As a youngster growing up in Iowa City, Jim Foster received a gift from his father that many baseball-playing kids would have been excited about. It was a Pitchback -- one of those metal frames across which a net was stretched that would send thrown objects back to the thrower.

But Jim Foster, the founder and president of Arena Football, wasn't one of those baseball-playing kids. He threw footballs at the net, apparently not too bothered by the oval's odd rebounds.

"I always liked to play football more than baseball," Foster said recently. "So I threw footballs at the net and tried to figure out where they would go."

Saturday night, Arena Football makes its Capital Centre debut, when the Washington Commandos host the Denver Dynamite. Sure enough, players will be estimating how footballs will rebound off of tightly strung nets that will hang on either side of the goal posts.

Kickers, on the other hand, will be aiming their attempts at the nine-foot-wide space between the goal posts. That is, the same space at which University of Iowa kickers practiced their field goals attempts when Foster was a kid. The kicks will be drop kicks, standard field goals and kickoffs. None will be punts.

All the players will be playing offense and defense -- single platoon -- just like those tough Iowa teams in the late 1950s that Foster used to watch.

It is on a now-worn 9x12-inch envelope that these rules and ideas were scribbled one night in 1981 as Foster watched an indoor soccer game. Foster, then the promotion manager of National Football League Properties, Inc., attended an indoor soccer game at Madison Square Garden game with a co-worker and asked him if indoor soccer worked, why couldn't indoor football?

When Foster's friend asked him how he would do it, out came the envelope, which Foster still has.

"I kind of went through a mental exercise that evening," Foster said. "A lot of things came out of that night."

He envisioned a 50-yard playing field. But kickoffs would fly into the stands often, and with great expense, he thought. Thus the nets.

And what about punts hitting the ceiling? Forget punts, he thought. Everybody will just kick off. But wait -- that makes the quick kick tough. How do you replace a quick kick with a punt? The drop kick.

And what about high payrolls? Well, only eight players per team will fit on the field, anyway, he thought. For further savings, he thought the single platoon.

Working these and other ideas into the game, Foster came up with a sport that seems to be drawing interest. A crowd of 12,117 saw the Commandos play at Pittsburgh last week. Capital Centre officials are aiming for a similar crowd Saturday.

According to Commandos Coach Bob Harrison, the game's attractiveness comes stems primarily from its setup.

"People will be close to the physicalness of the game," he said. "They will be able to hear the clacking of pads and licks delivered."

The game still is not completely set in terms of rules and structure, Foster said. However, he said four things will never change about the game: single platoon, night games, no franchising and a summer schedule.

Most of these guidelines came from his original ideas and his experience with two United States Football League teams, Foster said. Although Foster said he received a contract offer from NBC after only two meetings, he shelved the arena football idea three months later, when the USFL's formation was announced.

Meantime, he took notes. A job as assistant general manager of the Arizona Wranglers and a similar one with the Chicago Blitz provided plenty to write about, he said. In the troubled league, he found "serious problems in organization," much of which came as a result of the franchising system and the bickering owners who were a strong part of it.

So when Foster, backed by his own money and that of a marketing firm in New York City, a group of investors in Chicago and a Chicago lawyer named David Sitrick, he formed Arena Sports Ventures, Unlimited -- a company that owns both the Arena Football League and its teams. When the league's four charter franchises are sold at the end of the 1987 season, they will really be sold for stock entitling the purchaser to what Sitrick calls "ownership management rights."

The price will be between $2 million and $2.5 million, yet the new owner won't have total control, Foster said. The owner won't pay salaries. The league will control the teams' budgets while the owners do just about everything else.

"An owner will have all the usual attributes of ownership, like hiring and firing, except he won't have outright ownership," Sitrick said. "We wanted to keep control of those things that didn't work out in the USFL. We want to run this as a business, not as an ego extension. It's a concept that's not unique financially, but it is unique in sports franchising."

While with the Blitz, Foster "had a hunch that the USFL was history," and heard rumblings of the move to a fall season. He soon got out, and went back to marketing.

"The USFL was spending tremendous amounts of money to compete with the NFL. It's expenses were eating it alive," he said.

But there was one thing the USFL had that Foster said he needed: the television contract. Just after he had put together enough arena football investors to end a six-month period of "living on credit cards," Foster signed a contract with ESPN. For the first season, the contract calls for the broadcasting of five games, with ESPN charging no production fees and allowing the league to keep all advertising revenue. In following seasons, the league and ESPN will split all revenues and costs.

"I don't believe you can be a major league without a TV contract," said Foster, who added that he wouldn't have gone through with the league without a contract. "It brings in revenue, exposure and credibility -- a lot more than just money."

Foster said the contract with ESPN was especially attractive because the network was primarily interested in night games. Day games, he said, didn't work too well for the USFL during the summer.

"People are creatures of habit," Foster said. "When it's nice out during the weekend, they're going to go the beach or something like that. We're going up against movies, bowling and discos."

To find cities for the league, Foster looked at both facility availability and market potential. He said Washington was chosen for its market, but Chicago was chosen because successful exhibition games had been played near there. Denver beat out Los Angeles for a team because of high interest in that city and low arena availability in southern California. Pittsburgh won a team over several Southeastern cities for similar reasons.

Assuming the league stays alive, Foster says it will put at least four more teams on its map next season. He said cities in the Midwest, Florida, Texas and California are being considered, as well as Oklahoma City and New York City.

"This is his {Foster's} vision," Sitrick said. "It would be hard to be happy if you have a dream like that and weren't able to try it."