The Alexandria Telecommunicatons Corporation's effort to win Alexandria's lucrative cable TV franchise got a major boost yesterday in reports submitted to the City Council.

The firm, which calls itself ALTEC and is headed by politically influential developer William L. Vosbeck Jr. and retired Democratic State Sen. Armistead L. Booth, was the overall choice of the city's own cable TV administrator. It got a rating of "unusually good" in terms of its financial structure from an independent financial consultant.

ALTEC is competing with two other firms for the franchise.

The reports, including one by a consulting engineer, found some merit in a proposal by the Alexandria Cable-vision Co. (ACC), a firm that includes former Virginia House Majority Leader James M. Thomson and former city council member James Carroll. None of the recommendations for ACC was as strong as the recommendations for ALTEC, however.

The reports, by financial consultant Lee A. Bertman, engineering consultant Warren L. Braun, and the city cable TV administrator Merry Sue Smoller, dealt a strong blow to the hopes of the Alexcom group headed by local investor Bruce G. Duncan. The three reports criticized Alexcom's financing and management proposals although praising some of its ideas for community involvement.

"I give preference to ALTEC because of its financial strength (including a contingency fund to minimize risk in system development), experienced management, . . . realistic projections, and the public services advantages I perceived" in the company's two-way televising system, Smoller wrote. Under a two-way system, viewers at home can actually respond or participate in broadcast shows.

As is standard with municipal reports produced by city manager Douglas Harman, the emphasis in these reports was on financial stability. The Bertman report praised the ALTEC proposal, which states it will receive $2 million from a General Electric subsidiary, and have total initial funds of $6.9 million. ALTEC is one-half owned by ARTEC, which runs a successful cable TV franchise in neighboring Arlington County.

In a similar situation involving redevelopment of the old Torpedo Factory buildings on the city's waterfront, the city staff recommended one firm because of its financial stability, but the council chose another whose design plans it found more attractive.

Vosbeck, president of ALTEC, is a major partner in VVKR/Redstone, one of the Torpedo Factory developers. Although the Vosbeck firm was not initially chosen to redevelop the Torpedo Factory, it merged with the winner, the Alexandria Waterfront Redevelopment Corp., within a week of the council's selection.

A public hearing on the three Cable TV reports will be held this Saturday. The council is scheduled to tentatively name a developer on June 19, then vote its final approval June 26.