Palmer's Regenerative Receiver No. 1
Here is the culmination of my first regenerative receiver. I just
used a typical Armstrong circuit, which is the introduction of feedback
via the 'tickler' coil.
Varying the potentiometer will vary the power to
the transistor, which provides a control for the gain. Alternatively,
the capacitor connecting between the tickler coil and ground may be
varied to adjust regeneration. Or you can simply move the tickler coil
nearer or farther from the tank circuit to vary the gain.
The tickler coil need not be much more than a quarter of the turns
you wind for the main inductor, and a 10-60pF variable out to do for its
The resistor and capacitor connected in series with the base serves
as the venerable "gride leak" detector, providing the transistor enough
bias to detect signals. The 10 ohm emitter resistance helps increase the
input impedance to the transistor.
The receiver can be coupled to a RF amplifier and audio amplifier,
which is what I did in my actual construction. I used a simple 1-stage
and then a 2-stage audio amplifier
that was capable of driving
low-impendance headphones or loudspeakers. Note that if you put a capacitor across the 1k resistor in that
audio amplifier, you can greatly increase its gain, if need be. If you don't want to use an
amplifier, high impedance headphones, such as the ceramic earpieces you can
get from Radio Shack, will work nicely as well.
Overall the performance is good. Careful adjustment of the feedback
coil and gain control yield selective tuning and enough sensitivity to make
stations quite loud. Reception of amateur radio stations is even possible on
occasion. So far I've received WWV, Radio Habana, the Voice of Russia, WLO, and
WWCR amongst many other stations.
Here are some views of the completed project. I used simple point-to-point
construction on a wooden base, using nails for soldering posts. Not to shabby,