Clearwire, the wireless broadband provider backed by Craig McCaw, has once again filed plans to raise $400 million in an initial public offering.

But this time, the Kirkland company has a lot more cash in the bank and thousands more subscribers and is operating in more markets.

If successful, Clearwire's IPO would be the second largest in Washington after AT&T Wireless, which raised $10.6 billion in 2000.

Clearwire filed its first IPO documents in May but dropped the plan two months later after Intel and Motorola invested about $1 billion.

As part of that deal, Motorola bought Clearwire's equipment subsidiary, for a previously undisclosed $47 million.

The proceeds of the planned IPO will be used to roll out wireless broadband networks based on the emerging WiMax technology.

WiMax, and the proprietary technology Clearwire uses today, allows high-speed Internet access to be delivered through the air, instead of through cables or copper lines.

Today, Clearwire serves 34 U.S. markets, covering 8.5 million people, and has service in areas of Belgium and Ireland. Its biggest market launched last month in Seattle, where it will have to prove it can deploy the technology on a large scale.

As of November, it had 188,000 subscribers, compared with 88,000 when it last laid out plans to go public.

The company previously raised about $2 billion in private equity and debt, but its long list of expenses will require a lot more.

For instance, in each market, Clearwire must build a matrix of antennas to provide coverage.

It also must acquire spectrum, the airwaves the signals utilize, and it must heavily market its brand.

Loss recorded

The company has about 1,200 employees, 900 in the U.S. It reported it lost $191.9 million on revenues of $76.4 million in the first nine months of 2006.

The $400 million from the IPO, along with $1.3 billion in cash and equivalents, will be enough to support the company for the next 12 months, the filing said.

Shares will trade on the Nasdaq Stock Market under the ticker "CLWR."

The company was founded by McCaw, the wireless entrepreneur who started McCaw Cellular Communications; it later became AT&T Wireless.

Despite Clearwire's need to raise capital, McCaw intends to hold a tight grip on the company's future.

After the public offering, control will remain in the hands of both McCaw and Intel due to a two-class stock structure in which they hold shares with 10 times the voting clout of the shares being sold to outside investors.

The filing also provided a rare update to an otherwise close-mouthed company that lets its marketing via direct mail and radio commercials speak for it.

Increase in spectrum

Among other details in the 1,873-page document, Clearwire reported it had increased its spectrum holdings in the U.S. to cover about 205 million people, and believes it owns the second-largest amount after Sprint Nextel.

It also said that by the second half of next year, it will replace the bulky modem required to receive Clearwire coverage with a PC card.

The company said it is also offering voice over Internet Protocol in 13 markets and that other services and applications are in the works.

Tricia Duryee: 206-464-3283 or tduryee@seattletimes.com