In 1932, the Federal Radio Commission (later supplanted by the Federal Communications Commission), banished from the airwaves fortune-tellers, mystics, seers, and other people peddling dubious claims, but concern remained about what was fit to air and how to enforce rules about truth in advertising. A 1936 edition of Hygeia, a publication of the AMA, lamented that “no adequate and prompt measures are as yet available to curb venal radio stations from selling ‘time’ to anyone who pays the price.”These Mexican radio stations broadcast with up to a million watts of power, reaching across the US and beyond. That's how John R. Brinkley advertised his surgery to implant goat gonads in humans, and made a fortune. Of course, the marketing of dubious quick cures continues on the internet. Read about the era of quack cures on the radio at Atlas Obscura.
And when regulators did catch up with fraudsters, enterprising quacks got creative. By setting up towers and transmitters in small towns south of the United States/Mexico border, a phalanx of fabulists launched their own stations, beyond the reach of many regulations.