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The Telecommunication Act of 1996 says that, "The rules apply only to an individual who owns or has exclusive use of the area in which he or she wants to install one or more antennas. Under the guidelines, association restrictions which prevent, unreasonably delay, unreasonably increase the cost of antenna installation, maintenance or use, or preclude reception of an acceptable quality signal will no longer be enforceable.
In addition to these guidelines, masts to which MDS antennas are to be attached may be prohibited if more than 12 feet above the roofline. Restrictions designed to implement a clearly defined safety objective, or maintain the nature of a historic district, are exempt from the rules. In exceptional circumstances, an association may petition for a waiver of this rule."
Since the attic antenna costs more, the association is not permitted to force him to buy one. The only possible exception would be if he owns a condo and wants to put it on "common property" or if the structure is ruled "historic".
Federal Law supersedes ANY local or HOA law. Also check out the FCC homepage at http://www.fcc.gov.