450 Ohm Ladder Line

This is a type of twin lead wire used as a transmission line to carry radio energy. It is constructed of two multi-stranded copper or copperclad steel wires, held a precise distance apart by a spacer ribbon. The uniform spacing of the wires is the key to the cable's function as a parallel transmission line. If the spacing is not maintained then rf energy is reflected backwards to the transmitter.

Traditional VHF television installations from prior to the digital conversion used 300-ohm ladder line. The standard in HAM radio for HF operation is 450-ohm. This is a measurement of the impedance of the line. As a transmission line, transmission efficiency will be maximum when the impedance of the antenna, the characteristic impedance of the twin-lead line and the impedance of the equipment are the same.

• 450 Ohm Ladder Line is a type of balanced line
• Coaxial cable is a type of unbalanced line.