New-York tribune., 1922-06-11
Condenser Is
Important in
Radio Sets
Has the Quality of Capacity
Which Is Determined by
Size of Plates: Thickness
and Nature of Diclectric
Offers Easy Path for A. c.
Fans Warned Not to Judge
Value Of Condenser by
the Number Of Iis Plates

There is no individual piece Of appa-
rntus in radio circuits that has 50 many
varied uses a. the condenser. and il
i'. in all probability. the lens, under
stood instrument in the set by the
average user.
The condenser is divided into two
distinct types. each Of which has a
specific purpose They are; the fixed
type and tho variable type. In reeeiv-
ing circuits. the former invariably con-
sists Of successive layers Of tinfoil and
specially prepared wax paper. The tin
foil forms the plates ~ the condenser,
and the paper is the dieicctrie or insu-
lnting material.
The variable type Of condenser con-
sisis of two sets Of metal plates which.
IN the majority ~ cases. consists of
aluminium, 20 arranged that one SCI Of
plates is stationary and the other set
moves IN and out Of the stationary
set In this type of condenser. air is
generally used a. the dielectric.
Warning to Radio Fans
OF condenser. this warning 20 radio
fans is very timely: Owing 20 the tre-
mendcus expansion Of interest IN the
radiophone. broadeasting condensers
have become classified by the number
Of plates that they contain. A large
number o. "Ay- -by-night" manufacturer
have entered this profitable field and
arc turning out condensers on this
basis. The number Of plates. however
is no indication Of the value or eapac-
ity OF n condenser and this fact should
be borne in mind by the radio fan when
he Is making his purchases. rs Will
be shown later on.
A condenser has the electrical prop.
crty known as capacity" Like al
other electrical properties. this i'
measured by a certain standard which
is known By the name "farad.' In
other words. "farsd" is the basic Unit
Of measurement Of capacity in an elee-
tric circuit. and the name was gwen
in honor Of Michael Faraday o;
the electrical pioneers.
Basic Unit ia Too Large
Now for all practical purposes. the
farad Is far too large = measurement
|
that II is divided into milliouth parts
which are known az "microfarads.
or. using the common abbrcviaiion
"nfd": thus. condenser is said 20
have n capacity Of .o05 mfds.
The determining factors governing
the amount Of capacity in the conden'
ser depend unon the area OF the plates
themselves in the FIRST place, and, sec
ondlv. the nature and thickness or the
dielectric between them. For instance
in variable condenser, using air as
a dieleetrie, the capacity Of the con-
denser will depend upon the distance
which separates the different plates
from each other. This can be clearly
seen when IL Is pointed out that the
clnser the plates are together, the
thinner is the volume o. air between
thcm; and consequently the greater
will be the capacity Of the condenser.
Correspondingiy. the further apart tne
mates are. the lower Will be the
capacity.
From this it will be seen that since
the capacitv Of the condenser depend,
upon the area Of the plates, a. wei
as the thickness and nature OF ne
dielectric. rating a condenser simply
by the number o. plates u contains ls
not a true indication Of rs value IN
the circuit The only indication tnai
can be correctly obtained IS by nc
actual size Of the plates themselves.
Variable cOndensers are used ~ INC
oscillating circuits Of a radio receiver ;
or. 10 put 10 IN another way. m the
wireless circuits o. the apparatus. lhey
are made variable IN order ihot inc
amount Of capacity IN these circuit
can be adjusted. 80 that the circul'
itself can be placed into resonance
with the wave length Of the !neominS =
signals.
Condenser Can BE Charged
Now the condenser has a very
neculiar propcrty. n can be charged
up and discharged. When the current
is applied 70 the circuit IN which Q
condenser Is placed the condenser VIII
store I'D q charge of electricity on rs
dici.c.ric. up 10 the limit Of rs
espacity. In the case OF direct cur
rent. the current will flow up 20 tne
time that the condenser Is charged
after which there will be no further
passage Of the current.
With alternating current, hoWeFtI
We have a different situation entirely
The current. first Of all. charges me
condenser with positive electricity ana
Immediately reverses this charge win
the alienation Of. the current iiseii
Consequently the condenser offers q
froe path for the passage Of aliernAi.-
ing currents. The facility with wn'ch
these currents will pass through q con-
denser depends entirely upon the ire
auency. Therefore. the higher TOE
frequency. the more easily WI the
currents pass through the condenser.
As We arc dealing with frequencies
in excess Of $4,000 cycles second
50 far as wireless is concerned, II
will be seen that a condenser Is thus
enabled TO perform very important
function in the wireless circuit, as u
offers very easy path 20 the pas
sage Of these currents.
This is particularly important "neh
IL is taken into consideration that the
induetsnee in the oscifAting circuit
has the same property, electrically
speaking, as momentum and iner'
ia" in mechanics. In other words ne
inductance in an electrical circuit
tends 20 resist any change In the dir.e-
tion and flov Of current, while the
condenser assists the change.