Page 107 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

So here is a first somewhat successful transistorized regenerative radio using an

internal antenna.
Parts List
• Cl, CS, C6, C7: 1 J..IF, 35 volts

• C2: 7 pF or 6.8 pF
• C3: 0.01 J..IF
• C4: 0.0033 J..IF

• Ri: 100 k

• R2, R6: 1 M

• R3: 1 k

• R4, R7: 56 k

• RS: 10 k

• VR1: 100 k

• Tl audio transformer: 10 k

primary, 10 k

or 7 k

secondary
• Ll antenna coil: 470 J..IH with 1 turn wrapped
• VCl two-gang variable capacitor: 140 pF, 60 pF
• 01, 02, 03, 04: 1N914
• Ql, Q2: MPSH 10

• Q3: 2N4124 or 2N3904
This was really the first circuit that worked in a similar way to the pentode
regenerative radio featured in EDN Magazine. The trick here was that only one turn
was used for the secondary winding to provide the positive feedback for

regeneration. And that one turn of wire [e.g., 30 American Wire Gauge (AWG)] was
located in the center of Ll's primary winding.
Diodes D1 to D4 form a voltage reference of about 1.6 volts to 2.0 volts for
providing a DC bias voltage to Q1. Resistor R3 (1 k

) and capacitor C2 form a network to ensure that Ql does not oscillate parasitically.
As seen here, the RF signal is picked up by the antenna coil Ll primary and is