Losses by a subsidiary caused Scope Inc., a diversified electronics and research firm, to post a loss for 1981, company officials said yesterday.

Reston-based Scope lost $1.8 million ($1.49 a share) on sales of $73.6 million during 1981. The firm decided to discontinue certain product lines of MRC Corp. of Hunt Valley, Md., accounting for the 1981 loss, officials said. From continuing operations, Scope reported income of $186,915 for the year. That compares with net income of $2.5 million ($2.06) on sales of $70.7 million for 1980.

During the fourth quarter of 1981, Scope had net income of $760,542 (62 cents) from continuing operations, and $421,949 after providing reserves for the discontinued operations, compared with earnings of $846,775 in the final quarter of 1980. Sales were $20.1 million for the fourth quarter, compared with $19.1 million in the last quarter of 1980.

Scope officials said yesterday that the annual meeting will be delayed several months from its customary April date to allow time for the proxy to be reviewed regarding the company's spinoffs of two subsidiaries.

Officials also voted to pay 15 cents a share dividend on May 6 to to stockholders of record of April16.