Investors did a double take last Friday when the usual light trading in Clearwire (Nasdaq: CLWR) options was shaken up by a succession of two large call option trades from one investor. That helped shoot the company's shares up 6.4% by day's end, capping a Clearwire rally that over three days saw its stock price spring 20%.

This is a strong showing of confidence by the market in the survival chances for Sprint Nextel's (NYSE: S) sometimes-ignored 4G WiMAX network provider and hoped-to-be provider of future LTE services. Clearwire shares, though, are still down about two-thirds since the end of last August.

That option trader's big bet involved buying 28,000 call options for $0.15 apiece. Each option gives the buyer the right to purchase one Clearwire share for $2 before the option expires on Dec. 21.

Obviously, the investor believes that Clearwire will be selling for more than $2 a share by that date, almost doubling its current price. That's either a manifest belief in Clearwire's ability to catch up soon to Verizon (NYSE: VZ) and AT&T (NYSE: T) in the LTE build-out race, or it's buying into Clearwire's assertion of value for the wireless spectrum licenses the company owns.

Last March, Clearwire CFO Hope Cochran told an audience at a conference sponsored by Goldman Sachs that the two major carriers will eventually have to fall back on Clearwire's spectrum reserves to help them handle their huge data needs.

Of course, Cochran's hypothesis only holds water if Clearwire can manage to stay afloat until Verizon and AT&T supposedly need to come a-calling. That is no certainty: Clearwire's second quarter showed $1.2 billion in cash and equivalents on its balance sheet, enough for 12 months or so of doing business. It spent $270 million during the quarter on operating losses and interest payments.

More than one investor felt bullish about Clearwire options at the end of the week. The usual number of call and put options on any given day is 600. Friday's call option total was 32,000. Whether those are rational bets or not will take another five months to find out.

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