Communications Satellite Corp. yesterday announced second-quarter 1985 earnings of $16.2 million (89 cents a share), an increase of $4.5 million (24 cents) over the same quarter last year. The international telecommunications firm reported revenue of $130.2 million, compared with $107 million for the same period in 1984.

Comsat said last year's second-quarter results reflected heavy losses from its partnership interest in Satellite Business Systems, a business telecommunications company. Comsat sold its interest in SBS last July to its partners, Aetna Life & Casualty Co. and International Business Machines Corp., after sustaining a $100 million loss. In this year's second quarter, Comsat said it wrote off $1.7 million worth of defective inventory.

For the first six months of 1985, Comsat said it earned $32.1 million ($1.77) on revenue of $252.1 million. In the same period last year, the Washington-based company reported earnings of $24 million ($1.33) on revenue of $212.1 million.

* Richmond-based Robertshaw Controls Co. reported a second-quarter income of $7 million ($1.27 a share) on sales of $103.8 million. For the same quarter last year, the company netted $6 million ($1.11) on revenue of $104.9 million.

The second-quarter 1985 earnings included a one-time gain from the sale of a manufacturing plant in Anaheim, Calif. While Robertshaw sold the plant for more than $4 million, according to a company spokesman, it reported a net gain from the sale of only $1.1 million after closing costs.

The company, which manufactures automatic controls for aircrafts, cars, commercial buildings and home appliances, earned $13 million ($2.39) on sales of $208 million for the first half of this year, down a penny per share from the first quarter in 1984, in which Robertshaw had sales of $212.2 million.

* Gray and Co., the Washington public relations and lobbying firm, yesterday reported a 74 percent jump in revenue to $6.1 million during the three months ending May 31 from $3.5 million during the same period last year. The growth in revenue also represented a 17 percent increase over the previous quarter.

The company also reported a more modest increase in profits, from $318,590 to $292,504, for the three-month period, which is the first quarter in its fiscal year. Earnings per share remained at 13 cents.

A Gray spokesman said the substantial increase in revenue reflects the company's purchase last year of Strayton Corp., a Waltham, Mass.-based computer firm, and a growth in the number of clients, including a new $10,000-a-month contract to represent the Saudi Arabian government.

* Maryland National Corp., the holding corporation for Maryland National Bank, has reported a 41 percent increase in profits during the second quarter.

Maryland National said that second-quarter net income was $17.6 million (96 cents a share), compared with $12.5 million (77 cents) for the same quarter of 1984.

Profits for the first half of 1985, meanwhile, were up 44 percent from the same period last year. Net income for the first half amounted to $33.6 million ($1.95), compared with $23.3 million ($1.43) earned during the first half of 1984.

Chairman Alan P. Hoblitzell Jr. said that the growth of commercial and retail loan portfolios, relatively high net interest margins and increases in noninterest revenue contributed to Maryland National's higher earnings.

He said the bank's reserve for possible credit losses increased to $75.3 million, or 1.37 percent of total loans, at the end of the quarter from 1.28 percent on March 31 and 1.12 percent on June 30, 1984. According to bank officials, the increase was the result of the "continued strong growth in loan volume and management's desire to maintain a prudent ratio of reserves against its expanding loan portfolios."

Maryland National reported assets of $7.3 billion as of June 30, up 16 percent over the second quarter of 1984.

* First American Bank of Maryland has reported a 12.6 percent increase in second-quarter profits to $1.0 million ($1.09 a share) from $961,000 (97 cents) for the second quarter of 1984. Six-month profits rose to $2.1 million ($2.16) from $1.8 million ($1.83) for the same period a year ago. The bank's assets totaled $575.4 million as of June 30, up 25.5 percent from a year earlier.

* First American Bank of Virginia has reported an 11.6 percent increase in second-quarter profits to $4.8 million ($1.02 a share) from $4.3 million (92 cents) in the second quarter of 1984. Six-month earnings rose to $9.4 million ($2.00) from $8.6 million ($1.82) in the same period of 1984. The bank's assets were $2.195 billion, up 20 percent from $1.829 billion as of June 30, 1984.