Page 102 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

RF amplifier. Also the leads of the secondary may have to be reversed. Refer to the

note at the end of this chapter.
Figure 7-1 presents a "sketch" of a possible transistorized regenerative radio.

1
~ Secondary
L
r----------->l......,
RF Amlplifier Q1/Q2 r---
RF Antenna Filter

L 1-VC1
Power Det Q2
Audio Out

Gai n Control VR1

• L 1 Secondary T1 Audio Out
C
to 10 Turns +3 C3
.01 uf

~ ___ ~~ __ ~2~ 01 Audio Transformer JI""f?
MPSH10
• L 1 Primary
VC1 RF 4t-------=2'----i 02
100 Turns
MPSH10

+ 1.6 ref

R2
, l VR1
2K
C2
Olu

100K

FIGURE 7-1 Block diagram: and schematic of a "possible" design for a
regenerative radio.

In the figure, the primary of antenna coil Ll is connected to an RF amplifier circuit
consisting of Ql and Q2. Ql is an emitter follower amplifier designed to give
near-unity gain while also providing a high-impedance input resistance for Ll's
primary, which will not load down or degrade the Q of the antenna coil. The
secondary of Ll, which has a smaller number of turns compared with the primary
of Ll, is used differently in tunable radio-frequency (TRF) radios and reflex radios.