Replacing coax cables | LMR-400 or LMR-240 Transmission Line
Replacing a coaxial cable transmission line is a tough job and one that gets put off as long as we can! When fresh coaxial cable runs are installed they can perform perfectly, especially if they are the newer LMR cables rather than old RG-8 or 213. Water penetration, shielding loss and jacket abrasion will cause even the best coax to degrade over time. Many operators may not notice the slow decline of their ability to make contacts as less signal is carried through the coax to the antenna. Even though LMR-400 or LMR240 can last twice as long as the old RG, during installation of your transmission line take a few basic precautions to slow or prevent it’s decay.
By correctly installing a RF coax cable it can provide many years of satisfactory service. However wear, and exposure to the elements will mean that after some time it may be prudent to replace the RF coax cable. Operators may not realize the full extent their coax has allowed signals to degrade as loss occurs over a long slow period. As coaxial cable runs are replaced by newer cable users can see a nice increase in contacts.
One of the first steps is to read the specifications sheet for your cable type. Each manufacturer has it’s own standards defining bend radius. Kinking or bending coax sharper than the bend radius will damage the dielectric and result in increased transmission loss. If RF coax cable is bent beyond its limit then damage to the inner core of the cable may result. Kinking and sharp bends during install will cause permanent loss even after the coax is straightened.
Selecting a better quality longer lasting cable from Times Microwave can make installation easier. Even though the LMR series coaxial cables can bend in as little as 1 inch without attenuation, each manufacturer has it’s own standards defining bend radius. Don’t damage your coaxial cable assembly during installation by bending in a sharper curve than defined or you will cause higher VSWR and increased loss. Exceeding the bend specs will ensure poor service and shorter coax cable lifespan. Improper installation will result in much less performance than the design specifications.
Take care during coax installation to ensure that the cable is not crushed, or likely to be crushed. If RF coaxial cable is damaged in this way, the dimensions of the cable and dielectric are changed and it will not maintain the characteristic impedance. If the dielectric between the two concentric conductors in the coax cable is damaged, there is an increase in the level of loss.
Kim has been operating her cable business on eBay (SageMaiden) and Amazon for years selling only custom Times Microwave LMR-400 US Made coax cable assemblies. With thousands of cables sold and top-rated status on eBay she is setting up her first ecommerce site at http://USACoax.com as the title says, only US made coax with no Commie Cable sold! Before buying cable see her other articles: LMR-400 50ohm & 75 Ohm | Coaxial Cable and Transmission loss
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