Which type of feedline has the lowest loss at VHF and UHF frequencies?

The type of feedline known for having the lowest loss at VHF and UHF frequencies is air-insulated hard line. This type of feedline is constructed with a rigid outer conductor that is typically made of aluminum or copper and has an air dielectric. The air dielectric reduces the signal loss compared to other materials that might be used in different feedline types, which often have higher dielectric losses.

At VHF and UHF frequencies, signal losses can accumulate significantly due to resistive losses and losses through the dielectric material. The rigid structure of air-insulated hard line also makes it more resistant to environmental factors like moisture, which can further enhance its low-loss performance. This is why it’s commonly used in applications where signal integrity is paramount, such as in broadcasting or in communication systems requiring long runs of feedline.

Other types of feedline, such as flexible coax (both 50-ohm and 75-ohm) and multi-conductor unbalanced cable, tend to have higher losses due to their construction materials and designs. Flexible coax, while versatile and easy to work with, generally has a lower performance than air-insulated hardline because it usually uses a solid or foam dielectric instead of air and can have significant losses over longer lengths or at