When the second session of Congress opens today, many downtown lobbyists will receive for the first time live gavel-to-gavel television coverage from the House.

Until now, the District hasn't been able to receive live House coverage at a reasonable price. Since the House began televising its proceedings in 1978, only cable television stations have routinely received the broadcast. There is no cable station in the District to deliver the service.

But George Mason University Foundation, Inc., has ended the blackout. The nonprofit organization set up an educational microwave television station to broadcast House proceedings into the District. Subscribers pay $495 a year for what George Mason calls its "Capitol Connection." At the same time, the university helps cover the cost of broadcast facilities it hopes to use for its own students.

The new service is something private and government lobbyists have wanted for a long time.

Without television service, lobbyists have problems following House proceedings. They have to station someone in the gallery waiting for the debate that concerns them, and the aide is not allowed to take notes there. If a client wants immediate reports, periodic trips have to be made to a telephone booth at the risk of missing something.

Even the White House feels the constraints. According to a former aide to President Carter, it was frustrating to know that a housewife in Kansas City watching the cable station could have more up-to-date information than the president's men in the White House during a crucial debate.

Joan Teague, director of the House broadcasting system, said the House wanted to avoid favoring anyone with a special hookup. "We said if we let one person, we'd have to let everybody in town," she recounted.

The alternative was to arrange for a telephone hookup into the House television mixer box in the Capitol complex. Special cable is needed to transmit a picture. A government agency within a mile of the Capitol was told by the Chesapeake and Potomac Telephone Co. that the cost would be in the tens of thousands of dollars for the telephone connection and several hundred dollars a month to maintain the link.

Last summer a key House member suggested that the House set up its own low-power television station to satisfy the demand within Washington. Rep. Charlie Rose (D-N.C.), chairman of the House Administration subcommittee that oversees the workings of the television system, said, "We're getting an increasing number of requests for our signal from all over town."

Rose's comment was the spark for Michael Kelley, a George Mason University English professor who is responsible for the university's telecommunications efforts.

The university already had permission to use some transmission facilities of Artec, the local cable television company. The institution had expected to seek an instructional microwave license from the Federal Communications Commission as a teaching aid for its nursing and law schools. Kelley said selling a linkup to live House coverage could help pay for the facility the university wanted.

So Kelley applied for a license last fall for four channels--one for the House, one in anticipation of the Senate's approving television for its chamber, and two forteleconferences and seminars. Later, he sought and won four "repeater" channels that can be used to boost power, or for separate programming.

With the extra channels, Kelley plans live broadcasts from regulatory commission meetings. "It's possible, it's do-able and it will be done this year," he said.

Now that the service is available, even Ma Bell wants it. The legislative offices of American Telephone & Telegraph Co. are signed up to get the service.

The Republican National Committee, which is only a block from the Capitol, is subscribing. And Kelley said the White House is seriously exploring buying the link.

Lobbyists are excited by the prospect of having the live debates. Gary Hymel, formerly an aide to Speaker Tip O'Neill (D-Mass.) and now a lobbyist with Gray & Co., said, "I can't imagine any corporation or law firm or lobbying firm that wouldn't have it."

"Everything is timing in this business. Knowing first, knowing ahead, knowing when it happens," Hymel said. "It seems to me it'd be worth it if you use it once a year."

According to a Commerce Department lobbyist, live TV coverage is, in some ways, better than being there. "They always flash the name of whoever is there speaking on the floor," said Paul Vander Myde, a Commerce assistant secretary for congressional affairs. Lobbyists can keep better track with televised proceedings because they can take notes, he adds.

Of course, it also is a time saver. "Rather than park somebody up in the gallery for a whole day, we can just kind of keep an eye on what's happening on the floor," Vander Myde said.

The Capitol Connection went on the air Dec. 16, the last day of the first session of this Congress. According to George Mason's Kelley, the idea was to work the bugs out of the system. During the recess, the station broadcast the Cable Satellite Public Affairs Network (C-SPAN) programming on one channel, with the other three channels unused.

C-SPAN is the nonprofit company that delivers the live House signal outside of Washington. When there is no live House action to broadcast, C-SPAN offers both taped and live congressional hearings, and a variety of other programs, including National Press Club luncheons and International Trade Commission hearings.

In theory, there will be some places in the District which will not be able to receive the service. Geroge Mason uses a microwave distribution system that requires line of sight reception. In practice, however, Kelley has found that there are ways around the need to "see" the transmitter. In one instance, a subscriber was able to get the signal as it ricocheted off a neighboring building.

Subscribers need a small, two-foot antenna with a crystal receiver, or "down converter," on it. The antenna is a rod with small, evenly spaced metal discs on it.

The user picks up the House on Channel 8 of a normal television set. Other programming will go on Channels 10 and 12 and one called "13 prime."

Orders were slow in the beginning, but have picked up following some mid-January publicity. Kelley said last week that 11 orders have been placed, 12 are in process, and 20 other potential customers have made inquiries.

The Capitol Connection may face some competition from another nonprofit broadcasting organization soon. Central Virginia Educational Broadcasting plans to transmit live House proceedings free on Channel 56. A transmitter is under construction in Virginia that CVEB hopes will equal Channel 26 for local broadcast reception quality, according to Dan Ward, vice president and general manager of the station. CVEB hopes to have Channel 56 on the air by fall.

The group now broadcasts the House on Channel 53, but the proceedings are often delayed broadcasts.

Some say the Capitol Connection will easily be able to compete against such a free service. If the Senate allows live television coverage, the Capitol Connection will simultaneously broadcast the House and Senate, which Channel 56 isn't prepared to offer.

Does simultaneous coverage make the Capitol Connection worth the price? "It does to us, absolutely," said David Muller, project director of the Republican National Committee's campaign planning and development branch.

The other potential competition is a District cable television franchise that would offer C-SPAN coverage. But such a franchise is at best several years away.

Even then, "there will always be a need for this service, particularly in a town like Washington," said Brian Lamb, president of C-SPAN, because cable systems are unlikely to hook up offices downtown.

The university's hope is to make use of all channels, including Channel 8 when the House is in recess, to expand the presence and local influence of George Mason. As downtown offices subscribe to the Capitol Connection, "they are going to have an electronic-television connection to a major state university," Kelley explained, "and the opportunity to take extended courses in the law," as well as in economics, political science, and nursing.

He adds, "we can do certain kinds of informational seminars and teleconferencing into federal agencies."

The institution has set up a satellite earth-receiving dish, further expanding the kind of programming it can deliver over its station. Kelley plans a Capitol Connection hookup with major theaters in the area, including the Kennedy Center, which will enable George Mason to offer many satellite services to large audiences. For example, Kelley said, a satellite could link several distant locations for a conference, or for educational presentations.