Sketch of a J-pole antenna
The J-pole antenna is a frequency-sized transmitting antenna, usually shaped like a large "J." The materials used can be any conductive metal, but the most common is copper pipe. The J-pole consists of a primary positive section, with a tunable secondary section attached to the side of the primary shaft, giving it the appearance of the letter "J." A single-frequency J-pole antenna can be built in about two hours.
Instructions
Building a J-pole antenna
1. Determine the length of copper pipe necessary for the frequency of the transmitted radio signal. These frequencies usually fall under "ranges" of an antenna and are called "meters" because of the actual wavelength measurements. To work at peak efficiency, the antenna must be a certain length for a given frequency. Online J-pole calculators can make this process easier (see resources).
2. Cut the copper pipe to the correct lengths with the pipe-cutting tool. The tool will have a sharp wheel that can be rotated around the pipe until it cuts the metal. There will need to be three sections of pipe: one primary, the secondary section and the connector that holds the secondary at a 90-degree angle from the primary.
3. Connect the secondary length of pipe to the small connector pipe with a 90-degree connector.
4. Connect the secondary pipe to the primary with a plastic T-adapter. The secondary should not be grounded to the primary. A small hole can be drilled into the plastic adapter for the wires.
5. Run the wires up through the pipe to the hole in the plastic adapter. The coaxial antenna cable should be stripped, leaving the negative metal shielding and the primary center lead exposed.
6. Solder the positive center lead to the primary copper pipe.
7. Solder the negative shield lead to the secondary pipe. This may require stripping the cable down quite a bit.
8. Apply a liberal amount of electrical tape to the exposed wires and soldered connections.
9. Mount the antenna in an elevated location away from any power lines. Being a long pole, it can be mounted to a chimney or tree with several hose clamps.
10. Test and tune the antenna for proper signal propagation. Transmit on the frequency range of the J-pole and request signal checks or use an SWR meter. The position of the secondary pole can be adjusted with the plastic T-adapter to give optimal signal strength.
Tags: copper pipe, J-pole antenna, center lead, Connect secondary, pipe primary, plastic adapter, plastic T-adapter
