How to choose the best rf test cable(2）？

In summary, increasing the cable diameter may not be an acceptable solution to achieve the required attenuation level. Another way to save costs is to change the center conductor and/or outer braided layer structure. Customizing a solid center conductor will increase the loss by 10-15%, depending on the frequency. However, many single-core central conductors are copper-clad steel silver-plated structures, the best choice for non flexible coaxial cables. Looking back at the flexibility requirements mentioned above, we need high-end copper-plated silver-plated center conductors. A typical way is to replace the solid steel center conductor with harder copper. The bending life and flexibility of some chain conductors will be redefined without affecting the improvement of attenuation efficiency.

Most general-purpose RG cables use one or two layers of silver-plated copper wire braided and wrapped outer conductor. When exploring the improvement of the outer conductor, the manufacturer found the answer from the semi-steel copper sheathed cable. However, for the center conductor, the loss of semi rigid coaxial cable is as low as the use of solid polyethylene. Radio frequency test cable manufacturers are constantly trying to use new braided structures and production methods to achieve extremely flexible coaxial cables.

A flexible coaxial cable that improves overall performance, including attenuation, uses a 50% covered spiral surface as an inner shield to supplement a single wrapping tape. While providing an interface that is more conducive to radio frequency propagation, the spiral facing increases the shielding of the cable also has additional help. However, this structure also has its drawbacks. The radio frequency capability weakens faster with bending. Usually the third flat braid is placed at the lower end of the spiral belt to help solve this problem. Contrary to media applications, the flat braid has a smooth surface like a spiral belt and is more curved. In addition, the flat and spiral braided belt structure can increase the attenuation to 10% according to frequency changes.

All in all, although the three-layer braided cable is more rigid, it can provide stronger attenuation, shielding effectiveness, and longer bending life. However, a closer look at the strength and angle of the braid, as well as strict control procedures, will find that this type of cable also transmits higher frequencies. Under the conditions of meeting the operating frequency and minimum bending radius, it can still maintain its radio frequency performance when the bending degree is greater than that of the RG coaxial cable.

The most effective way to reduce attenuation includes not only improving the braid and the center conductor, but also changing the center structure. Expanded PTFE, expanded PTFE, Huajian PTFE, and expanded polyethylene are all methods used by manufacturers to increase the percentage of air in the media, thereby reducing its dielectric constant. More air usually means a more flexible center conductor for more flexibility. In order to maintain a suitable impedance, a larger center conductor is needed to reduce the impedance and make the loss lower. It is not difficult to find a low loss coaxial cable with a Vp of 90% or higher. Such cables tend to have lower attenuation, sometimes even smaller in diameter and more flexible than solid PTFE with higher loss.

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