In this Amplitude Modulation circuit, what is the purpose of the diode load (L2)?
A picture is worth a thousand words.


The carrier and audio modulating signals are simply added but do not form a modulated signal. 

The diode rectifies this signal forming a crudely modulated signal which contains a DC component, low frequency component and high frequency component.

The inductor acts as a low impedance for the low frequency component and high impedance for the high frequency. 

The capacitor blocks the DC component but passes the high frequency AC signal 

The tuned LC circuit filters out all but the the desired AM signal.