How did vacuum tubes make radio broadcasting and long-distance telephony possible?

Vacuum tubes were essential to the development of radio broadcasting and long-distance telephony because they provided the ability to rectify and amplify electrical signals, which were previously weak and unreliable.123

Radio Broadcasting

Early radio reception relied on undependable devices like the "cat whisker" detector, which lacked sensitivity. The invention of the two-electrode vacuum tube, or thermionic valve, allowed for the efficient rectification of high-frequency alternating current into direct current, enabling clearer signal detection. The subsequent development of the three-electrode vacuum tube, or Audion, by Lee De Forest was a breakthrough; it allowed small variations in grid potential to control large amounts of current, effectively amplifying radio signals.14

Long-Distance Telephony

Long-distance communication faced significant signal attenuation, where the strength of the signal faded over long wire circuits. While loading coils helped reduce this loss, they were insufficient for transcontinental distances. Vacuum tube circuits provided the necessary amplification and regeneration of weak signals, making truly long-distance and transcontinental telephony commercially viable. These tubes also enabled carrier multiplexing, allowing multiple voice channels to be transmitted simultaneously over the same lines.25