Rigid line is a coaxial line formed by two copper tubes maintained concentric through the use of supports. These rigid lines cannot be bent. Elbow joints are often used when a straight path is not available.
Weatherproof flanges are used with rugged rigid line used outdoors, common with those installed in conjunction with antenna towers and masts. Many times on towers the outer line is aluminum. Aluminum saves on weight and cost. But special attention must be taken to prevent corrosion and oxidation of the aluminum.
Hard line is coaxial cable created by using round copper, silver or gold tubing and/or a combination of such metals as a shield. Lower quality hard line might use aluminum for shielding. This runs a higher risk for oxidization. And unlike silver oxide, aluminum oxide will drastically reduce the conductivity of the hard line. Due to the risk of oxidation, all connections must be air tight and water tight.
Rigid Line to Hard Line
It is possible to go from a rigid line to a hard line. Using a flange connector, many broadcasting antennas and antennas splitters use the flanged rigid line interface to connect to flexible coaxial cables as well. The ability to connect cables gives an installation team options when working through indoor/outdoor scenarios or transitions above/below ground.
Rigid Line Maintenance
As previously mentioned, all joints need to be air and water tight to ensure oxidation of the coaxial cable does not occur or is minimal. When a rigid line is damaged due to age or weather, the line needs to be repaired. Ensuring your rigid line joints, flanges and interfaces (if applicable) are in good condition will ensure the highest performance of the coaxial cable it protects.