Natural Radio signals occur within the range of human nearing so no
frequency conversion or demodulation is necessary. All that is necessary is to
amplify the signal and convert it from a radio wave to audio so that it can be
heard. At its simplest, a Natural Radio receiver is a high-gain audio amplifier
with an antenna on the input and headphones or a speaker on the output.
( There are naturally occurring signals that extend above and especially
below the range of human hearing, but the most common signals are within the
range of our hearing.)
The only real complexity that need be added to a receiver is some form of
filtering to get rid of the annoying hum and buzz from power mains that plagues
the Natural Radio listener.
Receivers are of two basic types: E-Field and H-Field.
Another source for boards of interest to the VLF and Natural Radio
experimenter is Far Circuits. Far Circuits has produced circuit boards over the
years for many construction projects appearing in QST, 73, and other
electronics publications.
The listing on the website for each project board includes the magazine and
issue where the article was published, but there is really no other description
of the project other than the title. Therefore, it might take a little research
to find out the details of the project. You can order reprints of the article
with the board for an additional $1.50.
It's worth spending some time looking through the listings, as having a
circuit board makes construction a homebrew project much easier. Looking at
this list is also an easy way to find a reference for project you may have read about a few years ago, but can't remember where you saw it. Here
are some of the projects I found that might appeal to Natural Radio
Experimenters:
VLF SPACE SHUTTLE RECEIVER
JOE CARR VLF RECEIVER
GYRATOR RECEIVER
A SIMPLE 10MHZ WWV RECEIVER BY
MCKEAN
REMOTE TUNED ACTIVE ANTENNA/CORNELL
(2 BD SET)
CORNELL WIDE BAND RECEIVER
AMPLIFIER
CORNELL REGEN RECEIVER PREAMP
AAVSO VLF RECEIVER PREAMP BY CARR
AAVSO RECEIVER BY CARR
There are also some audio amplifier boards that could be used as the headphone amp for a Natural Radio Receiver. If you are considering building a beacon transmitter, there are projects for automatic keyers and oscillators.
Equipment & Software 
