Aluminium cable no longer a lightweight

Andrew Australia
By Ben Cardwell, vice-president, Asia-Pacific and China, Andrew
Friday, 01 January, 2010

Telecom operators often find themselves pulled into a polarised situation that includes cost-control and planning for new bandwidth-hungry applications. Across the industry, operators are re-aligning their network strategies to preserve their operating margins.

At the same time, they are upgrading their networks to support more sophisticated delivery of broadband data. In this new paradigm, every purchase is significant.

Those who require proof need only look as far as recent trends in RF transmission line cable.

Transmission-line components are certainly not the flashiest part in a wireless system. Yet they are an essential part of this market’s backbone. These components serve a variety of segments ranging from commercial and consumer to military and base stations.

In doing so, they take many forms ranging from raw cables and individual connectors to complete cable assemblies. RF transmission line cable has taken on new importance as a potential source of CAPEX savings.

As a key component of the signal path, its impact on reliability and, by extension, OPEX costs is even more important.

As a result, wireless operators are looking at RF transmission line cable in a new light, and cable manufacturers, in turn, are giving them something new to look at.

Recent design innovations in RF transmission lines have produced new choices for wireless operators. RF engineers find themselves torn between what has worked in the past and that which appears to be the wave of the future.

On the one side is copper coax cable. With excellent conductivity, copper makes for a dependable low-loss cable. At the same time, the structural geometry makes corrugated copper cable easy to bend in a tight radius, multiple times if necessary, while retaining a high mechanical strength.

This makes it especially suitable for applications that require large diameter cable, such as connecting base station radio units to tower-mounted antennas.

As a result, copper coax has long been held as the industry standard for 50 Ω RF transmission line. One of the first RF transmission line cables deployed by the wireless industry was, in fact, introduced in 1954.

Still, wireless operators are always looking for an edge, especially if it involves improving the bottom line without sacrificing network performance.

Beginning in 2003, market prices for raw copper started to increase significantly. By the beginning of 2008, the cost of bulk copper was higher than that of aluminium, a metal which had long been the standard conductor of choice for high-power utility transmission lines.

Today, copper’s price volatility makes it difficult for wireless operators to accurately budget more than a few months in advance.

Aluminium, on the other hand, is not only less expensive, its price is more stable. In addition, its lower cost has much less scrap value, reducing operators’ exposure to theft, therefore reducing network maintenance costs.

On the practical aspect, aluminium cables are easy to install, given their flexible properties that allow for greater bending and they minimise tower loading. Compared with some copper cables, aluminium delivers lower attenuation, higher crush strength and reduced weight (about a third the weight of copper).

It is also environmentally friendly and ROHS compliant - making it more efficient to recycle - and offers a more stable raw material cost.

In the early 2000s, smoothwall aluminium cable was introduced as a more cost-effective and equally reliable alternative to traditional copper transmission lines.

In addition to CAPEX savings, smoothwall aluminium cable offers lower attenuation than some of its corrugated copper (and aluminium) counterparts.

The two technologies - corrugated copper and smoothwall aluminium - have been available for more than six years now with aluminium slowly gaining traction in the market.

In 2003, sales of smoothwall aluminium cable for RF transmission lines were estimated at less than 1%.

Since then, more and more wireless operators have embraced the technology. Today, a significant quantity of all wireless RF transmission line cable is aluminium and the transition to that metal is occurring worldwide.

Based on the global use of smoothwall aluminium cable and the continued volatility of copper prices, the aluminium cable will continue to gain acceptance as an alternative for feeder cables.

In addition, the development of new connectors and accessories serves to enhance the value-proposition of aluminium cables.

For example, these new series of connectors and accessories are designed to work equally well with either aluminium or copper cables. For operators, this means that the new connectors and accessories will enable them to deploy the solution that best suits their specific environment, while at the same time reducing their stocking inventory.

The ability to deploy customised solutions will become increasingly important as the wireless industry continues to evolve at faster rates. With the emergence of 3G and 4G technologies, networks need to be able to support mobile broadband data, anytime, anywhere.

The increased data rates, lower latency and expanded coverage requirements demand that wireless operators be able to optimise network performance and profitability on a per site basis.

Perhaps more importantly, the introduction of products such as the new connectors and accessories gives RF engineers the flexibility to determine which product works best for a given site and truly optimise the cable to fit the application.

For most applications, aluminium will provide the most cost-effective overall solution.

In specific applications, such as rooftop installations and those with exceptionally tight bends, copper will continue to be the preferred solution.

Although aluminium is poised to overtake copper as the standard for RF transmission cable, copper will continue to play a critical role in the success of tomorrow’s high-speed wireless networks.

As such, with versatile products such as the new connectors and accessories, operators can feel confident that, whether they opt for a copper or aluminium solution, they are getting the best the industry produces.

That confidence translates into higher system performance and lower network deployment costs.

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