The simplest radio circuit
Among them, L1 and C1 form a tuning circuit, VD and C2 form a detection circuit, and L1 and L2 form a coupling circuit.
Signal waveform before and after detection: 
The advantages and disadvantages of direct radio:
Advantages: simple circuit, small size, low cost, easy to carry and manufacture.
Disadvantages: low sensitivity and poor selectivity.
The advantages and disadvantages of heterodyne radio:
Advantages: high sensitivity and good selectivity.
Disadvantages: The circuit is complex, the cost is slightly higher, and the production is difficult.
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