Loud and clear: ham radio’s calling cards
Rummaging around collections of old photographs and postcards I have often wondered about these peculiar cards, emblazoned with strange letters and numbers, that sometimes turn up, usually in groups of several. I could guess they were connected with amateur, or "ham" radio operators, but their purpose remained a mystery until recently, after I found a few more, when I decided to find out about them. It didn't take long to discover that they are known as "QSL" cards and that radio operators use them to let one another know when they have received each other's signals.…
