New-York tribune., 1922-06-25
How to Build Transformers

ogesnon-i. When go, volts afs 49,
Piled ~ 'hc primary n an auiio frequency
trarsfofmsr what 10 ne toi'szc ln tho
secondary 2 what T. The ratio between
,h- primary sni no secondary - these
trLfsfofmefs7 Does 10 diner IN the
iransformer tsir.sn thr dsiecior snd the
hrs, smpilfyinr tube and those tfshsform-
srs rhich afs placed between ths smpiify-
inr tube, aioref what &. the ourren,
in ue pate circuit ~ radio Frequency
tubss de'ecior 'ubss snd aadlo.frsQuency
ampllf' ine tubes, 8 How can make an
asdio .ffeqeeney 'rsn.fornsr' How can
make rsdio.ffequsney ,fsns'orm.r .
" H O.
Answer + The voltage in the sec
ondary Of the transformer will depend
upor the ratio that exists between the
primary and the secondary. This ques-
ton canno; be answered unless The rs-
ito Is known. ?. Tha, varies in differ
ont cases The usual IL 3:i. 3. For
audi1 frequency they are all the same.
I. The plate current IN the radio frc-
qucrcy. detector and audio smplifcrs
will depend upon great many factors
and A. they are not stated The answer
eanot be given As = general approxi-
nation. however, IL will be IN the neigh
borhood Of from three n four mill
nmperes 5. In connection with The con
struction Of audio.frequoney trans
formers these should be wound on a
's.inch core The core itself Is made
UP Of lamina'ed iron IN the form Of an
oblong with a center section dividing
the oblonr into two squares. The pri-
mary will be laid upon the center see
tion and will consist 81 100 turns of
No. 6 enamel covered wire. The pri-
mary mus, bc 80 wound that there Is 4
layer Of very fine paraiin-impregnatcd
paper around each layer. The sec
ondary viii consist Of 10000 turns Of
so. ii onamol-eovercd wiro. with each
layer insulated in the same manner rs
above When the windings are COM
pls.cd thc primary should have a direct
eutrent resistance of l.075 ohms and
the secondary should haze a direct
curren. resistance - i.7C0 ohms. The
ratio o. this transformer will be 20 l.
In other words. the secondary will havo
n voltage Of 67is where 22'4 arc
applied on tho plate circuit. q. As !
have stated repeatedly in this depart
men'. in my opinion radio-frcquency
amplihcation b. means Of the step-by-
step system. OF cascade coupling, "a
still in an experimental stage 50 far
~ shorl-Wavo reception B. concerned
No real satisfactory transformer has
been evolved ne yet. In my opinion. The
trouble does not lie so much with t1f
trhnaformcr alone as ~ does With the
tran7forncr and vacuum tube com
bined. u must be understood that tne
vacuum tube has the property of ca
pacily between i's elements and thi'
property has very definite. specific
value. which materially affects The cir
cult, despite tho fact that tho capacity
is measured In micro microfarads
With vacuum tubes being turned on
on production basis IL Is absolutely
impossible 20 get two tubes that are
exactly alike in their capacity. and thil
+ very serious problem when IL T.
considered that tho value Of tho ch
paciiy is 80 very lo~. The result II
that In practice tho radio.frequency
transformer that may he somewhat
successful with a certain particular
tube is absolutely unreliable when d
different tube is placed in The Circuit,
due % the reasons given above. Under
the circumstance. therefore. ! would
not advise its use. except for cvperi
mental purposes ~ this time In vieV
Of the remarkable results that have
been obtained in Major Armstrong.
new system. which is tho real. true
form Of radio frequency amplifcaiior
on short waves. ! should rather you
would wait until the constants for TIN.
system are released ard then expert
ment with them. In my case Nh,
transformer must be wound special,
for the wave length you desire 20 re-
eeive.