What is Hardline and Semi-Flexible Hardline?

What is Hardline and Semi-Flexible Hardline?

Hardline is a variety of low loss coaxial cable which is useful in satellite communications in amateur radio when the received signals are of low intensity. It is also used in high power broadcast applications to connect the transmitter to the antenna. The shield in hardline may be of copper, silver and even gold tubing or a combination of these metals. Lower quality harlines may use aluminium shielding, but has the disadvantage of losing effective conductivity by oxidation. This would mandate air and water tight connections. Center conductor of the hardline can be solid copper or sometimes copper plated aluminium. Because of these design considerations, hardline is quite thick, usually about half an inch and has poor flexibility for bringing inside the shack through wall conduits.

One of the commercial varieties is known as Heliax. Semi-flexibile hardline can be made with corrugated copper or aluminium shields. Dielectric used in hardline may be polyethylene foam, air or even pressurized gas like nitrogen. Thicker varieties, obviously for broadcast applications can have copper tubing as the inner conductor. Use of corrugated tubing increases flexibility and reduces the chance of kinking while bending. But these varieties are not needed in typical amateur radio applications with much lower power than in broadcast applications.