Financial General Bankshares Inc.'s income before securities transactions increased 30 percent to a record $13.49 million ($2.04 a share) last year from $10.36 million ($1.58) in 1977, the Washington bank holding company reported yesterday.

Financial General President J. William Middendorf II said more loans, higher interest rates and consolidation of two groups of subsidiaries were the major factors aiding profits.

Net income after securities losses was $13.4 million ($2.03) up 25.8 percent from the $10.65 million ($1.63) earned in 1977.

For the fourth quarter, Financial General earned $3.9 million (59 cents), 40 percent more than the $2.78 million (43 cents) earned in the same period in 1977. Net for the quarter was $3.88 million (59 cents), up 30 percent from $2.98 million (46 cents) a year earlier.

Middendorf said interest income for the year was up 17.5 percent as a result of loan growth and higher interest rates, with total loans at year-end of $1.16 billion. Yearend deposits were $1.84 million, up 4.8 percent, and total assets were $2.1 billion.

Early in the year, FG merged three subsidiaries into First American Bank of Virginia, and at year-end it created First American Bank of Maryland by combining two other banks.

Communications Satellite Corp. reported 1978 net profits of $34.24 million ($4.28 a share), up 5.4 percent from the $32.5 million ($3.27) earned in 1977.

Operating revenues for Comsat increased about 9 percent to $184 million from $168.2 million because of higher revenues from the company's three satellite systems, Intelsat, Marisat and Comstar.

The Washington firm said operating expenses last year were up $14.8 million to $155.4 million, due moslly to the expense of launching three additional satellites.

Reporting operating income of $29.2 million -- up from $27.6 million -- Comsat said its share of the losses of the new Satellite Business System increased to $3.4 million from $2.7 million. SBS. a joint venture of Comsat's Comsat General subsidiary, Aetna Life & Casualty and IBM, is a planned domestic communications satellite system that is not yet in operation.

For the fourth quarter, ended Dec. 31, Comsat's net income increased to $10.6 million from $7.65 million.

Profits of Pargas Inc. rose in the final quarter but were depressed for the full year because of coal mining losses, the Waldorf-based company reported.

In the three months ended Dec. 31, Pargas earned $2.6 million (71 cents a share) compared with $2.3 million (62 cents) a year earlier, a gain of 15 percent. Revenues were about $40 million for both periods.

Chairman William C. Hill said coal operations reduced the latest quarter's profits by about 19 cents a share.

For all of 1978, Pargas earnings slipped "materially below those of the prior year due solely to the losses incurred in coal mining," Hill stated. Profits were $4.2 million ($1.12) compared with $7.2 million ($1.93), as sales rose to $148 million from $137 million.

Earnings from Pargas's principal business -- distribution of liquefied petroleum gas, or propane -- were $2.21 a share in 1978, higher than overall profits of Pargas in any prior year. Coal losses of about $1.09 a share offset these earnings.

Hill said the coal losses reflected inventory and operating difficulties. Sufficient production and accounting controls have been installed to prevent a recurrence of big inventory losses, he added.

Directors voted to increase the Pargas quarterly dividend rate to 27 cents a share, payable March 1 to owners of record Feb. 15, for an annual rate of $1.08 compared to $1.06 in 1978. Pargas has increased its common payout rate every year since the firm went public in 1961.

Student Loan Marketing Association reported 1978 earnings of $5.9 million compared with $4.3 million the previous year. Per-share earnings increased to $35.43 from $26.09, and total assets rose to $967 million from $556 million.

Known as Sallie Mae, the firm was created by Congress in 1972 to provide a secondary market for guaranteed student loans. To date, Sallie Mae has provided some $1.2 billion to lenders through advances, loan purchases and commitments to buy loans.

Directors voted a quarterly dividend of $1 a share payable March 15 to owners of record Feb. 15. Stock-holders are primarily educational and financial institutions engaged in the student loan program.

Richmond, Fredericksburg & Potomac Railroad reported record earnings in 1978 of $10.6 million ($29.58 a share). Total net income in 1977 was at about the same level ($29.48 a share) but had included one-time gains including property sales equal to $3.94 a share. Revenues rose 7 percent to $37.8 million, reflecting mainly a 5 percent gain in freight tonnage.

National Bank of Fairfax reported 1978 profits of $1.8 million ($5.33 a share) compared with $1.3 million ($3.86) in 1977. Directors of the bank, with assets of $23 million, voted a dividend of 65 cents a share that was paid Dec. 31 to owners of record last Dec. 15.

New Virginia Bancorp. of Spring-field reported 1978 earnings of $1.7 million ($1.31 a share) compared with $1.4 million ($1.05) the previous year, a gain of 24 percent. Assets rose 11 percent to $180 million, and deposits increased 7 percent to $159 million. The bank firm recently acquired First City Bank of Newport News.