Allied Capital Corp., a Washington-based venture capital company whose stock is traded over the counter, reported earnings for the year ended March 31 increaded by 101 percent over the same period a year earlier.

Allied said its "net realized income" for the period was $2.6 million, up from $1.3 millin last year. Earnings per share rose from $1.14 to $1.97.

Nuclear Support Services Inc., a Woodbridge-based supplier of technical services to the troubled nuclear power industry, reported increases in revenue and net income for the six months ended March 31.

Revenues totaled $10.2 million, up from $8.98 million in the same period a year earlier, and net income rose to $445,370 from $332,821.

Fully-diluted earnings per share rose to 41 cents from 34 cents.

Input Business Machines Inc. of Frederick, Md., reported a net loss in the first quarter of 1982, despite a 39 percent increase in sales.

Input, which is traded ober the counter, said it lost $236,236, or 12 cents per share, against net income of $91,386, or 8 cents a share, in the first three months of 1981.

Sales rose from $855,646 to $1.18 million.