DX Engineering 300 Ohm Ladder Line

DX Engineering 300 Ohm Ladder Line is a transmitting grade low-loss parallel-wire RF feedline featuring a strong, waterproof, UV black polyethylene insulation. To maintain the wire spacing between the conductors while reducing losses, the integral flat plastic material alternates with rectangular openings, which explains the "Window Line" nickname. Capable of handling over 2.5 kW of RF power, DXE-LL300 is a very low-loss transmission line across HF that is ideal for long feedline runs. It is an excellent feedline choice for a low band non-resonant wire antenna operated on multiple bands on which the impedance varies significantly, causing mismatches and elevated SWR. Unlike coaxial cables, DX Engineering DXE-LL300 Ladder Line maintains low RF losses at frequencies where impedance mismatches cause high SWR. The lower impedance of DX Engineering 300 Ohm Ladder Line is actually better suited than 450 ohm ladder line for limiting the impedance extremes of non-resonant multiband antennas. It can provide significantly higher efficiency than coaxial cable for feeding non-resonant antenna systems that are matched with a wide impedance range antenna tuner.

DXE-LL300 Ladder Line is a flat, high-quality RF feedline, about 0.438 in. wide with two 18-gauge copper-clad steel wire conductors that provide the strength to hold up for long spans between supports without twisting. It exhibits a nominal impedance of 275 Ohms and a nominal Velocity Factor of 88 percent.

For proper performance, LL300 Ladder Line must be installed suspended through the air supported by insulators every 25 ft. or less, kept at right angles and several inches away from other wires, and at least one foot away when run parallel to the earth or large metal surfaces. Installing with an axial twist of one turn per 10 ft. can reduce wind, rain and ice loading, RF coupling and RF noise. DXE-LL300 can be mounted with insulators and suspended on metal or wood posts or run along a wood fence line, only if the fence has no wires or metal mesh that couples RF noise or unbalances the feedline.

Most often used for non-resonant wire doublet antennas, dipoles, and inverted-vees, DXE-LL300 can be more easily terminated outdoors to a DXE-MC20-1-1T 1:1 Balun. Then, with no inline switches or relays, directly connect the antenna system to a typical indoor wide range antenna tuner using a solid dielectric coax instead of foam dielectric, to handle high voltage at high SWR. DXE-213U or DXE-214 Coaxial Cable Assemblies 12 or 18 ft. with PL-259s are perfect for this method, which eliminates the need for a special balanced tuner, and avoids the losses and detuning effects caused by unbalancing when ladder line is routed indoors near wires and ducts.

DXE-LL300 is sold by the foot, previously sold as DXE-LL300-CTL, this is the same ladder line with a new part number. It is also available in spools of 500 ft. DXE-LL300-5C and 1,000 ft. DXE-LL300-1K.

NOTE: This type of feedline is intended for MF and HF use and is not suitable for use above 30 MHz.
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