Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1922-07-09
CRYSTAL DETECTOR
SIMPLEST RECEIVER
Expert Gives Theory and
Operation of Fundnmeu.
tai Radio Sci.
KECrIFIES RADIO CURRENTS
Ch~cfuily Arranged Circuit of Ut
most Importance In Efficient re
rri,inx With Outnt-CrystnI SrnsI-
uNit! Eovrrns l.Oudncss Of signals.
HEcrlriEs RADIO CURRENTS
Ivy Paul r. G;odlry,


"rnilaicrai conduc,ivity" What is
Iitr
IT is the secret OF the crystal set.
/; is the property that makes OF any
/ substance a 'detect"r" OF radio sig
nails
Certain minerals. and few other
materials. posses the characteristics
which make them good conductors
for current PASSED through them in
one direction only. For example. u
piece Of carborundum may show
resistance OF only TWO or three ohms
TO certain current. When the cur
rent Is reversed. III. resistance to It's
dow is several hundred and in some
Instances, several thousand ohms.
When substances possess. these
characteristics az" placed in q cir
cult where an alternating current is
Towing pulses OF one polarity pass
with ease. while those "r the other
are wasted and lost. The substance
thus becomes known as 'rectificr."
since Il "r"ciitcS' the alternating
current, leaving In It's stead. a pull
sat!ns. und!rrCtionn! current
Need OF Rrstinrrs.
radio work are essentially direct cur
rent machines thus the necessity
Tor rectifer--or as they are always.
called detector. in the radio re-
Cefver
Some minerals used rs detec,ors
are SO sensitive that tho currents
fcd> 10 the magnetic telephones are
much lareer than can he accounted
Tor by one-half Of IN. incoming sig
nal currents alone. one explanation
OF this is that the wasted half OF the
current produces heat because of
the resistance or the crystal. This
neat is produced al the point of con-
tact OF crystal with the "feeler"
wire.
Under certain conditions when two
unlike substances are in contact. the
'Pp!lcation of heat Will produce :,
now of electricity. y combination of
TWO dissimilar substances for the
production of electricity in this way
Is known as 'th-rmo. couple
Doubtless. some types OF galena
dead ore and ono or two similar
crystal. not only show unilatcral
conductiNely, but also act as therma,
batteries. giving OF pulse of cur
rent each time as result OF other
heat-producing pulses which pass
through IL.
Arrangement.
1t Is important to arrange III.
crystal detcctor so that all of me
energy which is collected in its cir
cnl, passes through II This is ac-
complished by making sure that
thcr" is nothing connected across
tint detector which could act as
small condenser
II small ondenscrs are formed tv
IA ."msth Of twisted pair" conduc-
tors or large metal surfaces which
are closely adjacent 10 each other
aud used in the connection or CON
Siruci!on Of the crystal detector sys-
ten. they Will AFFORD low resistance
paths FOR tn" high frequency cur
rents.
Currents flowing through these
paths VIII never be- rectincd and so
Ear - the magnetic telephones are
concerned. VIII s"rvc 40 purpose
In the hook up" OF a crysta, de-
i"ctor circuit the leads should never
%" allowed 70 form pair" As
such they would act as small CON
dcnser. They should be single con-
duc'ors. spaced somewhat.