Gil Thompson, president of the Cairo condominium association in Northwest Washington, has anxiously eyed the satellite-receiving dishes popping up on buildings around town. He resisted lobbying for a dish for the Cairo, preferring to wait for the District to get cable television.

But Thompson's mood changed recently when the city's cable firm asked to modify its franchise agreement and raised some doubts about when construction would begin. Suddenly, a satellite dish began to look more attractive.

"Now I think it might be years before we get cable, if we ever get cable," said Thompson, who lives in the 169-unit Q Street building. "The Cairo condominium must begin to consider alternatives to waiting an indefinite time."

Another D.C. resident, Edward J. Doheny of Northwest, suggested that the council reject the modifications and reopen the cable bidding process even though it will "increase my level of frustration as my suburban friends continue to enjoy their cable systems."

Thompson and Doheny are among only a few dozen District residents who bothered to write, telephone or advise the City Council on the proposed concessions to the cable developer. There are 250,000 potential cable TV subscribers in the city.

Despite the meager citizen reaction, council members last week approved a number of concessions to District Cablevision Inc. to help the firm raise enough money to build the cable television system, but rejected provisions that might have freed the company from having to serve the entire city.

Council members indicated that they felt they already had a mandate from their constituents to get the city a cable system as soon as possible.

The resolution adopted by the council read in part that it is "in the interest of the residents . . . to have access to cable television service at the earliest possible date," and the council granted major modifications in its cable-franchise agreement in an effort to speed up the construction schedule.

"People really care about cable," said City Council member Frank A. Smith Jr. (D-Ward 1), "and their concern is expressed in a longing for cable. They don't lobby for this company or that company and they don't get involved in protesting council action on modifications."

Council member Nadine P. Winter (D-Ward 6) interpreted the lack of response differently. "I've not heard from any constituents supporting the concessions. A lot of people have gotten disgusted."

Most of the people who testified at council public hearings on the modifications have been District Cablevision supporters or investors rather than potential cable subscribers.

The council, seeking to salvage the troubled cable franchise, in effect postponed taking final action for 90 days to give District Cablevision time to demonstrate that it can obtain the necessary financing.

District Cablevision insisted that it needed approval for a $32 million package of modifications to make its proposed cable system economically viable.

Under the revised agreement, the cable firm would have to begin construction no later than June 1, 1986, and would have five years to complete the system. The proposed residential network would be reduced from 78 channels to 54 and the proposed network for businesses would not be activated.

In addition, District Cablevision has until Sept. 1 to produce legally binding agreements with two key players -- Tele-Communications Inc. (TCI) of Denver and the Chesapeake & Potomac Telephone Co. -- and to develop a schedule showing when each neighborhood would receive service.

But some city officials predict that more negotiations will take place in September.

"All we did was to authorize them to see what they could put together," Smith said. "I think the council really has to make a decision about how badly it wants cable. It might be necessary to use some public financing if we want to have minority control and public access benefits."

District Cablevision President Robert L. Johnson said he plans to meet the city's conditions by mid-August. He also agreed that the negotiations are not over.

For example, the council rejected a modification that would have limited the cable firm's construction cost to an average of $500 per unit. Johnson said his company must have some provision to give the company relief if it runs into future financial problems.

In addition, although the council's emergency legislation rejected a proposed reduction in a $2 million security fund to $100,000 in cash, with the rest in an irrevocable letter of credit, Johnson said, "that's something we've got to negotiate."

TCI, the nation's largest cable operator, has offered to provide at least $30 million in funding to finance the cable project, according to District Cablevision officials. In exchange for the funds, TCI wanted what the council said it would not and did not provide -- approval for District Cablevision's entire package of proposed modifications.

TCI Vice President John Sie said he must review the legislation adopted by the council and would not say if or when his company would begin negotiating a legal agreement with District Cablevision.