SAN FRANCISCO -- Sirf Tech ( SIRF) posted a wider loss in the third quarter, as sales at the chipmaker fell sharply. The San Jose, Calif., company said revenue in the three months ended Sept. 27 decreased 34% sequentially and 67% year-over-year to $60.1 million. Sirf said sales were affected by continued competitive pressures as well as weakness in demand because of the global economic uncertainty. The company posted a loss of $20.9 million, or 34 cents a share, vs. a loss of $16.1 million, or 28 cents a share at this time last year. The company's gross profit margin declined to 42.7% compared with 49.3% in the year-ago period, and some of Sirf's operating expenses actually increased slightly during the quarter, even as sales plummeted. Shares of Sirf fell 5%, or 5 cents, to 90 cents in extended trading Wednesday, down dramatically from the 52-week high of $30.61. Once a leading maker of the GPS chips used in personal navigation devices, Sirf has fallen upon tough times as new players such as Broadcom ( BRCM) and Qualcomm ( QCOM) have entered the market and driven down prices for its chips. Meanwhile, the market for the personal navigation devices that use GPS chips is under pressure. On Tuesday, Garmin ( GRMN), the world's No.1 maker of PNDs said that sales in the fourth quarter will be about $300 million less than it previously expected. Sirf didn't immediately provide a specific financial forecast Wednesday other than to say that its new products are showing good "design win traction," but that the company continues to be cautious in its outlook due to challenging competitive and economic conditions. The company is scheduled to hold a conference call with analysts Wednesday.