[ADTech]

His antenna receives that frequency just fine, there's nothing wrong with it. It's a frequency-specific "dead spot" due to an unfortunate confluence of a small signal blockage or reflection that just happens to coincide with the spot where he plopped the antenna down which just happens to coincide with the operating channel that carries his NBC affiliate. I see such issues every day, especially in attics. If you look at such an impaired signal on a spectrum analyzer as I have, the signal will have a large void somewhere in the 6 MHz bandwidth. Move the antenna and the problem moves away, or at least, somewhere else, and hopefully not into a different channel that is also occupied.

Let's not try to overthink this, go with the most logical possibility that's easy to resolve.