Vinyl when riding the car

[Electronic M]

There were also practical reception issues. FM due to its shorter wavelength was prone to reflection cancellation. Regularly at lights I stop in a spot loose reception and have to creep forward a meter or 2 to try and recover reception. AM typically won't peter out as quickly or completely in those circumstances as well as under overpasses or in tunnels.
Also 50KW and higher power AM stations have larger coverage areas so on all day/all night road trips you might be able to drive the whole way without having to change from your favorite station (this plot device was used in the film Vanishing Point IIRC). There were some stations in Mexico that ran 100KW or higher (exceeding US station power limits) that played top 40 US hits with English language DJs that could be heard almost nation wide in the USA.