Shielding protects microcell radiosShielding protects microcell radios

Los Gatos, CA--Ricochet, a division of Metricom Inc. has developed a wireless modem and Internet service for on-the-go-professionals who use laptop computers. The service allows access to the Internet, e-mail, the World Wide Web, intranets, and various on-line services. Subscribers benefit from wired phone modem performance--without a phone line or phone jack.

Microcell radios, most often attached to the tops of light poles, provide the building blocks for the wireless network. Helping to cement those building blocks was the RTP Co. (Winona, MN) and Wright Engineered Plastics Inc. (Santa Rosa, CA). Working together, the two companies met the material requirements needed to keep the microcells op-erating in all kinds of environmental conditions, in-cluding shielding against electromagnetic and radio frequency interference (EMI/RFI).

RTP's 2800 Series (olefinic thermoplastic elastomer) specialty compound met the needs for a soft, pliable gasket material for the radios. The gasket fits snugly into the microcell housing to seal off the sensitive inner communication components. It also provides shielding in the joint between the two metal halves of the housing, protecting internal electronics from EMI/RFI.

Because Metricom's radio operates outdoors, the application demanded extreme environmental resistance. Not only does the compound resist chemicals, typical of olefinic elastomers, it can be designed in various hardnesses to fit a specific customer's need, especially in the case of Metricom.

For instance, Matt Casebolt, an engineer at Metricom, had little luck with other compounders before turning to RTP for help. "Within three weeks of my inquiry, I had a sample and tensile specs on my desk," he notes. "I was pleasantly surprised with the attitude and speedy response from RTP."