A hundred years ago this month, the April 1921 issue of Radio News showed how to build this simple receiver, said to have a cost of only 25 cents. Tuning was accomplished with a variable capacitor consisting of aluminum plates separated by waxed paper. By compressing the plates, the capacitance was changed.

The magazine lamented that there were probably thousands of lads who looked wistfully at the catalogs, only to be discouraged by the high prices. The thought was that if they got a chance to listen in with this inexpensive set, they would be sold on the idea of radio and would soon figure out a way to put together a more impressive station.

Accroding to the magazine, almost every town had a good amateur station holding court on 200 meters, and receiving them even with this simple crystal set would be a simple matter.

I have no doubt that the parts shown here could be had for a quarter. The problem, however, is that the prospective radio ham would still need a headphone with which to connect the set. Looking through the magazine, the least expensive was $4.50, or about $66 in today’s money, according to this inflation calculator.

Those headphones, of course, would still be good when the listener was bit by the radio bug and upgraded to a better set. But the cost of entry to the hobby was $4.75, and not the 25 cents promised by the magazine.