The figure below shows a block diagram of a table-top AM radio from the late 40’s where the radio tunes in stations at the frequency frf = frequency of OSC1 – 455 kHz.

[Jeff Geerling] recently visited a tower site for WSDZ-AM, which uses a full eight towers to broadcast its 20kW AM signal. To do that, it needs a phasor to keep everything in tune. Or, uh… phase.