The Challis messenger. (Challis, Idaho) 1912-current, 1925-06-24
Five Principles
Governing Radio
Explanation Will Enable
All to Understand OPP
Grafton of Circuits.

There are many processes which
take place In a radio receiver that
enable an operator TO tune In the broad
cast concerts. Numerous changes take
place In the radio current from the
time 1t enters the receiver from the
aerial until 1t leaves on Its way to
the headphones. but II these changes
are considered step by step. they do
not appear complicated !
The FIVE important principles on
which modern radio circuits are based
are radio frequency application, de-
lection, regeneration, reflex amplifica-
ton and audio frequency application
An explanation of these five principles
will enable person to understand the
operation Of any radio circuit. Every
circuit makes use Of one or more Of
them.
Consider the difference between ra-
dio frequency currents and audio fire.
that flow into a receiving set from
the aerial are in the form of an alter
mating current that is, they are in the
form of a current which rapidly re-
verses in direction of flow, just like
a clock pendulum swings back and
forth, except that it changes many
thousands of times more often than
the clock pendulum in a given period
OF time. An alternating current in
which the reversals, or. alterations,
occur at a rate of from twenty to
twenty thousand times per second. will
cause a set Of headphones or a loud
speaker to emit an audible sound
when passed through it. Currents re-
versing at such rates or frequencies
are called "audio frequency currents"
Radio Current.
The radio current, however, that
comes into a receiving set from the
aerial changes In direction much more.
rapidly. The signals received from an
ordinary broadcasting station are Of a
frequency of from $4,000 TO 100000
reyersals, or cycles, per second. These
currents are Of frequencies much too
high to create a sound when passed
headphones or a loud speaker,
and to distinguish them from audio
they are called radio fire.
quency currents
A radio receiving set must perform
three functions. 1t has to tune to the
station wanted, it has to
modify the received radio frequency
current in some way so that it has the
effect of audio frequencies and Is able
to operate headphones or a loud
speaker, and in the majority of cases
1t has to amplify the received current
so that the volume of sound Is suffi-
GENTLY great. The tuning function Is
not directly concerned with the
changes that take place in the radio
current within the receiver.
Changing the radio frequency cur
rent SO that 1t will operate headphones
Dr. a loud speaker is accomplished by
1 vacuum tube called the "detector
.ube.' After the radio frequency cur
rent has passed through the detector
lube it behaves, for all practical pur-
poses, like an audio frequency current
Amplification.
Some amplification takes place with
u the detector tube in the process of
detection But an application many
lines as great may be obtained by run
ling the current back through the de-
ector tube again. employing the sys-
EN- known as Regeneration" This
system makes one tube
let as both detector and an amplifler,
md in that way enables one tube to do
he work of two.
When it is desired to get a still
,reater volume of sound from the
or loud speaker, the cur
ent in the radio receiver is further
Implified by passing 1t through one or
more additional vacuum tubes, used as
mplifiers. II the radio frequency cur
ent is amQlifled before it reaches the
letector, by passing it through an am
'lifier tube, the process is known as
radio frequency application" If the
udio frequency current after leaving
he detector tube Is amplified by pass
ng through one or more additional
ubes, the process is known as "audio
application. New York
lines.