Speaker 1: Welcome to brain Stuff from how Stuff Works dot com
Speaker 1: where smart Happens. Hi, I'm Marshall Brain with today's question,
Speaker 1: how are the Voyager spacecraft able to transmit radio messages?
Speaker 1: So far? The two Voyager spacecraft certainly have an amazing
Speaker 1: track record. They were sent to photograph planets like Jupiter, Saturn,
Speaker 1: and Neptune, and they've just kept on going towards the
Speaker 1: outer edge of the Solar System. Voyager one is currently
Speaker 1: over ten billion miles or about sixteen billion kilometers away
Speaker 1: from Earth and it's still transmitting. It takes about fifteen
Speaker 1: hours for the signal to travel from the spacecraft to Earth.
Speaker 1: The Voyager spacecraft used twenty three watt radios. For comparison,
Speaker 1: your cell phone typically has a three watt radio inside,
Speaker 1: So in the grand scheme of things, the voice Woyager
Speaker 1: radios aren't really that high power in terms of transmitters.
Speaker 1: Big radio stations on Earth transmitted ten thousand watts or more,
Speaker 1: and they still fade out fairly quickly. The key to
Speaker 1: receiving the signals here on Earth is therefore not the
Speaker 1: power of the radio, but a combination of three other things. First,
Speaker 1: NASA is using extremely large antennas. Second, those antennas are
Speaker 1: directional and they point right at each other. And third,
Speaker 1: the radio frequencies used by Voyager don't have a lot
Speaker 1: of man made interference on them. The antennas that the
Speaker 1: Voyager spacecraft use are huge. You may have seen people
Speaker 1: who have large satellite dish antennas in their yards. These
Speaker 1: are typically two or three meters or six to ten
Speaker 1: feet in diameter. The Voyager spacecraft has an antenna that
Speaker 1: is three point seven meters or about fourteen feet in diameter,
Speaker 1: and it transmits to a thirty four meter a hundred
Speaker 1: feet or so antenna on Earth. The Voyager antenna and
Speaker 1: the Earth antenna are pointed right at each other. When
Speaker 1: you compare your phone stubby, little omnidirectional antenna to a
Speaker 1: thirty four meter directional antenna, you can see the main
Speaker 1: thing that makes a difference in getting signals back from Voyager.
Speaker 1: The Voyager satellites are also transmitting in the eight giga
Speaker 1: Hurts range, and there's not a lot of interference at
Speaker 1: this frequency. Therefore, the antenna on Earth can use an
Speaker 1: extremely sensitive amplifier and still makes sense of the faint
Speaker 1: signals it receives. Then, when the Earth antenna transmits back
Speaker 1: to the spacecraft, it uses extremely high power tens of
Speaker 1: thousands of watts to make sure the spacecraft gets the
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