New-York tribune., 1922-09-03
Frequency
And Crystal
One Stage Radio Frequency
Used to Anlplify Incoming
Wave Before Detection
Is Made With Crystal
only One Stage Succeeds
l,ircuit Simple 10 Operate
and Is Very seIeciive,
Also Steady in Results

iector ne uSeQ 4ot d.
,,a.,c ana entertainment after the m
ror;n~ wave has been subjected 20
b;oh frequency ampliheasiony 70 s0iSe
This question sesies of extensive eN-
ne,;paents were conducted during 'As
week IN our new laboratory
The results Of these tests emphasize
80 !, can he done successfully with
4 limitations. So far we have no'
.n abIe 10 obtain success with more
Nm one stage of radio frequency
-,;ssat;on ahead OF the crystal. AL
ass.p. a.pp.sass 10 eo beyond ono stage nave
sNs'ud .',.sd in material reduction OF
signal strength.
ordsr to approximate the most
a.as.s sonditions the test was made
...ss single wire indoor aerial, con
.;ss;se Of Fifty feet of No. i8 cottor
sssAyed annunciator wire. This wire
ssss stretched in a room on the fifteentf
ar ~ steel-construetion building
.ssays ,s,ss the worst shielding effect is met
llnr;no fhe experiments first one stage
= ra5jo frequency amplifieaton was
smoloyed, then two, and finally three
stages.
Circuit Made Simple
+, order to reduce the circuit to IT'S
.;rn,ast form the tuning element IN
~ aerial consisted Of an ordinary
s.sndard short~waye variemeter Gil
ssftly connected to the aerial ana
aro,,nd The amplifying tubes were of
az Tv 20l type, and the high fre-
,na nnsncv transformers Of the r. I. |
type s.a 4,,a+ +be
etycuit was particularly steady so Tong
a. No more than one stage was em-
+ sIoysd. and moreover it was very Sc
ioct;ye far more so than in the ease
of the ordinary crystal set using g
soahle timing circuit. In fact, it was
80 sa)ectjvc that the slightest turn OF
ibe yarjometer rotor threw out the
brasdeastinc station, and as conse-
n,enca IL was found advisable. to use
veynier attachment on the dial OF
Tho variometer in order to make
miuute adjustment Of it. Interference
from wireless telegraph stations was
al q minimum.
pctentiometer Is Necessary
The circuit is held in stability by a
uotentiometer. which should have di-
rect current resistance of at least zoo
obms II will be found that in opera
tion the best results are obtained with
the potentiometer pointer almost COM
pletely over to the negative side. A
fxed condenser of .002 MID. capacity
shunted across this side of the po-
sentiometer is necessary as bypass
for the high-freauency currents.
Transformer
The crystal detector is Joined di-
reetly across the secondary OF the
radio frequency transformer with the
talsuhone in series in the usual man
ner Ii was found that sufficient en-
ergy was obtained from the output Of
the transformer to operate any type OF
crystal detector, and consequently 1t
ID strongly recommended that de-
.ector Of a more rugged type than
galena be employed in order to reduce
the necessity of frequent adjustments
II the catswhisker Silicon or iron
pyrites were found to be excellent de-
teetors.
AS a rectifier the crystal detector is
quite on a par with the vacuum tube,
and it has advantages not enjoyed by
the vacuum tube, in that it is com
pietelv noiseless in it's own operation,
and the consequence is that the repro
ducsion in the telephones is very
sweet and clear
Second Stage Fails
n the experiments in the laboratory
Ii was found that the addition OF a
second stare reduced the efficiency OF
the entire set and, as a matter OF tact,
the output as reproduced in the tele-
phones was not as strong as from one
stage. It was found that the crystal
detectoF would stand fair amount OF
ordinary vibration without losing It's
sensitive snot OF course, deliberate
shaek would throw it out OF adjust
meHt.
This circuit is extremely simple to
operate There are but two adjust
ments to make after the flament cur
rent has been turned on to the proper
degree It will be found that the tube
operates best when it is slightly more
brilliant than in the normal receiving
sets that do not employ radio frequen-
cy anpiihcation.
The two adjustments are the vari-
ometer in the aerial circuit and the
potentiometer. AS a matter of fact,
onee tho potentiometer has been set a
slight adjustment of the variometer
Nih tune the circuit to different sta
sipns
Will Not Eliminate Static
While this circuit eliminates inter
iererce from other stations to very
marked degree, it does not, of course,
ehfnlnate static. However, static in
erierenee is not quite as bad as that
+ experienced with a detector, and two
ton.
The complete equipment for this cir
salt IS the aerial and ground connec-
oh' In the event that an indoor
ssfiai is used lightning arresters are
soE necessary. One standard short
y. saSe yariometer, one vacuum tube, Nv
~ with socket and rheostat, one 200
vam potentiometer, one fixed conden-
~ '0G2 mid. capacity, one 6 volt bat
~, and "Bn batteries giving d total
s.sage OF 45, one crystal detector, one
geir OF telephones and one radio fire.
gseasy Transformer.
Il experiments are now being made for
w PURPOSE of joining two stages OF
@ @1uso frequency amplification to the
,ssspnt from the crystal detector SO
sat the music can be rerroduced on
KS KS ioaa speaker. As soon as this has
80 successfully achieved detailed
sss assembling the circuit and ap-
sstatus viii be given.
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uoiiand 10 Use Radio
he Hnffy.,,.l