Editor’s Note: This is the fourth installment for our “Meet the RF Experts” series in which contributors to the Understanding the RF Path e-book elaborate on subjects in their areas of expertise.
Cables are here, there, and everywhere! We see them around the house. We see them around the office. We see them off to the side of the road, running up massive cell towers. And each of these cables serves a different, but critical purpose—getting information from point A to point B. Of course, that information can range from a life-or-death emergency call to a video download eliciting a much needed LOL.
In this installment, I’ll explore two basic options in RF transmission lines, which are still the backbone of mobile telecommunications.
On the outside, traditional transmission lines basically look the same. They’re typically round and have a black jacket, and even experts in the field can overlook how their subtle internal differences affect how efficiently they transmit information.
Under that black jacket, coaxial cables typically consist of a copper center conductor, a polyethylene foam dielectric, and either a copper or aluminum outer conductor. CommScope employs both outer conductor options in its HELIAX® transmission line portfolio, but the choice of aluminum is not simply a drop-in replacement for a copper outer conductor. We designed our HELIAX FXL® aluminum cables holistically to take advantage of what aluminum can offer: stabile raw material costs, light weight, high flexibility, and theft deterrence.
What you do with a material makes all the difference. CommScope designed its HELIAX FXL smoothwall cables to incorporate aluminum while offering better attenuation than comparable copper conductor cables, which are typically assumed to perform better. The key is the smooth surface of the outer conductor.
The secret is simple—the larger the cable (the distance between inner and outer conductor), the lower the attenuation of that cable. As far as RF power is concerned, smoothwall cables are larger than their corrugated counterparts, despite having the same nominal diameter as a comparable corrugated cable. In the illustration, you can see that the distance between the outside of the inner conductor and the inside of the outer conductor is smaller in the corrugated cable, due to the corrugation itself, despite the two cables having the same nominal diameter.
Without corrugations, the smoothwall cable maintains its larger inside diameter consistently over the length of the cable, resulting in more stable impedance and lower attenuation. Another benefit to smoothwall is that connector attachment is possible at any point on the cable. Peak? Valley? Don’t worry about it! No consideration has to be made as to where on the corrugation the cable can be cut.
Another great feature of the smoothwall design is that every layer of the cable is filled and bonded, creating a monolithic cable structure with unmatched crush and tensile strength, which is completely water-tight. All of these features combine to make what we feel is the best transmission line choice for conventional RF site architecture—HELIAX FXL smoothwall.
So are you a smooth(wall) operator yet?
You can learn more about the many types of RF transmission lines including smoothwall in chapter seven of CommScope’s Understanding the RF Path e-book. Use the link to access the online version or download it as an app from iTunes, Google Play or Amazon.