Unseen signals all around us
Mike P
The space around us is filled with unseen waves that carry all kinds of information hither and thither.
By various technical means it is possible to detect and interpret some of these waves.
When people hear the word "radio" they often imagine a DJ playing records, talking over the best bits and sometimes interjecting the odd advert break, but the word has a more technical meaning too; WiFi, Bluetooth and mobile broadband are some of the modern applications of radio technology. Here I use the word in its more technical sense.
Satellites
Artificial moons which orbit the Earth
Repeaters
Amateur radio repeaters near Ely