Evening star., 1923-05-13
BY PAUL GRIGGS.

Contrary to the popular conception
the detector tube does not aggressive
ly reach out into space. figuratively
speaking, to capture passing signal
waves.
On the contrary. forces from the
passing waves actually Invade" the
tube, and these forces impose their
will, so to speak. on the tubes "elec-
tron inhabitants"
The tube. when functioning as a
detector. may be likened to a region
wherein numerically strong army
of electron soldiers are always active
Normally. they are always on the
march. over a designated route, under
the influence of the tubes own po-
tential or voltage force. but their
normal movements are interfered
with periodically by other potential
forces which invade the tube.
The tubes own electron- potential
energy Is very much greater. COM
parattvely. than the potential energy
which invades the tube. Yet the
peculiar nature of the influence OF
the latter over the former is such
that the weaker invading forces are
enabled to exercise almost absolute
control over the stronger normal
forces of the tube
Arouse Normal Energy Forces.
AS a result, the invading forces not
only control and direct the tubes
normal energy forces for the purpose
OF manifesting their presence and
causing their equivalents to be re-
produced in the form of human
speech. music and other sounds. but
they also compel the tubes normal
energy forces to actually reinforce
or strengthen these manifestations.
The tubes functioninG, then. or the
actions which take place within the
tube and the tube circuits when it is
operating as a detector. is entirely
dependent on two distinctive sources
of energy-the tubes own electron-
potential energy and the compare
lively weaker. though dominating.
alien" potential energy which leaves
passing ether waves and enters the
tube.
With this preliminary outline, an
attempt will now be made to describe
In technical language the func-
tioning of tube as rectifer of
alternating electro-mag gnetic energy
or detector of radio waves as fore
cast in my article of April 90
Let us produce the electron army,
or the electron- potential energy, in
the tube and its circuits, meanwhile
dlSconnecting the receiver from the
antenna so that there will be no in
yasfons of allen potential energy
from passing waves for the time
being.
We bring the dormant tube TO life
ana cause it to produce electrons by
circulating an electrical heating cur
rent from the filament battery through
the tubes filament or negative cleo
trode. We then start the electron
army on the march under the infiu-
ence of the tubes own potential force
by connecting the tubes positive
eiectrode or plate to the positive ter
minal of the plate battery and con-
Meeting the plate battery negative
terminal to the positive terminal of
the filament.
Move In Constant Stream.
Under these conditions the swarms
or electrons within the glass bulb of
the tube will move in constant
stream from the negative filament
electrode through the vacuous space
to the positive plate electrode thereby
causing continuous unvarying cur
IN one direction in the plate circuit
The plate circuit is known as the
output" circuit of the tube It is
the circuit with which the head
phones or loud speaker windings are
connected in series so that the cur
rent of electrical energy which cir
culates in one direction in this circuit
Will now through these windings AS
long as continuous unvarying cur
rent circulates through the plate cir
cunt, including. the headphone or loud
speaker Wtndings. there will be no
response in the telephones. because
this current must be changed from
us unVarylng state to a varying or
pulsatinS current in order to vary
tne magnetic properties of the tele-
phohes and cause the telephone dia-
phraSm to vibrate, thereby creating
corresponding sound waves
IL IS the potential forces which leave
passing waves and invade the tube
that change the tubes normal un-
varying current in the plate or ont
put circuit into varying or pulsating
current, which in turn cause the tele-
phones to create sound waves of the
invading. potential forces equivalents.
The plate or output circuit of the
tuoe consists of the plate or positive
electrode within the tube, the lead to
the plate battery. the battery itself,
the lead to the telephones. the teIe
phone windings. the lead to the posi-
tive terminal Of the fllament, the fla
ment electrode within the tube, and
Hlament from the plate within the
tube. e
Radio Frequency Component.
A condenser is shunted across the
telephone windings in the plate cir
cult because the varying current
which circulates in the plate circuit
after 1t has come under the influence
of incoming signal wave potentials
is the sum of a radio frequency cur
rent and OF the tubes constant cur
rent. The radio frequency com
ponent cannot circulate through the
telephone windings and passes
through the condenser, the constant
pulsating current cannot pass through
the condenser and circulates through
the telephone windings.
Gu cult of the tube, let us now consider
Inc critical part Of the input cir
cult is the grid or Controlling"
electrode of the tube. It is frequently
compared to the trigger of a gun and
the whole detector tube action COM
pared to gun being fired, reloaded
and again fired thousands of times
within each second of time.
The grid electrode is always placed
between the filament and plate in the
bulb, directly in the path of the cleo
irons.
By applying very slight potential
variations to the grid ho al