What makes digital broadcast transmission (like over-the-air TV) need less power (as little as 25%) to cover the same area as the previous analog transmitter?
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Let’s imagine it as you having a shortwave handheld radio. You and your friend can speak back and forth over it. At some distance the interference from other signals and just the atmosphere in general will make the meaning of the speech unrecognizable. You’ll be able to recognize it as human speech but the actual words will be garbled beyond recognition. This is much like an analog signal.
Now let’s say you and your friend are fluent in Morse code. Just a series of beeps. The beep itself conveys no information other than the fact that it is a beep. So as long as the reciever can clearly hear the beep they have received a part of the message. The tone of a Morse beep can clearly be distinguished even through a ton of static. Thus using the same handset with the same amount of power, you’re able to transmit clear messages over much greater distancea because the same amount of interference has a lesser effect on the information being transmitted.
It also means that you can drop the power of the transmitter to only be understood at the same range as the voice message. Now you have the same information, over the same range, using less power.
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