Businesses are sampling a hot new dish -- not a gourmet meal but a compact new satellite dish that offers appetizing savings by letting companies communicate between branches without using the telephone system.

An example of one more form of "bypass" technology assaulting the telephone industry, the new 4- to 6-foot-wide satellite dishes, which are easily mounted on roofs, threaten to deflect billions of dollars a year in what businesses now pay phone companies for data transmission, according to analysts.

While the dishes are mainly for data needs, they can also transmit telephone conversations.

"These dishes right now have the capability to replace $3 billion worth of data transmission service yearly provided by both local and long-distance telephone companies, primarily American Telephone & Telegraph Co.," said Jerome Lucas, president of TeleStrategies Inc., a McLean telecommunications consulting firm.

"The phone company is the best phone company on earth," said John Tilley, assistant vice president for business development for M/A-Com Inc., which manufactures the dishes at its Germantown, Md., facility. "It was designed for telephone service but it was not designed for data, and more and more businesses must have data communications to survive."

Currently, the telephone companies principally provide lower-speed data transmission and cannot always supply customers with all the data-transmission lines they need.

Outages also make life difficult for companies that need a reliable way to communicate, analysts say.

In terms of revenues, the dishes represent "a multibillion-dollar market in about four years," said Lucas. "You'll see about a million of these two-way communications dishes by the mid-1990s."

The driving force behind the new dishes is the breakup of the Bell System, which has left telecommunications managers grappling with with different vendors and escalating costs, said Lucas.

The new dishes, costing between $6,000 and $16,000, give companies flexibility when they want to expand the system and offer a cheap way to keep down costs.

"It lets us manage our communications functions without having to deal with several different phone companies," said David Karney, vice president of management information service for the Southland Corp., based in Dallas.

"It lets us expand our network on an incremental and cost effective basis."

Southland has just purchased $6 million worth of the dishes from M/A-Com Inc., a diversified digital telecommunications manufacturer based in Burlington, Mass., whose satellite dish division is located in Germantown.

The dishes will be placed at 300 local business offices across the country that manage 7,500 7-Eleven stores and be used for accounting, payroll and personnel functions as well as phone calling starting in early 1987.

The dishes are expected to save the company nearly two-thirds of its annual $1.5 million bill from phone companies for data transmission, Karney said.

In fact, M/A-Com Inc. is soliciting business among the top Fortune 500, and M/A-Com officials said they already have found considerable interest in the service.

Another customer is Wal -- Mart Stores, which signed a $16 million contract with M/A-Com.

Wal-Mart will install the dishes in 750 stores and start service in 1987, using the dishes for voice and data needs as well as videoconferencing.

"We're a company that's very big on communicating with our people," said Bob Martin, a Wal-Mart spokesman.

Apart from using the dishes to hold videoconferences and to track inventory, pricing uniformity and payroll information, the dishes will cut the $10 million annual phone bill, part of which goes to phone companies for lines leased to transmit data, he said.

"We're really in small town America, and we have a lot of different vendors to deal with and that's a real management problem -- just simple coordination between multiple telephone companies is difficult to manage and we hope to make it easier," he said.

Another advantage is that companies relocating take the equipment with them. "All the equipment is transportable," he said.

The first two contracts M/A-Com has won represent more than 1,000 dishes, and the company is expanding its manufacturing facilities and gearing up to provide 200 to 300 dishes a month within the next two years.

Customers using the dishes also will need to lease capacity on satellites used to relay signals from one location to another, but M/A-Com will help the companies arrange that portion of the service, Tilley said.

As retailers and other companies catch onto the advantages of dishes, competition will intensify in still another area of the telecommunications business, said Tilley.

"There is going to be competition -- it's very difficult competition," said Tilley. While 13-year-old M/A-Com has been developing the technology for a number of years, "There are some genius small companies that can give everybody a run for their money," he said.

There are companies already working on giving M/A-Com competition, and some are not so small. They include the Harris Corp., in Melbourne, Fla.; Equatorial Communications Co. in Mountain View, Calif.; Vitalink Communications Corp., also in Mountain View, and others, said TeleStrategies' Lucas.

Right now several vendors, including Communications Satellite Corp. are competing to win a contract to provide satellite dishes for two-way communications to Federal Express Co. for its Zap Mail facsimile transmission service.

Other major corporations are seeking to use the service and competitors for the market are sure to follow.