Page 141 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

• Q6: 2NS089 or 2NS088
• LI antenna coil: 330 IJH primary, 10 to 20 turns for secondary winding
• T1: 42IF101 IF transformer with internal capacitor removed, or a 120-IJH or
1S0-IJH variable inductor
• T2, T3, T4: 42IF101 IF transformer

• Vel variable capacitor: twin gang 270 pF and 270 pF
• VR1: 100-k

pot
Figure 9-4 presents a schematic diagram of the alternate low-power

superheterodyne radio. In this configuration, the oscillator tank circuit formed by
VC1, C16, and T1 is not stepped down via a secondary winding but rather is
connected via C2 to the base of Q2. This means that at resonance, Q1's collector
load is a resistance of at least 10 k

. This higher load resistance at the collector of Ql provides more overall gain in the
circuit for oscillation.. However, because the collector of Q1 is sensitive to stray
capacitance that will shift the oscillation frequency, the output signal from the

oscillator is taken from the emitter of Q2, a lower-resistance point. Any small stray
capacitance loading into the emitter of Q2 does not cause the oscillator's frequency
to shift.