Crystal receiver set 12

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Set 12 is suitable for receiving local stations, which can be heard via a modern 2x 32 Ω headphone.
This receiver has two tuning capacitors.
One is for tuning, and one is for impedance matching between antenna and tuned circuit.

Circuit diagram of set 12

Tuning capacitor C1 provides a matching between antenna and tuned circuit.
C2 and L1 form the tuned circuit.
L1 consists of 12 meter litzwire 36x0,07 mm with a tap on 50 % (6 meter).
The coil former is made of a cd from which the shiny layer is removed.
The cd has 9 slots through which the litzwire is wounded.

The diode is a schottky diode.
The transformer has an input impedance of about 44 kΩ, when the receiver is loaded with 16 Ω.

The components in the receiver.

The Q factor of the tuned circuit, not loaded with the diode is:
600 kHz: Q=105
900 kHz: Q=108
1200 kHz: Q=95
1500 kHz: Q=84
Because of the quite low Q, this receiver is not so suitable for receiving distant stations.

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