Page 109 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

FIGURE 7-4 Block diagram and schematic of a regenerative radio using a
secondary winding of one turn around the primary winding.
But what if one does not want to go through the trouble of winding wire around the
antenna coil and instead wants to use the existing secondary winding? Well, there
is a way to use the existing secondary winding. And two methods will be shown.
Figure 7-5 shows almost the same circuit as Figure 7-4, but it uses the existing

secondary winding of 10 to 20 turns.
Parts List

• Cl, cs: 1 ~F, 35 volts
• C2: 7 pF or 6.8 pF
• C3: 100 pF, 16 volts
• C4: 0.0033 IJF

• Rl: 100 k

• R2: 1 M

• R3: 1 k

• R4: 56 k

• RS: 10 k

• VR1: 1 k

or 2 k

• Tl audio transformer: 10 k

primary, 10 k

or 7 k

secondary
• Ll antenna coil: 470 IJH primary
• Vel two-gang variable capacitor: 140 pF, 60 pF

• 01, 02, 03, 04: lN914
• Ql, Q2: MPSH 10
In this version, VR1, the regeneration control, is connected across the secondary
winding of L1. The regeneration signal current from Q2 is fed to the wiper of VR1,
which can divert this signal current to the +3-volts supply voltage and/or to the

secondary winding. That is, part of the signal current from Q2 can be fed to the