Amateur "ham" radio operators (so called due to their unwieldy "ham-fisted" operating of morse code telegraph keys in the early days of radio development), have been around since the turn of the 20th century. And although Millennials may consider amateur radio as an antiquated, obsolete hobby, nothing could be further from the truth.
Admittedly the number of amateur radio operators has significantly decreased in the last four decades, but they are still thriving as a low-key, tight-knit group of airwave enthusiasts. Even in today's technologically driven world, they will often appear prominently during times of natural disasters, as well as political and social unrest. Their ability to continue transmitting when digital and satellite communications are interrupted, have made them all the more invaluable due to high tech's vulnerability.
With regard to memorabilia, QSL cards are highly sought-after collectibles by amateur radio fanatics. As defined by Wikipedia, QSL cards are postcards - sent through the mail - and serve as confirmation of the reception of an amateur radio broadcast between two ham radio operators. They are called QSL cards after the universally defined radio Q code for the confirmation. Collecting of these cards first gained popularity with radio listeners in the 1920's and 1930's, and the reception reports were often used by early broadcasters to gauge the effectiveness of their transmissions (think of it as data-mining in today's tech terminology)
|Record auction-priced QSL postcard from 1923|