When you install your new antenna and signal amp, make sure you install the amp as close to the antenna as possible. The best location is right at the top of the mast, directly below the antenna. The further from the antenna, you are amplifying the noise along with the signal.
70 miles is really pushing an OTA signal, especially at UHF frequencies. Because of homeowner covenants, my antenna is installed inside my garage, up against the ceiling. The ceiling happens to be 12' high, and my home is several hundred feet above the valley floor. But even with a pretty good sized yagi antenna (about a 7 foot boom, but no amp), and most of my stations are 35 miles or less from me, I can still encounter pixelization on occasion on a few channels. I have one station only 20 miles away, but terrain causes issues with it, and only some of my TVs can actually tune it.
I have one station that is exactly 102 miles from the transmitter to my home. On the rarest of occasions it might actually show up on one of my sets. I have a direct line with it, and my antenna is pointed straight at it, since most of the other sites are along the same line. If it was on a VHF channel I might get it more reliably, but it's on RF channel 14, which is 473 MHz. That's a very long distance for that frequency. I just manually tuned it on my LG Nano85, and it's actually coming through, abet not really watchable with the pixelization and break up. If I added an amp to my antenna, I doubt it would make much difference. It's just too fringe of a signal.
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