Dynalectron Corp. of Mclean reported a sharp increase in third-quarter income, attributing the gain primarily to improvement in its electrical contracting and technical-services businesses.

Net income for the quarter was $3.68 million (43 cents a share) compared with $610,000 (8 cents) in the comparable period a year ago. Revenues increased from $114.3 million to $118.7 million.

Dynalectron also attributed its third-quarter results to higher net interest income and return of its environmental group to profitability.

Nine-month net income was substantially higher than in the prior year at $9 million ($1.06) compared with $2.4 million (33 cents). Revenue increased from $317.5 million to $349.2 million.

Bank of Virginia also reported higher earnings for both the third- quarter and nine-month periods.

Net income for the quarter totaled $3.9 million (66 cents a share) compared with $3.9 million (64 cents) in last year's third quarter.

Nine-month net income increased from $9.69 million ($1.68) to $9.9 million ($1.68).

Frederick Deane Jr., Bank of Virginia's chairman, said the third-quarter results represent a continuing improvement in net interest income. Credit card and variable-rate mortgage fees also contributed significantly to earnings.

Norfolk & Western Railway had third-quarter net income of $92.7 million ($2.85 a share) compared with $43.6 million ($1.38) in the prior year. Revenues rose from $375.8 million to $506.1 million.

Net income for the first nine months was $197.5 million ($6.08) compared with $151 million ($4.81) in the comparable period a year ago.