Fairfax County Circuit Court Judge F. Bruce Bach upheld the county's cable television franchise yesterday and said he would dismiss a suit challenging it within the next 10 days unless the firm that lost the award could come up with new evidence.

Such an action would remove the last remaining major obstacle facing Media General Cable of Fairfax County Inc., which last year won the coveted cable franchise. It already has begun construction of the multimillion-dollar system.

Fairfax Telecommunications Co., which lost the franchise, sued the county earlier this year in an effort to block the award, alleging that county officials unfairly "conspired and cooperated" to allow Media General to improve its application after the filing deadline.

Bach rejected those complaints and held that the county acted properly in awarding the franchise. The judge said in a letter to the attorneys that "allowing an amendment to Media General's application was not a violation of any ordinance."

Fairfax Telecommunications has "not alleged any behavior by the defendants, other than allowing Media General to amend its application, which would constitute arbitrary and capricious behavior," the judge said. "Absent such allegations of fact, the bill of complaint must be dismissed."

Bach said he would give Fairfax Telecommunications 10 days "to allege, if possible, what actions by the county board constitute arbitrary and capricious behavior. If they cannot then this matter shall be dismissed."

"Our process has been vindicated and the decision itself has been vindicated," said County Board Chairman John F. Herrity shortly after the judge released his decision. "I think the process the county developed was a fair process and an open process and it allowed the best quality applicant to get the franchise."

"My concern was that the litigation was going to hold up service," said Supervisor Audrey Moore.

"We're pleased and we hope that in 10 days we'll be more pleased," said Media General spokesman Lorraine Foulds.

Fairfax Telecommunications attorneys could not be reached for comment.

Media General and Fairfax Telecommunications were the only two bidders for the 15-year franchise, which a consultant estimated could be worth $260 million at the end of the franchise. Several national cable companies dropped out of the bidding, some complaining of the county's complicated and time-consuming franchise requirements.

The battle between the two companies was acrimonious, with Fairfax Telecommunications asserting that the county showed favoritism in awarding the franchise to Media General, a charge county officials denied. Fairfax Telecommunication also insisted that Media General lacked experience to handle the job.

Media General, a subsidiary of the communications company that owns Richmond's two daily newspapers, recruited five influential local citizens as stockholders.

Fairfax Telecommuncations was a partnership between more than 200 local residents, many of them politically prominent, and a Denver-based cable firm, Tele-Communications Inc. It hired Andrew P. Miller, former Virginia state attorney general, and retiring state Sen. Adelard L. Brault, to handle the suit challenging the award.

Another potential barrier to the implementation of cable service was also recently resolved. The Federal Communications Commission ruled against Warner Amex Communications of Reston, which wanted the FCC to deny Media General an application for a microwave transmission license in the county.

Warner Amex has supplied cable TV service in Reston for more than 12 years under a contract with the community's developers, but it does not have a government franchise. Fairfax's regulations require that Warner Amex cease operation there after Media General begins operations.