A high-gain FM antenna often requires a lot of space, as the receptors on the antenna must be cut to match the FM frequency range. This typically creates quite long arms, but by constructing an antenna in a slightly different shape, it's overall size can be significantly reduced while still enjoying excellent reception. A dipole FM antenna provides this combination of reduced size and high efficiency, and can easily be constructed from readily available components.
Things you need
Wire coat hanger
30 cm by 10 cm (12 inch by 4 inch) piece of card
15 cm (6 inch) length of 10 mm by 25 mm (3/8 to 1 inch) sawn wood batten
Wood screws with metal washers
Squash the wire coat hanger carefully, bringing the hook toward the long, straight bottom of the coat hanger until the sides are parallel with the bottom. Be careful not to bend the bottom of the coat hanger. Cut the hook off using the wire cutters, just below the neck where the wires are twisted together.
Bend the two end pieces of wire (where you just cut off the hook ) into small hooks using the thin-nosed pliers. The two hooks should be between 15 mm and 20 mm (5/8 and 25/32 inch) apart.
Screw the coat hanger horizontally across the top of the batten, creating a "T" shape. It should be positioned approximately 5 cm (2 inch) from the top of the batten. Screw through the small hooks made in the ends of the coat hanger to attach it to the batten, but don't fully tighten the screws.
Strip 10 mm (3/8 inch) of sleeving off the end of each piece of wire on the 75-Ohm balun, if it doesn't have terminals or spade connectors already fitted. Place one wire or connector under each screw on the batten, and tighten them down against the coat hanger.
Cover the piece of cardboard in kitchen foil, taping it down on the reverse of the card. Tape, staple or screw the foil-covered card to the opposite side of the batten to the coat hanger. Position the card so the coat hanger is aligned horizontally along its centre. This will act as a reflector, to increase the antenna's efficiency.
Connect a TV aerial lead to the balun, and the other end to your TV or radio receiver. If connecting to a radio, you may need to cut the connector off and strip the wires back to connect the lead to screw terminals. Consult your radio's instruction manual for details on antenna connections.
- The length of batten protruding from the bottom of the antenna can be used to fix a base. The balun is required to match the antenna to a standard TVs or radios. The antenna will not function correctly without it. A balun can be acquired from most electronics suppliers, and will be fitted with a standard coaxial connector for connecting to a standard TV or FM lead.
- Ensure the reflector isn't making contact with the coat hanger, as this will significantly impede its efficiency.
Things you need
- Wire coat hanger
- Wire cutters
- Thin-nosed pliers
- 75-Ohm balun
- 30 cm by 10 cm (12 inch by 4 inch) piece of card
- 15 cm (6 inch) length of 10 mm by 25 mm (3/8 to 1 inch) sawn wood batten
- Kitchen foil
- Electrical tape
- Wood screws with metal washers