Posted by Declan Horan on Tuesday, March 22, 2011
Caution!
When purchasing coaxial cable be aware that a lot of what is currently on offer now has minimal copper content. This especially applies to RG213 which now commonly comes with a copper clad aluminimum braid rather than a copper braid. Some suppliers have not readily disclosed this information to their customers.
The disadvantage is that it is possible when fitting connectors that with repeated flexing of the braid the copper coating will fracture leading to conductivity and impedance discontinuities. Fractured and cracked copper coating can lead to a poor solder connection to the braid if you use solder type connectors. If the coaxial cable is subjected to flexing during normal use such as for field days the copper coating on the braid can fracture. This can also happen during installaton of the cable or on retractable or tilt-over masts. Remember skin effect from your RF theory! Ok, so you shouldn't have any RF current flowing on the braid of your coaxial cable but fractured copper coating can still lead to impedance discontinuities.
When purchasing coaxial cable the price usually is the give away but not always. It is always worth checking with your supplier to be sure that you are getting a coaxial cable with a 100% copper braid.