A plan to build a distributed antenna system to boost cell phone coverage in the three up-Island towns took a step forward this week when Aquinnah and Chilmark approved plans by American Tower Company to build the system. Approval came during a four-hour meeting between the towns on Monday at the Chilmark Community Center.

But the plans took a step backwards when Aquinnah officials determined the vote by the planning board review committee was invalid because only five of seven members were present.

So the review committee’s 3-2 vote to authorize American Tower to start building along the town public ways will be thrown out, and a new vote by the full committee will be required.

Meanwhile, in a separate vote, Chilmark’s 13-member plan review committee voted 10-3 in favor of the DAS system, clearing the way for American Tower to start siting a series of nodes with whip antennas around town.

The marathon meeting on Monday was one part of a busy week for the DAS proposal. On Wednesday representatives for American Tower appeared before the West Tisbury zoning board of appeals for a pre-application hearing that is required under a town cell tower bylaw approved by voters in 1999.

Under the bylaw, an applicant seeking to build a cell tower must appear before the zoning board for a preliminary review at least 30 days before formal plans are submitted. Wednesday’s meeting served as an opportunity for the public to ask questions.

The current plan from American Tower calls for 55 node locations: eight in Aquinnah, 24 in Chilmark and 23 in West Tisbury. The system would use a combination of existing stub poles and new poles, and would string fiber optic cable along approximately 1,200 existing utility poles owned by NSTAR.

American Tower submitted the plans in response to a request for proposals from the up-Island DAS committee, which includes representatives from Aquinnah, Chilmark and West Tisbury. The committee was formed in 2005 after Aquinnah blocked the cell phone provider Cingular (now AT& T) from leasing the steeple of the Aquinnah Community Baptist Church for use as a cell tower.

The phone company sued the town under the provisions of the Telecommunications Act of 1996, which guarantees citizens rights to quality cell service and limits the grounds on which towns and citizens can challenge the construction of cell phone towers.

The DAS committee was created to form a plan to boost cell phone service in all three up-Island towns, although a growing number of West Tisbury residents and some have called for the town to drop out of the agreement, partly because the town already has better cell service than the two other towns.

At Wednesday’s meeting in West Tisbury, a number of people suggested that a traditional cell tower might be a better solution than a DAS system. Zoning board member Tucker Hubbell said the committee should have come up with several scenarios.

“I have no fault with [American Tower]. I have fault with the committee . . . there should have been town meetings or public hearings where you could inform the public about DAS and cell towers and say: this is what we can do for you based on the type of coverage you are looking for,” Mr. Hubbell said, “I don’t think they investigated all the choices.”

But selectman Richard Knabel, one of the town’s two representatives on the up-Island DAS committee, said the committee focused on a DAS system because there were indications the three towns did not want cell towers.

“Part of the agreement was to examine whether a DAS system — and specifically a DAS system — had an application and advantage to us. It was not a coverage committee as such . . . Chilmark and Aquinnah had expressed in their own way they didn’t want towers — and so did West Tisbury,” Mr. Knabel said.

He cited the 1999 cell tower bylaw as evidence that West Tisbury residents opposed cell towers. “We had eight pages of zoning bylaw that was written to make it difficult to build new towers. The implicit understanding was that towers were not something we wanted,” he said.

Mr. Tucker disagreed, noting the zoning board had approved applications for three new cell towers since the bylaw was approved 10 years ago “You make it seem the [bylaw] was written to make it impossible to approve cell towers in town . . . yet we have already approved three new cell towers . . . I’m incredulous that you can make that statement,” he said.

While debate flared between the town officials, the American Tower representatives — attorney Ken Spigle and strategic relations project manager Tamara Slade — stayed out of the fray.

“This is an interesting discussion, but I am not sure what it has to do with our application,” Mr. Spigle said.

At Monday’s meeting, American Tower’s Alex Gomata said his company would prefer to build a cell tower because it is cheaper and provides better coverage. He also said American Tower can proceed with a DAS system without West Tisbury. “But our preference is to have all three towns,” he said.