You know that old joke that goes, “what are the 3 most important things to look for in real estate?” You’ve heard the answer: location, location, location. Well, the answer isn’t too different when you’re talking about antennas. Except, in this case, it’s one very specific type of location.
Height, height, height
That’s right, as far as I’m concerned, the most important thing about where you put an antenna is how high it is. Not how it’s aimed, not even if it’s sideways. Height is more important than any of those things. Height is probably more important than what model antenna you buy, unless you’re trying to compare two vastly different sized antennas.
So what makes me say that?
An antenna’s performance is measured in dB gain. Since a dB is a measure of “how much more” of something you have, antennas are measured by how well they perform compared to something else. That usually means how much better they do than a reference antenna in a lab. Unamplified antennas have from about 3 to about 20 dB of gain. Amplified antennas have more but they do that by adding gain to what the antenna can actually receive. If the antenna can’t receive a channel, the amplifier doesn’t do anything.
What you need to realize is that everything in front of that antenna cuts down its gain. If it’s inside, take out 1-3dB for the construction of the house. If it’s behind a tree, take out up to 3dB for that. If there’s another house in the way you could be looking at losing another 6dB depending on construction and how much of the signal is blocked.
When you look at it that way, you have to realize that the most important thing to do is get that antenna a clear view of the towers.
And that takes height.
It’s not just the stuff you see.
In most cases you can see about 5 miles in any direction. Beyond that, even on the clearest day, a distant house is going to be too small for you to see. That doesn’t stop that house from blocking the signal. You need to put that antenna up high enough so it gets past the stuff you can’t see.
This graphic is a little exaggerated, but it does show how the very roundness of the planet works against you. Because the earth is round, it rises up between you and the towers and that means that even ground-based obstructions are a problem. Another reason to get that antenna as high as possible.
How high is high enough?
That answer will be different for everyone. However, start by putting the antenna at the tallest point on your roof. If you get all the channels you want, great. If you don’t, go higher. Put up a taller mast, maybe one with guy wires, and see if it makes a difference. If you’re really serious, be prepared to go up 25-30 feet. Just know that if you go higher than 200 feet above ground level, you’ll actually need to put up obstruction lighting. There could also be local ordinances that keep you from going up that high.