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Chapter 1: Decibels, Can You Hear Me Now?

You have probably heard of decibels, in the context of loud noises, rock concerts and similar. Decibels are also used in a radio context, and have a very similar meaning. In this case, the frequencies used are far beyond what humans can perceive – but the concept is the same, it represents “how loud is the signal from the other end?” Much of the content later-on requires that you understand decibels, so this section explains them to you.

You have probably heard of decibels, in the context of loud noises, rock concerts and similar. It is a logarithmic scale, doubling every 3 decibels (abbreviated to “dB”) in audible volume. So a whisper at 1 dB is half the volume of a whisper at 4 dB.

Decibels are also used in a radio context, and have a very similar meaning. In this case, the frequencies used are far beyond what humans can perceive – but the concept is the same, it represents “how loud is the signal from the other end?”

In the case of radio, you are often dealing with negative numbers. For example, your receiving radio may have incoming signal strength of -55 dB. The sensitivity threshold at which your radio can hear is also negative; for the sake of example, -75 dB. So long as the signal is more (less negative) than the receiving signal, all is well. So, -55 dB is audible; -80 dB would not be.

Despite the numbers being negative, the same basic principle applies to doubling in power every 3 dB. -55 dB is twice as strong as -59 dB.

Terminology

You will often encounter several terms that use decibels (dB) as a measurement. These include:

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