If you have an FM receiver with a jack for an external antenna, you'll note that the jack is usually specified for 75-ohm antennas. If you're unfamiliar with an antenna design, building an antenna that will work at a specific resistance may seem like a difficult task. But it actually isn't--you can build an antenna that works with a 75-ohm input fairly easily and inexpensively.
Cut a 30-inch length of 300-ohm twin lead cable. Don't be concerned that the cable is a 300-ohm cable and you're making a 75-ohm cable. The cable is merely used as the active element that receives the signal.
Remove 1/2 inch of insulation from the both ends of the cable. Twist together the separate leads at each end of the cable.
In the middle of the cable, cut one of the two elements of the cable and remove 1/2 inch of insulation from either side of the cut with your wire strippers.
Solder each bare wire from the middle cut to one of the tabs of a 300- to 75-ohm transformer.
Connect one end of the coaxial cable to the transformer by plugging it in.
Connect the other end of the coaxial cable to the antenna input of your receiver.
300-ohm to 75-ohm transformers can be bought at most electronics supply shops.
Things you need
- 300-ohm twin-lead cable
- Wire cutters/stripper
- 300- to 75-ohm transformer
- Soldering iron
- 75-ohm RG-6 coaxial cable with F-Type connectors