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Pick it up. Put it down somewhere else. Raise or lower the antenna. Repeat as needed.

The incoming signals are not homogenous, that is, not of uniform strength and quality. This results in "dead" spots for certain channels, a situation that an attic location only makes worse. It's your goal (and mission), to continue trying spots to see if you can find one where everything "plays nice" and works. This would be referred to as a "sweet" spot. For UHF frequencies, the difference between a dead and a sweet spot can be as little as 6-12".