Radiation Systems Inc., a McLean antenna manufacturer, has reported lower sales and profits during the year ended June 30.

Earnings totaled $434,000 (61 cents a share) compared with $573,000 (74 cents) a year earlier as revenues dipped to $3.5 million from $5.1 million.

President Richard Thomas said that while the firm is not pleased with the lower sales, "it took pride in having maintained an excellent profit." The primary reason for reduced volume was a delay in booking anticipated orders for several new products. But a $3.5 million order for 112 transportable military antennae in June was a major breakthrough, Thomas added.

The RSI president forecast that a surge of orders for new military and commercial products will result in record sales and profitability.RSI is expanding its international and domestic sales operations and plans a "major initiative" in the fixed satellite earth station market.

Baltimore Gas Electric Co., in a monthly statement, reported a continued recovery from depressed profits in 1977. Earnings for the first eight months of 1978 were $89 million ($2.51 a share) compared with $74 million ($2.10) in the 1977 period as sales rose to $648 million from $530 million.