Aerials
An aerial is something that receives a radio signal and converts it into an electrical signal. The radio signal is in the form of electromagnetic waves with a frequency between 30 and 300,000,000,000 Hertz. The size and shape of an aerial depends on the type of signal it is receiving and where the transmitter is.
The most obvious aerials in the streets around us are television aerials. Since TV transmitters are in fixed positions the aerials can point towards them to get the best signal. If you look at the TV aerials around you you will see they all point in the same direction. Can you see any that don’t? (These might be pointing to different TV transmitters). Can you think of an aerial that cannot point at the transmitter all of the time?
The bigger the aerial the fainter the signal it can receive - this is why radio telescopes that look for radio signals from space have to be so large. The largest is 500m in diameter at Dawodang in China
Other aerials are much smaller like the ones in a mobile phone which may have many different aerials (for the phone signal, WiFi, GPS, Bluetooth, NFC, etc).
For more information:
https://www.electronics-notes.com/articles/antennas-propagation/antenna-theory/basics-tutorial.php