U.S. factory use rose in February for the first time in seven months, reaching a rate of 71.8 percent of capacity, the Federal Reserve Board reported yesterday.

The new report also revised January's factory use to 70.6 percent of capacity from the 70.4 percent reported last month.

The news was basically in line with the board's report on Tuesday that industrial production rose in February by 1.6 percent for U.S. industry as a whole and by 1.8 percent for manufacturing.

Analysts noted that bad January weather apparently had held down both production and factory use, and they cautioned that the February improvement therefore might seem more robust than it actually was.

So no one was predicting any sudden slowing of unemployment, with companies calling laid-off workers back to their factories. Still, the utilization rate did rise after six monthly declines, a development sure to stir new hope that the recession might be nearing an end.

Capacity utilization improved by 1.2 percentage points for both manufacturers and producers of industrial materials. The utilization rate for production of motor vehicles and parts rose for the first time in several months but remained under 50 percent, the report said.

"Operating rates also increased substantially for producers of textiles, and more moderately for producers of paper, chemicals, rubber and plastics, fabricated metals, nonelectric equipment, instruments and stone, clay and glass products."

On the negative side, "Production in the primary-metals industry continued to weaken in February as operating rates declined for producers of iron and steel and of nonferrous metals."

Meanwhile, the F.W. Dodge division of McGraw-Hill reported that construction of new homes fell 16 percent to 1.12 million units last year from 1.33 million in 1980 and 42 percent in the final quarter to 213,197 from 370,107 in the last three months of 1980.

And in Atlanta yesterday, President Reagan's top economic adviser delivered what appeared to be an apology for the failure of the administration's economic program to fulfill earlier promises.

Murray Weidenbaum, chief of the president's Council of Economic Advisers, told a conference on Supply Side Economics in the 1980s that, although it is too early to evaluate Reaganomics, "Surely it is apparent that great difficulties face any administration attempting to develop and carry out bold and comprehensive new programs."