A typical messenger cable construction is shown below. The messenger wire shown at the top of the cable provides the strength needed for the cable to run a span. As a result, the type of material used in the messenger wire has almost exclusive control over the strength and elongation properties of the entire cable assembly.

Belden 1619A messenger cable construction.

In Belden messenger cable for broadband applications, a zinc - coated (galvanized) 1018 carbon steel messenger wire is used to provide excellent breaking strength. The table below shows that this material exhibits greater breaking strength than the messenger wire material used by other cable manufacturers.

The table also demonstrates that larger diameter messengers provide greater breaking strength. More importantly, it points to an advantage of the high - strength steel used in Belden messenger cables: For the same diameter messenger wire, the Belden cables exhibit greater strength.

Conversely, for the same strength, Belden cables employ a smaller diameter messenger wire. This means that - for the same strength cable - the Belden cable can be smaller, lighter, and easier to install than other manufacturers' cable.

The zinc coating plays an important role in maintaining the strength and integrity of the cable. Ungalvanized steel corrodes easily, and could lead to an early cable failure if moisture were to come in contact with the messenger wire.

The table below compares other physical properties of the messenger wire used in Belden messenger cables (0.051 " dia.) to the same diameter wire used by other manufacturers. Note that Belden uses a messenger wire with higher strength and lower elongation. The higher strength means that Belden messenger cable can withstand longer spans and higher loading than the others.

The lower elongation means that as its maximum tension is reached, the Belden cable will not stretch and change its electrical characteristics. By contrast, the other cables elongate by as much as 10%. Since they may exhibit considerable elongation, they should not be used near their maximum breaking strength ratings. That's because the potentially large degree of stretch experienced will cause adverse changes in the cables' electrical parameters long before the cables actually break.

Because the Belden cables experience minimal elongation, they can be used at a much higher percentage of their maximum breaking strength with no adverse electrical consequences.