clearwire.bmpClearwire, the company that is building WiMax, a new wireless technology boosts the performance of wireless broadband, has raised $600 million in its initial public offering. It begins trading today.

Clearwire, of Kirkland, Wash., reported a net loss of $240 million last year, largely because it is building out its WiMax network, and has yet to start selling it. It remains a big risk. Sprint-Nextel plans to roll out a competing WiMax network next year, and there are many other competing offerings outside of WiMax.

WiMax differs from WiFi in that it has much longer ranges — as much as 10 miles vs. WiFi’s reach of a few hundred feet.

The IPO priced this morning at $25 a share, at the top of its planned range. The IPO is signficiant because the stock markets have been jittery lately, the Nasdaq having lost more than 6 percent of its worth since WiMax filed its IPO papers. Telecom IPOs have been rare. Clearwire’s biggest backers are Motorola ($300 million invested) and Intel ($600 million invested)