How do Voyager 1 and 2 transmit messages from far away?

Spacecraft Voyager 1 and Voyager 2 transmit images of space and its contents from great distances, but how? Learn more about the technology that allows them to send radio messages from far, far away in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:00):
Welcome to brain Stuff from how Stuff Works dot com
where smart Happens. Hi, I'm Marshall Brain with today's question,
how are the Voyager spacecraft able to transmit radio messages?
So far? The two Voyager spacecraft certainly have an amazing

(00:24):
track record. They were sent to photograph planets like Jupiter, Saturn,
and Neptune, and they've just kept on going towards the
outer edge of the Solar System. Voyager one is currently
over ten billion miles or about sixteen billion kilometers away
from Earth and it's still transmitting. It takes about fifteen

(00:44):
hours for the signal to travel from the spacecraft to Earth.
The Voyager spacecraft used twenty three watt radios. For comparison,
your cell phone typically has a three watt radio inside,
So in the grand scheme of things, the voice Woyager
radios aren't really that high power in terms of transmitters.

(01:04):
Big radio stations on Earth transmitted ten thousand watts or more,
and they still fade out fairly quickly. The key to
receiving the signals here on Earth is therefore not the
power of the radio, but a combination of three other things. First,
NASA is using extremely large antennas. Second, those antennas are

(01:26):
directional and they point right at each other. And third,
the radio frequencies used by Voyager don't have a lot
of man made interference on them. The antennas that the
Voyager spacecraft use are huge. You may have seen people
who have large satellite dish antennas in their yards. These
are typically two or three meters or six to ten

(01:49):
feet in diameter. The Voyager spacecraft has an antenna that
is three point seven meters or about fourteen feet in diameter,
and it transmits to a thirty four meter a hundred
feet or so antenna on Earth. The Voyager antenna and
the Earth antenna are pointed right at each other. When
you compare your phone stubby, little omnidirectional antenna to a

(02:13):
thirty four meter directional antenna, you can see the main
thing that makes a difference in getting signals back from Voyager.
The Voyager satellites are also transmitting in the eight giga
Hurts range, and there's not a lot of interference at
this frequency. Therefore, the antenna on Earth can use an
extremely sensitive amplifier and still makes sense of the faint

(02:35):
signals it receives. Then, when the Earth antenna transmits back
to the spacecraft, it uses extremely high power tens of
thousands of watts to make sure the spacecraft gets the
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