The two Voyage spacecraft have had an amazing track record. They were sent to photograph planets like Jupiter, Saturn and Neptune and have just kept on going past the outer edge of the solar system. Voyager 1 is currently over 7 billion miles (about 11 billion kilometers) away from Earth and is still transmitting — it takes about 10 hours for the signal to travel from the spacecraft to Earth.
The Voyager spacecrafts use 23-Watt radios. This is more than the 3 Watts a typical cell phone uses, but in the grand scheme of things it is still a low-power transmitter. Big radio stations on Earth transmit at tens of thousands of Watts and they still fade out fairly quickly. Seven billion miles away, 23 Watts output – this equals to 304.347.826 miles per Watt…. beat that!