Page 110 - Build Your Own Transistor Radios a Hobbyists Guide to High-Performance and Low-Powered Radio Circuits

secondary winding of Ll in a variable manner. This variable signal current into the

secondary winding allows for good control of the regeneration. For example, if the
wiper of VRl is set toward pin 3 of VR1, most of the regeneration signal current will
be diverted to the secondary of L1. However, if the wiper of VRl is set toward pin 1
of VR1, most of the regeneration signal will be diverted to the +3-volts supply,
leaving little or no signall current to the secondary winding. And setting the wiper of
VRl in between will send a fraction of the regeneration signal to the secondary
winding and a fraction of this regeneration signal to the +3-volts supply.

Note that the +3-volts supply is also an AC signal ground. That is, other than
having +3 volts DC, the +3-volts rail has no AC signals on it because AC-wise, it is
the same as ground. Also note that Q2 now is a fixed-gain amplifier and does not
have a variable reSistor, as seen in Figure 7-4.

It should be noted that in the prototype, VRl is a multiturn potentiometer. The
audio signal from T1 may be amplified further by using the Q3 amplifier circuit from
Figure 7-4.