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Many ground mobile communication systems used outdoors require a rugged flexible cable assembly that can withstand severe crushing or overbending situations, in addition to extreme temperatures. Traditional flexible cables are not suitable for such outdoor use. As a solution, M/A-COM, a Tyco Electronics business, has developed a ruggedized internal wire-wound cable assembly that prevents damage from crushing (stepping on assembly or running over it) during installation and in use, as well as prevents damage from overbending by preventing bends tighter than the minimum bend radius. In addition, it eliminates kinking during installation and averts damage due to overly tight tie wraps.

Other key features of this ruggedized mast cable include improved handling and crush resistance, minimal change in insertion loss, no change in VSWR specifications, and reduced loss (or phase) change after hundreds of unspoolings and respoolings. Plus, it is UV resistant and sealed for outdoor applications.

As with any assembly, the connector must be compatible with the cable. These ruggedized mast cables are offered in several outer diameters, going from 0.25-inch to 1.4-inch, to fill a variety of frequency, loss and power-handling requirements.

Offering 50 Ω characteristic impedance, small cable sizes, such as FE25 or FE29WW, are available with SMA, TNC or type N connectors. While the large sizes, like FE92 or FE98WW, are used with LC, LT or EIA series connectors. Additionally, intermediate cable sizes, like FE56 or FE60WW, are offered with TNC, type N, SC or 7-16 IEC connectors.

According to M/A-COM, to increase the cable's resistance to crushing forces and concentrated loads placed on the cable, it is a helically wound stainless steel spring over the braids but under the jacket (Figure 1). Plus, to withstand the extremes of outdoor conditions, the new mast cables have stranded center conductors and UV-resistant elastomeric jackets. Operating temperature range for this mast cable assembly is -55 °C to 125 °C.

While reliability data is still being collected for this type of rugged cable, the MTBF when calculated using MIL-HBK-216 is more than a million hours, according to M/A-COM. Likewise, flexure is rated to be >100,000 cycles as per MIL-C-87104 specification.

The nominal velocity of propagation is 76%. By controlling the manufacturing process, the manufacturer can supply phase matched/phase tracking sets. Likewise, the insertion loss with frequency for FE39WW with an outer diameter of 0.39-inches is given in Figure 2. Frequency range for this cable is dc to 18 GHz. Typical insertion loss at 1 GHz is 5.881 dB/foot. However, the insertion loss vs. temperature characteristic is the same as any air-spaced Teflon cables with silver-plated conductors, said M/A-COM. Figure 3 depicts power-handling capability for this cable. According to the manufacturer, the cost of this construction cable is about 5% more than standard designs.
Tyco Electronics M/A-COM Products
(978) 442-5000
www.macom.com

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