From what I learned about TV signal and antenna's is that height is a variable based on where you are in relation to signal. The signal passes through the air as a wave running up and down bouncing off the Earth and I guess the clouds or upper atmosphere. So if you are at a location where the signal is about to bounce off the Earth higher would be more harmful to capturing signal than good. How do you find out where you are. Great question and glad you asked. I have no idea
I am sure there is some formula based on wave length and distance but I do not know what it is.
Another tip I was given by antenna people was to drop the nose of the antenna anywhere from 5 to 15 degrees. Remember the wave? Putting the antenna on a pitch gives better ability to trap signal.