PHH Group Inc., a Hunt Valley firm that manages vehicle fleets and assists firms with personnel relocations, posted a 20 percent increase in earnings for the nine months ended Jan. 31, Chairman Jerome W. Geckle said yesterday.

PHH posted record profits of $22.3 million ($1.45 a share) on revenues of $338.5 million for the three quarters compared with $16.4 million ($1.21) on revenues of $287.2 million last year.

For the latest quarter, PHH made $7.5 million (49 cents) on revenues of $111 million, compared with $6.3 million (43 cents) on revenues of $93.6 million in 1981.

Geckle said the increases were in line with the companies' objectives. The results are gratifying, he said, "in view of the current recession and the resulting adverse effects on the housing market and the automotive industry generally."

A Washington-based, small-business investment firm, Greater Washington Investors Inc., reported a 4.2 percent increase in its net asset value for the year ended Dec. 31, to $4.8 million ($2.65 a share) from $4.6 million ($2.54) for 1980.

Tech Serv Inc., a Beltsville-based electronic controls and target systems manufacturer, said that for the six months ended Dec. 26, 1981, it had profits of $70,228 (12 cents a share) on sales of $1.4 million. For the same period of 1980, profits were $18,815 (3 cents) on sales of $1.2 million.

For the latest quarter, Tech Serv posted earnings of $133,305 (23 cents) on sales of $916,172, compared with a $37,373 loss on sales of $488,685 during 1980.