The Yagi directional antenna is named after the Japanese inventor who designed it. A simple, three-element antenna can be built from a coat hanger or household copper wire. The elements will be sized based on the frequency you select for signals. The homemade build-out includes assembly steps, outdoor mounting, coaxial cable line connection and lead-in, and elevation and direction (azimuth).
- Skill level:
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Things you need
- Two 6-foot spruce planks, 2-by-4 inches
- Table saw
- 14 gauge electrical copper wire, 11 feet (Romex electrical wiring)
- Silicone glue tube
- TV 300-ohm twin line, 6 feet long
- RG59U coaxial cable (length to be determined by location of receiver)
- Matching balun coil
- Wood screws
- Drill and bits
- 10-foot section of 3/8-inch mast
- U bolt, nuts and washers, 3/8 inch
- Wrenches or common pliers
- Electrical tape
Cut the 6-foot spruce pieces on a table saw into 2-by-2's. Quarter two of these into 1-by-1-inch pieces. Cut the boom length at 143cm. This is the centre piece for the addition of the three elements. Take the 1-by-1-inch strips and cut the reflector (back) to 162cm, the driven element (middle) to 160.3cm and the director (front) to 146.cm.
The spacing between reflector and the driven element is 89.2cm, and the space between the driven element and the director is 48.7cm. Screw and silicone the elements in place and let dry.
(Note: The Yagi here is for the FM radio band, and these dimensions are sized accordingly.)
Add 14-gauge copper wire to both reflector and director elements, the full length of the pieces. Screw and silicone in place.
The driven element requires a full length of TV twin line. Cut and solder the ends together and attach to the element with screws and silicone. Cut one side of the twin line at the centre or middle and attach balun coil by soldering it in place. Cover the connections with silicone. Later, when the antenna is in place, the coaxial lead-in will be attached to the open end of the matching balun coil.
Add the mast at centre of the boom with a U bolt joining the two pieces. Drill holes into the boom to fit the U bolt in place and attach the antenna in a horizontal plane perpendicular to the mast.
Mount the mast with the antenna on your roof as high as possible and away from reflective interfering objects. You can also attach the mast to a sturdy object like a chimney with kits available at electronic supply houses. Establish the direction (azimuth) of the antenna with the director element pointing directly to the prime station of interest. You may wish to mount the mast for ease of changing direction or add a motor and rotor combination for frequent redirection.
Connect the coaxial cable to the mounted antenna balun coil. Tighten snugly with pliers. Connect the cable to the mast, allowing a foot or two extra to act as a strain gauge for the connectors on the antenna. Tape the balun and connectors in place to the antenna. Run the coaxial cable directly to the radio. Avoid coils and unnecessary lengths. Add cable mounts to secure in place.
Making and Mounting a Yagi Antenna
Tips and warnings
- Varnish wood parts of antenna to protect from weather.
- Add small pieces of wood to secure element connections. Use silicone to glue in place.
- Your mast is a lightning hazard. Add a lightening arrester and run to the ground.
- Avoid antenna work when weather threatens.
- Most lumber yards will cut your wood pieces to size. Be happy with 1-by-1's and cut fractional centimetres yourself.
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