Despite a strong fourth quarter, Woodward & Lothrop reported yesterday that its fiscal 1980 earnings dropped 3.6 percent to $9.645 million ($3.95 per share) from $10.01 million ($4.10) a year earlier.

Woodies Chairman Edwin K. Hoffman said that 1980 "was not a banner year for the department store industry or for Woodward & Lothrop," adding that the Washington retail company does not anticipate "any appreciable sales increase until the third and fourth quarter of 1981."

Among factors adversely affecting earnings, Hoffman cited high interest rates, inflation, high inventory shortages and expenses related to the opening of a new store at Fair Oaks. In addition, "presidential election years invariably are somewhat difficult here in the nation's capital," he added.

Sales for the fiscal year ended Jan. 31 rose 4 l/2 percent to $308.37 million from $295.181 million.

Fourth-quarter net earnings jumped 16 percent to $5.946 million ($2.46) from $5.124 million ($2.10) for the comparable quarter a year ago. Sales in the quarter increased 6.4 percent to $101.205 million from $95.099 million.

While noting the fourth-quarter sales improvement, Hoffman said that results for the year were "severely hampered" by the effects of the economy on consumer spending.

Hoffman said, however, that the company benefitted from a higher investment tax credit, which resulted in a reduced effective tax rate of 43.3 percent for 1980 compared with a rate of 47 percent in 1979. The lower tax rate increased per-share earnings by 26 cents for the year and 11 cents for the fourth quarter, he said.

Microdyne Corp. reported an increase in both sales and earnings for the first quarter ended Feb. 1. Microdyne is a supplier of satelite television products and telemetry equipment with facilities in Rockville and Cumberland, Md.

Sales for the quarter rose 35 percent from $5.279 million a year ago to $7.132 million, while net income increased 31 percent from $794,852 to $1.044 million.