These truly are remarkable achievements of man-kind. If you’ve been curious to know about the science and technology behind these extraordinary operations, then you’re in luck. The following are the best explanations the internet has to offer regarding this.
Mobile phones work off UHF (Ultra High Frequency), so the range is very short. There are usually signal repeaters across a country, so it gives the impression mobiles work everywhere.
Wouldn’t this take an enormous amount of power?
So, not really, as long as there is nothing between Voyager and the receiving antenna (usually very large). As long as the signal is stronger than the cosmic background, you’ll pick it up if the antenna is sensitive enough.
With little to no Oxygen/other gases in space relative to Earth’s atmosphere, so they don’t have to worry about rust/corrosion. So then they’d just be protecting it from electromagnetic and radiation.
They used a very large dish to focus the transmissions into a narrow beam. The bigger the dish, the greater the effective power. A 70M dish has a gain of around a million (depending on the frequency).
They also used very low bit rate communications. The usable bit rate is highly dependent on signal to noise ratio.
They do use high power on the Earth side, but the spacecraft has only a few watts, and a small dish. The Earthbound receivers use ruby masers cooled in liquid helium to get the lowest noise.
If you put a 1,000 watt signal into an antenna with a gain of 1,000,000, it doesn’t suddenly magically put out 1,000,000,000 watts.
In antennas, gain is about signal intensity compared to an omnidirectional antenna (an antenna that sends an equal amount of energy in every direction).
So, let’s say you have an omnidirectional antenna transmitting 1000 watts.
You have a small antenna a long way away receiving this signal. The small antenna picks up 0.000001 watts of the signal (one millionth of a watt).
Now, you switch to a highly directional antenna, pointed directly at the receiving antenna. Instead of sending power out in all directions, the directional antenna sends all the power in a tight cone towards the receiving antenna.
Let’s say that now, using the highly directional transmitting antenna, the receiving antenna picks up 1 watt of signal. That’s 1,000,000 times as much signal as it got when the antenna was omnidirectional. The highly directional transmitting antenna has a gain of 1,000,000.
Note, however, that you get LESS signal in any direction the antenna isn’t pointing – with the omnidirectional antenna, you got the same signal regardless of antenna orientation. With the directional antenna, if the antenna is pointed just a little bit wrong, the signal will be much WORSE than with the omnidirectional antenna.
One thing that they do in order to make communication with these spacecraft more reliable is to send the same batch of commands multiple times, each with a very slight frequency offset. This accounts for any relative velocity variation between Earth and the spacecraft, which may receive 3 of 5 commands sent, for example. The signals from the Voyagers are not strong – they are, in fact, weak compared to the background noise, but clever software algorithms have been developed which identify and isolate these transmissions.