Hechinger Co. yesterday announced record profits for the second quarter of its fiscal year and the highest sales for any quarter in the hardware store chain's history.

For the quarter ending Aug. 1, the company reported profits of $2.2 million (30 cents a share), a 26 percent increase over fiscal 1980 second-quarter profits of $1.7 million (27 cents). Sales for the quarter rose 29 percent to $57.7 million from $44.8 million.

Profits for the first half of the Landover-based chain's fiscal year rose to $4.0 million (54 cents) from $3.0 million (46 cents) as sales rose from $85.6 million to $109.6 million.

The per-share figures reflect a 3-for-2 stock split that was effective May 22.

And Radiation Systems Inc. has announced a 41 percent increase in fiscal 1981 profits to $1.1 million (84 cents a share) from $836,000 (71 cents). Sales for the year, which ended June 30, rose to $9.8 million from $7.6 million.

The Sterling, Va., antenna products company also reported a sharp rise in fourth-quarter profits to $491,000 (30 cents) from $262,000 (22 cents). Sales for the quarter rose from $3 million in 1980 to $3.1 million.