What is Noise Figure and Why is it Important
Every TV amplifier generates a certain amount of internal noise that is added to the signal that it amplifies. A measurement of this noise amount is expressed in a value called Noise Figure. You want to select a TV amplifier with the lowest noise figure possible.
Think of nice green lawn in your yard. Then place a basketball, a soccer ball, a golf ball and several marbles spread out on the lawn. The different size balls represent signals from TV transmitters in your area. The largest ball represents the strongest TV signal. The weakest signals are represented by the marbles. The height of the grass represents the noise figure of the TV amplifier you are using. The taller the grass the higher the noise figure of the TV amplifier. We will start with the grass being 6" tall. With the grass this high you can only see the basketball and the soccer ball. The golf ball and the marbles are lost in the tall grass. So when using a high noise figure TV amplifier, you will only be able to receive the stronger signals represented by the larger balls. The weaker TV signals are not usable because they get lost within the noise generated by the amplifier. So now if you switch to a TV amplifier with very low noise figure it is like cutting the grass to 1/4 inch level. All of a sudden all of the balls are visible and thus your TV can receive more channels.