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EspañolTWIN-LEAD
'Twin-lead' is a two-conductor ribbon cable of 300 ohms characteristic impedance commonly used as a transmission line for balanced connection of television antennas to their receiving antennas.
It has the advantage that it can be connected directly to a suitably designed dipole (~75 ohm resonant impedance, or a folded dipole with a better match at 300 ohms), yagi or similar balanced antenna, and was almost universally used for feedlines to outside antennas in the days of black-and-white television. However for colour television installations it has been largely replaced by 75-ohm coaxial cable.
In domestic television installations, a balun with a 4:1 turns ratio is commonly used to match twin-lead to 75-ohm coaxial cable.
It has the advantage that it can be connected directly to a suitably designed dipole (~75 ohm resonant impedance, or a folded dipole with a better match at 300 ohms), yagi or similar balanced antenna, and was almost universally used for feedlines to outside antennas in the days of black-and-white television. However for colour television installations it has been largely replaced by 75-ohm coaxial cable.
In domestic television installations, a balun with a 4:1 turns ratio is commonly used to match twin-lead to 75-ohm coaxial cable.
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