Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1922-04-30
Ky Fred lSOnsIov

by Fred koHslOw.
IN the midst of what Is described
Dy experts as "wIrelcss craze"
low OF tho dcvotecs OF the new art
OK radio communication consider the
study or their new sport In the least
necessary to it's enjoyment. While II
Is. perhaps. true that n knowledge
or the intricacics OF the science Is
not essential to the enjoyment Of
q radlo concert. there VIII develop
betore tho studcnt of the science un-
Il toid possibilities by ways OF results.
10 say nothing OF the fascination of
ono or the most interesting sciences
known. with acquaintance with the
art.
Tho art OF radio communication as
~ STANDS today centcrs about "A tiny
.. hulb or glass very similar TO the
electric light bulb by which you
rcad. Were II not for the inven-
lion OF this delicate and sensational
instrument. wireless communication
could never have assumed the i'm.
portant Significance to the CONNER
ciai world nor It's popular signif-
canoe TO the ordinary pleasure
ing American.
i Without going into the details Of
invention. stretching over surprislnY-
~ Few years, the vacuum tube Is a
product Of some score OF scientists.
each contributing an important item
To Its development Lee DeEorest
probably did moro than any single
man to make the vacuum tube what
4 at Is today. our own Thomas Edi-
son-though few people realize 1T
discovered the basic principle OF It's
operation
First Tube Simple.
Tho FIRST vacuum tube. or. more
properly, elcctrOn relay. was a very
simple and inefficient piece OF APP
paratus. II WAS merely an cvaCu-
ated glass bulb containing Dracti-
cnlly the same sort OF flamcnt. or
incandesccnt wire, found in the or
fdinary electric High, bulb. and
small metal plate separated a short
1 distance from the hlamcnt.
This tube operated as Il simple re-
4 lay for electric waves on a principle
essentially as follows: 1t was known
that the small tungsten wire. or fla
mcnt. heated to incandesccncc In the
vacuum, gives OF free particles OF
negative electricity, or clcctrons.
whose diameter IL less than one
trillionth OF an inch and whose We
locity within the tube sometimes at
| talns a speed of 10000 miles per sec
ond. This operation liz based upon
the theory that AL substances con
huc,ivc OF electricity contain these
ciectrons existing In a free state.
and THAI merely the heat OF vaporiza-
ton Is necessary 70 separate them
''pl' Aii'!i pcs1NlpHS
when they were thus separated.
tho metal plate. constantly charged
with positive electricity. with the aid
OF simple dry cell such as rings
your door bell, attracts IN. free cleo
irons TO tho plate and thereby set
M a now OF electricity la the cir
cult from hlamcnt 10 plate. plate TO
battery and battery 20 :ilamcnt again.
The hamcnt was kept inca ndcscent
with another battery.
Present Vacuum Tube Young.
In 1907 the real vacuum tube "as
invented by inserting thin coil Of
wire between the hlamcnt and plate.
called Il grid. 1t WAS then that the
real vacuum tube came into being
AT the present time the operation or
this tube is divided. for convenience,
into three major parts according 10
The three biz uses 10 which IL IL
put. The vacuum tube, or clcctron
relay. is used as dctcctor Of wire
less waves. ns an amplitcr OF wire.
less waves and as generator OF
I. high frequency oscillations.
The sinpi. dct.ctor circU!; is brief
~ as follows: y small battery,
known as AN ~ battery. usually OF
some six volts. is connected with a
rhcostat. or variabl. resistance. 80
+ that its inca ndcsccncc can be easily
regulated. The grid is connected 10
the coil OF wire which is set into
oscillation by the induction OF the
antenna current. In other words,
radio wave impinging upon tho an
tcnna sets up an osSillating current
in tho antcnna system. passing
through coil. or inductancc, known
as the primary of the transformer.
which. in turn. sets IN similar
ycurrcnt in the secondary coil. located
close TO the primary.
with one end OF this secondary coil
connected TO the grid OF the vacuum
tube and the other end connected TO
tho filamcnt OF the tube. the an,cnna
circuit is completed. The plate Is
then connected to the positive termi-
nal of a "R" battery. of about TWEEN
u volts: the battery negative tcrmi-
nal connected to a pair OF phones and
the phones connected to the niamcnt
of the tube. To obtain clear idea
OF this connection, II Is suggested
that the student draw diagram best
isuitcd to his Idea OF the individual
clements.
It would seem that. provided the
brilliancc of the flamcnt be main
tanned, the application of more and
more voltage. or electrical pressure,
to the plate would produce more and
more current. In direct ratio. flowing
from this filament to the plate. This
IS in accordance with what is known
as Ohm's law; that. provided the re-
sistance is equal, the pressure dOu
= bled doubles the quantity of current
flowing In the circuit. However. this
Is by no means true in the present
case.
Theory OF Operation.
1t will be found that. for a short
time. a gradual increase in the cleo
trical pressure cxcrtcd between the
flamcnt and plate will cause an al
most proportional increase in the
amount of current flowing across the
terminals. Then, suddenly. a slight
increase In electrical pressure will
cause very large volumn OF cur
. rent to cross the clectron circuit.
This continues for very short
time. as the pressure IS incpcased.
until the process revcrscs itself; the
top of the curve becomes fiat. En-
gineers plot this condition on graph
paper and call It the characteristic
curve" OF the clectron relay.
Now this. in brief. Ia what occurs
between the filament and plate, we
have learned that, at certain points
OF plate pressure. a very small cleo
trical pressure will cause very
large amount Of current to flow in
tho circuit and, since the phones are
In this circuit, the effect Will be de-
cidedly appreciable In an audible
g..