1937 Two Dollar Radio
In 1937 enthusiasts could purchase a simple radio kit for $2. Of course if it was to work, the lad would have to buy the chassis and front panel to mount all the parts, plus the batteries, an earphone and a few more tuning coils. Thus for about $7 one would have a fairly serviceable receiver covering 10 to 550 meters (30 to 0.4 mHz.)
No doubt this would be a sensitive super-regenerative model, very simple in design and easy to construct.
The sensitivity came from the circuit feeding back on itself at the receive frequency, almost to the point of breaking into oscillation. If it did break into oscillation, then it would transmit on the frequency to which it was tuned, causing a whistle in any neighbour's receiver tuned to the same station. This was a major complaint to the radio inspector authorities--see some of the newspaper clippings on this site regarding this complaint here.
The Radio World for September 1937 is available here as a PDF. An interesting read--including some early television information.