The location of the antenna is one of the most important elements of signal reception for radio waves. DTV is using the same frequencies for the stations as before except that channels below 7 are no longer in use. Those stations had to move to higher frequencies. An example of this is Washington’s WRC, Channel 4, which is now using the frequencies that had been for channel 48: 674 – 680 MHz. The old channel 4 frequencies were 66 – 72 MHz.
I have a very good example of the differences in signal reception due to antenna location at my house. I have three antennas, two of which are the same home-designed and built antennas (my wife called them my porcupine antennas.) The building and testing with photos is on my web site at: Antennas.htm – March 04, 2012
Now, one antenna is on the western-most location of my house, up about 30 feet above the ground. A second identical antenna is located about four feet above the ground and about 70 feet to the east, inside my garage.
The third antenna is a combination of a VHF antenna and a high-gain UHF antenna. It is located in my attic up about 20 feet above ground and about halfway between the east and west-located antennas.
There are times when the only antenna which can receive Channel 26 from Washington, D.C., is the antenna in the garage, lower and furthest east. I believe that this is because it is in a location that has a clear path to that particular TV station’s antenna. My point is simply that unless we test every conceivable antenna location and height, we will never know if the antenna we install is really at the optimum location for all the stations we wish to receive. This is, to put it mildly, a very daunting task.