Celeritek

(CLTK)

lowered its third-quarter revenue estimate because of a decision by

Motorola

(MOT)

, one of its major customers, to stop using a dual-sourced power amplifiers in its cell phones.

Recently, shares were down 28%, or $2.03, to $5.10, in premarket trading, according to Instinet.

The company now expects revenue to be $10 million to $11 million in the quarter, with Motorola accounting for 25% to 30% of that figure, and down from its original expectation of $13 million to $14 million.

Analysts polled by FirstCall/Thomson Financial expect the company to lose 20 cents a share, on revenue $13.7 million in the quarter. In the third quarter of 2002, the company lost 8 cents a share, on revenue of $14.7 million. Motorola accounted for 43% of total 2002 revenue.

Celeritek said it expects Motorola's decision to affect fourth-quarter results more than the third quarter's.

Santa Clara, Calif.-based Celeritek provides semiconductors and power amplifiers. Shares closed at $7.04 Friday on the

Nasdaq

.