with the Whip Antenna and the Rubber Ducky antenna being the particular types you find on handheld radio units. Ground Plane Antennas (a whip antenna with horizontal rods at the base) are used as antennas for radio base stations.
Antenna Considerations and Placement
Before building an antenna, it is important to understand your radio's abilities and limitations. It is obviously not possible to use a handheld two-way radio with an external antenna, because you're always moving around.
If the two-way radio is to be used exclusively inside your vehicle, you will need an external antenna, since the metal of the vehicle will interfere with the radio waves. In this case, you could build an external antenna and mount it on the vehicle's trunk, but it is very important to match the antenna with the radio's frequency. For a quarter-wave monopole antenna, the length of the antenna is .25 percent (1/4) of the wavelength of the frequency you're transmitting on. If you're using a radio base station, you can use an external antenna which would be placed on top of the roof or a tower for maximum effectiveness. The higher the placement of the external antenna, the greater the range of your transmissions.
Best Antenna Materials
While antennas can be made from different kinds of metals, some are more conductive and less likely to corrode over time. Though inexpensive, aluminum antenna wire is not recommended, because it is difficult to work with, can break or stretch out of shape easily and can't be soldered with standard solder. Tin wire can be used for making an antenna, but you usually have to purchase it in very large quantities. Copper is an excellent choice for antenna wire. If you can find old insulated copper house wire, this is likely your best option.
Basic Instructions for a Simple Monopole Antenna
Please note that this basic instruction is for a desktop two-way radio such as a Ham radio with a built-in tuner. An external antenna for a mobile unit or base station must be sized according to the particular frequency's wavelength. These simple radio antenna will require the following materials: a 1-inch thick, approximately 3 foot long round dowel or broomstick; a sturdy wooden base; a 6- to 12-inch aluminum disk with center screw hole; a large quantity of .16-inch PVC plastic covered wire and PVC tape. You'll also need nails or screws, a wood staple, a hammer and screwdriver.
- Attach the base (square or round) to the dowel, using a nail or screw. Wood glue can be used to make it more stable.
- Attach the aluminum disk to the top of the dowel. Strip the end of the PVC wire and place it between the top of the dowel and the aluminum disk. Tighten the disk to the dowel using a screw or nail. The stripped wire must be securely in between the 2 pieces.
- Take the wire and tightly wind it around the dowel, keeping the wire coils flush against each other and wound tightly around the entire dowel all the way down to the base. Using the wood staple, attach the wire to the base.
- Wrap the dowel with the wound wire completely with the PVC tape.
- Place your newly made antenna near a window.
- Keep unraveling the wire at the bottom until it's long enough to connect to your two-way radio tuner. It is now ready to use.
Antenna Building Resources
To build a properly sized and tuned antenna for a mobile two-way radio or radio base station, the instructions are obviously lengthier and more involved than this brief article allows. However, there are excellent resources for those wishing to learn more.
The ARRL Antenna Book (published by the American Radio Relay League) - The ARRL was founded in 1914 and is the national association for amateur radio in the U.S. It is the world's largest organization of radio amateurs, and they offer many excellent guides that focus on specific radio communication topics.