The Federal Reserve Board, signaling its determination to raise interest rates and curb inflation, Friday hiked the rate it charges commercial banks from 6.5 percent to 7 percent, the highest level since March 1986. The discount rate has been 6.5 percent since Aug. 9, 1988. The news sent the value of the dollar soaring and raised fears that the trade deficit would suffer because U.S. goods would lose the competitive edge in world markets they gained with the falling dollar. The Fed's move followed by a day an increase in the prime lending rate - the rate banks charge their best corportate customers - to 11.5 percent. Chase Manhattan Bank and Republic National Bank of New York announced the half-percentage-point increases on Thursday, and other banks followed Friday.