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All you have to say is that you cannot receive certain stations when the antenna is mounted in the attic. Once you say that, they have no recourse based on FCC rules. The only other rules that would apply would be safety laws and regulations on mounting the antenna or dish.
From the FCC page:

Q: What restrictions prevent a viewer from receiving an acceptable quality signal? Can a homeowners association or other restricting entity establish enforceable preferences for antenna locations?

A: For antennas designed to receive analog signals, such as TVBS, a requirement that an antenna be located where reception would be impossible or substantially degraded is prohibited by the rule. However, a regulation requiring that antennas be placed where they are not visible from the street would be permissible if this placement does not prevent reception of an acceptable quality signal or impose unreasonable expense or delay. For example, if installing an antenna in the rear of the house costs significantly more than installation on the side of the house, then such a requirement would be prohibited. If, however, installation in the rear of the house does not impose unreasonable expense or delay or preclude reception of an acceptable quality signal, then the restriction is permissible and the viewer must comply.

The acceptable quality signal standard is different for devices designed to receive digital signals, such as DBS antennas, digital broadband radio service antennas, digital television ("DTV") antennas, and digital fixed wireless antennas. For a digital antenna to receive or transmit an acceptable quality signal, the antenna must be installed where it has an unobstructed, direct view of the satellite or other device from which signals are received or to which signals are to be transmitted. Unlike analog antennas, digital antennas, even in the presence of sufficient over-the-air signal strength, will at times provide no picture or sound unless they are placed and oriented properly