With the advent of cable and direct TV, TV antennas are not too common anymore. But if you look around a neighborhood, you may still see a couple of homes with the good old metal contraption on the roof. It's hard to believe something so spindly looking can actually serve a purpose, but they have been bringing the gift of entertainment into people's homes for decades.
The antenna is made up of a central piece of metal, or boom, crisscrossed by a series of metal rods. The boom contains receptors, or elements, designed to pick up TV signals, with two rods assigned to each. These rods receive the TV signal sent from TV transmission towers, which are typically located on a hill or rooftop near each TV station. The antenna will only receive signals sent on a TV frequencies--either VHF, UHF or both--which is why it won't pick up radio or cell phone noise, for example. Once the antenna picks up the signal, it travels through the cable that's connected to the TV, where it is then translated into audio and video, allowing an individual to view a TV show.
It helps to have the antenna's rod pointed in the direction of the transmitter, which is why the signal sometimes gets better when you send someone up on the roof to adjust it. Also, the size and number of rods on the antenna can make a difference. If your antenna has more rods, signaling additional receptors, it can accept a larger variation of channels. A larger boom size can help it to reach signals that are further away.
Some people that rely on analog TV do not have roof antennas, but instead antennas on their actual TVs, known as "rabbit ears." These antennas function in a similar manner to roof antennas, with the two metal sticks serving as both the rods and the boom. As anyone who has worked with these antennas will tell you, it is quite the game of push and pull to try to get a good signal, since you need to move the antenna one way in order to pick up a good signal from one transmitter and another in order to pick up another, depending on the channel you want to watch at any certain time. This frustration is what sent many homeowners to the roof and eventually to the cable box.