a. Coaxial cable is a two-conductor cable consisting of a single center wire surrounded by a
tubular metal shield. Most metal shields are braided and insulated from the center conductor by
polyethylene. Some coaxial cables have air dielectrics with the center conductor being insulated from
the shield by polyethylene beads or spiral winding.
b. Coaxial cable is made in several diameters and characteristic-impedance values. A "hard
line" cable is a low-loss, well-shielded coaxial cable, with an outer conductor of solid metal tubing.
c. Coaxial cable is easy to install; may be run next to metal objects, and installed underground
without affecting the loss of performance. Many coaxial cables have greater loss per unit length than
two conductor lines.
Radio-Television Cords. A cord is simple, durable cable, with two or three conductors, used to
transfer electrical current to an appliance or device. The more familiar types of cords are the two and
three conductors, 117 volts utility cords (fig 5-8).
Figure 5-8. At A a two-conductor cord. At B a common three-wire utility cord
a. Basically, cords are not appropriate for transferring alternating current above the audio
frequency range. This is because of dielectric and conductor losses.
b. Only cables designed especially for radio frequencies should be used for such application.