Hechinger Co., whose newspaper advertising sections are as much a part of Sunday papers as the comics, will start its first major radio ad campaign this fall, executives disclosed yesterday.

The radio commercials will be broadcast only outside the Washington area in an effort to boost the home improvement chain's image in new markets where it is less well known, said President John W. Hechinger.

"We're already a household word in Washington, but not in these other places," Hechinger said in an interview after the company's annual stockholders' meeting at which the radio campaign was previewed.

The broadcast advertising will be targeted at Baltimore, Richmond, Tidewater Virginia and parts of Pennsylvania, where the chain has opened new stores and where newspaper readership is not as high as in Washington, explained Hechinger Chairman Richard England.

Radio commercials will be in addition to the 2 million newspaper supplements distributed each week which already make Hechinger's ad budget twice as big as the average for the home-improvement business.

The extra advertising is meant to increase the company's share of the outlying markets, Hechinger said. Stores in the Norfolk-Newport News area already exceed the sales of comparable units in the more concentrated Washington market, but they are not maximizing the potential business in the market.

The Washington-based home-improvement chain, one of the 10 largest in that business, has no plans to enter new market areas, company officials said. The first two of a planned 15 stores in the Philadelphia area have opened, a third will be built be next spring, and the next dozen will provide the chain's immediate growth.

England said the do-it-yourself business is proving "recession resistant," and Hechinger said all the company's stores operated profitably in April, including the newest ones. "Every store that had been open 60 days was in the back, including the writeoff of opening expenses and headquarters overhead," he added.

With sales up 27 percent in the first quarter, Hechinger has bought land next to its three-year-old headquarters in Landover for possible expansion and has hired materials-handling experts to study how many additional stores the headquarters warehouse can supply. Hechinger said.

The $1.5 million in inventory needed for each new store is being financed from current cash, and other growth costs are being paid from last year's sale of stock, said Stephen Bachand, senior vice president for finance and administration.