UNC Resources Inc., which has tried to retrench in recent years and to diversify away from its uranium-production origins, lost $14.1 million last year, half of that in the final quarter.

UNC's loss compares with earnings of $6.9 million (65 cents a share) during 1981. Revenue in 1982 increased 28 percent to a record $354 million compared with $277 million the year before.

For the fourth quarter, UNC lost $7 million compared with a loss of $1.1 million the year before. Quarterly revenue grew to $84 million from $66 million in 1981.

UNC, based in Falls Church, is a diversified resources and manufacturing company involved in minerals, nuclear components, machine tools, ship repair and construction, and services to the oil and gas industry.

In explaining the company's performance for 1982, Chairman Keith A. Cunningham said yesterday the year should be considered "further . . . transition, in which considerable progress was made in restructuring UNC and broadening its business base to offset the current decline in the uranium market."

However, Cunningham said the uranium operations had been "profitable since suspending production in midyear to deliver purchased uranium under our contracts."

He said losses could be attributed to contract terminations in the ship-repair subsidiary and a weak market for offshore-oil-service vessels. Another subsidiary, National Automatic Tool Co., had greater losses in the fourth quarter, but orders have increased since then. HGIC Corp., the parent company of Home Guaranty Insurance based in Richmond, lost $1,985 in 1982, compared with net earnings of $313,480 (19 cents a share) in 1981. Income from premiums and investments amounted to $1.99 million in 1982 compared with $2.11 million in 1981. Evaluation Research Corp. of Vienna had earnings of $516,000 (44 cents a share) during 1982 compared with $361,000 (32 cents) in 1981. Revenues of the professional and technical services firm increased to $17.3 million last year from $13 million in 1981.

ERC, which went public in December, concentrates on engineering, logistics, information sciences and energy and environmental analysis. Preston Trucking Co. Inc. reported that profits declined 17.9 percent last year to $5.1 million ($1.64 a share) from $6.3 million ($2) in 1981, while revenues increased to $222.3 million from $197.6 million.

Fourth-quarter earnings dropped 33 percent to $1.4 million (45 cents) from $2.1 million (67 cents), while revenues grew to $57.2 million from $50.9 million.