April 28, 2026 – Let’s Talk about Base Station Feedlines

Good evening. This is W1UT and tonight’s training is about “Base Station Feedlines.”

This training topic is about selecting a suitable coaxial feedline for your VHF/UHF base station.

The device between your base station radio and the antenna is called a feedline or transmission cable and its purpose is to get your signal to and from the antenna – usually with little loss. Just about all VHF/UHF feedline these days uses 50 ohm coaxial cable. Coaxial cable, or coax, is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric material. Over the outer shield is an outer sheath of protective material. This type of coax has been around for a long time pre-dating WWII. Not all coax has the same characteristics. Coax often used at repeater sites use what is called hardline coax where the inner conductor is typically solid copper or a copper plated conductor and the outer shield is also copper material of various configurations. This type of feedline is very expensive requiring special connectors and difficult to work with. However, it also has the least signal loss especially for long runs. It is also very rugged and best able to survive mountainous environments.

Most amateur radio base stations will utilize coaxial cable that has an outer shield consisting of braided wire. There are many types of this coax ranging from small diameter RG316 cable to ~½ inch diameter cable with far lower RF losses such LMR600. Cost per foot of coax is generally directly proportional to the thickness of the cable and the materials used in its construction. RG58 50 ohm cable is often found in mobile installations, but has significant losses on VHF and especially UHF. This is suitable for mobile installations as the length of the feedline is usually less than 20 ft. You can use this type of cheaper coax for a base station if the run between your radio and the antenna is short.

The best coaxial cable for a base station up to around 100 ft is LMR400 type of feedline. Based on this you might want to choose a location for your base station and/or your antenna that results in a short run of feedline. If you install an antenna on say a 100 ft tower that is 50 ft from your home even LMR400 may result in too much signal loss. Manufacturers of coax have loss charts indicating how much loss for 100 ft or meters their coax has. A cable with a loss of 3db means that one half of your transmitted and received signal will be lost. This is significant but can be helped by installing an antenna that overcomes feedline loss due to its gain.

You can buy coaxial cable with 50 ohm connectors installed or do the installation yourself. Make sure the radio mating connector is a male PL259 or suitable N type male connector. The same type needs to be installed on the antenna end. Make sure the antenna end connector is properly weather sealed. Those who are serious operators often will install a gain type of antenna that has an N connector. These types of N connecters have less loss and are more resistant to weather. However, it is recommended that all outside connectors be properly sealed against moisture. Moisture resistant methods to do this can be found on the internet.