Is there a set of specs and / distances to narrow down the choices or to know how to choose an HD antenna that could replace my cable provider for access to local channels?
you want the highest gain in Db for the antenna. If an amplified model high gain Db with the lowest noise S/N (signal/noise ratio). Not always are the most expensive the best. The last thing is location, the higher you can mount it the better. When looking at Db a difference of 3 is big 2x the signal.
I wondered the same thing when I shopped for an antenna. Unfortunately, I couldn't find a set of specs or a way of comparing antennas from different manufacturers. All I found were reviews but they were all subjective and didn't help me rank one antenna over another, especially when the antennas were from different manufacturers.
That's when I bought various antennas and tested them myself using a Winegard Signal Strength Meter and my Tivo. Using the Winegard (which I have no affiliation with) was a very objective way of comparing them because you select a frequency and it gives you a signal strength.
I test the antennas in two different ways. For the first test I rotate the antenna for each frequency and record the maximum signal strength. For the second test I point the antenna in the same direction and leave it stationary (which is how most people use an antenna). I then run through the frequencies and record the results.
Even though I can only test the frequencies in my area, I figured these results might be useful to others so I put them on my website at: http://byebyecabletvbill.com/tv_antenna_side_by_side_comparisons.php. As time progresses, I'll be testing more antennas and adding the results there.