ELECTRONICS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600200033-4
• Release Decision: RIPPUB
• Original Classification: R
• Document Page Count: 14
• Document Creation Date: December 22, 2016
• Document Release Date: June 29, 2011
• Sequence Number: 33
• Publication Date: May 21, 1943
• Content Type: REPORT

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CENTRAL INTELLIGENCE AGENCY
IN FOR rat 1 1-R'1i
COUNTRY USSR
SUBJECT E1sotronice
PLACE USSR
ACQUIRED
DATE ( ;Marob' 1947
IfiP ION
fives aOWlAai cowruas /amaw.t is Mlaala0lua aA7/Oadt 00r_Tt.II
W two warp. sta7is avuew eat waaax.o or sa unoun a acr ro
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7j.O. 0a/Od'd/dMN eawtuKaw IN WIN. us .7aa WT a? amA{a0
1M bapaaq waAaaawr R us awr.irla0 a4067.
REPORT
DATE DISTR. 21 May 1943
NCB. OF PAGES 14
NO. OF ENCLS.
LUSTED BEIA'M
SUPPLEMENT TO
REPORT NO.
THIS IS UNEVALUATED INFORMATION FOR THE RESEARCH
USE OF TRAINED INTELLIGENCE ANALYSTS
SOURCE Russian periodical pg4 ctckmilca. fro 3, 1947. (FDB Per Abe 677.0 -
'i'ranalatien specifically requeeted.)
m31O S YU L 'i6 Ild A M3I&iufi F41 $-I+AI L L1)DOf,ATI-P t+ t.1
A. T. Lebedev-ifArmanov and A. V. Piearevakiy
Candidates in Technical Sciemeee
ff t;bera in T,macket in the ttxt roer to the Si'oliograph5. Figures
referred to are eppeadedj
tr_ i h per er ti nrmitter car l ornw Plate modulation,
the quality and, to a aotraidsrahie extent, the poorer ebarecteriotics
are governed by' the modulation eye=. R cently, this bee ooneiated of a
multistage push-poll audio-frequency amplifier, the last stage of uhiob
is the modulator, uhieh aorke in a Clues a system =sing very high voltagea
and ourrente in the tubes. The modulation cyst,- embraces a feedback
system ceasiatinC of the primary circuit oY the output or modulation
transfaa~an~.
fits' gwr Lions concerning the theory, the schematic layout, and
ties of the system have already boon dealt. ale p~.WVi,,ale
~ ,. Itn t Nose of regent practical eoork on the cmtr ttion and
regulation of higb-1ovs1 modulation systems, acv of these queations
have rueoived fetter atteaatican. Now problems also arena, neceasitating
the 3etsoduation of a amber of changes is the layout of indilidua1
atsgrs. This article gives a survey of awe of the constractional
preblena t& ; a+>? ry!st-day modal ration system.
It= z
Z JUR Z
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,O'~1fiTR0"1 0."CILVi^sIOY IN M
:rail FCK SUPPRESSION F
RIODAl.oT1.R t3 dRiD CXI U1T
the grid and anode doiu eted together. The LOLal Luca aiaTea+a ... w++o
h
3? The space
modulator tube is shunted with an antidynatronie k note n. The
oaa-ductidty of the konotran is equal to ghe grid-plate p- ...u,R _arA
It therefore followe that this method is irrational.
betasea the grid circuit and the filament of the
cu
a
r
W-133 in Fn ,
ree:etence shunt is required, rrpich greatly increases the cubmudulat..r load.
It is 'spawn that the pr r'ence of a dowavard drop in the dynamic
characteristic curve of the grid current of modulation tubes is the
cause of parasitic ,.iratrot, oscillation. It originates in the dynamic
system, and lasts during that part. of the.voltago-amplifi..cation period
v/men its instantaneous values ran Into the do=ward bend of the curve.
In this case, the frequency of parasitic oscillations is equal to the
futdanentel frequency of the grid circuit which is determined by the
parasitic capacity of the system, the distributed ductanoe, and the
distributed capacity of the submodulotion (arirarj transformer.
To eliminate the.posaibilicy of dynstrnn oscillation it Ras
necessary that the resistance in the modulator grid oixcuf'.t at absolute
resonance frequency vas lean than the equivalent negative s:--.sirtarco of
the space between the grid cireait and the tube filament in the zone of
t._- drop In tahe cn. oa
This race previously achieved by two mot.hodsat
1. The secondary vrnaing of the g atletor transformer was shunted
(in each arm) pith a small active reniate"ee. however, although the drop
in the t'namie characteristic of the grid circuit is comparatively ema11
is extent, it may halo a very large grid to tranaconductonco (for tube
r it reaohss ' - 5 m&-p ). wneoquently, a very low
l
ti
e a ,
connection (i.e., chore ee = eg) is determined .y t
f
~L-5C -E.,,)3=5(i o)L~a--,~DJ'
,sera S DEaC?(F'ao is the driver-Plato voltage).
The oqu.raa.ont tube resistance will be
I _ FZ;
S(its) irk
.1
i.e.a (- t/a) of its internal resistance in the triode connection.
It is nbvioua that the shunt ng affect of the entidynatr sic kono-
t'on 's mast affective?uben the section of greatest tranasonductance of
its. cb&;sateri-5c curve conforms Frith the drrp ir, tray,, mid-current
cbaractoriatic. The kenttron'e rcilaterel conductivity and the limited
value cf its -aetu ration current are favorable factors here, because they
reduce the energy mbicb it requlreb outside the dynetrome one. In
practice, however, the characteristic of The kenatron is much clamor to
the begiuting of the coordinate than is the drop in the modulator+e
grid current, and the latter can be said to correspond to the kcnotron.?.e
satmation mono where the trensconductancs is extromaly small (Fide I).
Ccnsaquasati,y, it rase necessary to increase the filament 5volta s in the
kenotrons and to resort to includinrg several tubes in parallel.
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RED
a
t
a
vw7 lane amplitnnes.(consiueraby exceeding a exc on p
y
uency) Tice use of the ahuart, which greatl
t the i`andemental fre
the ultrasonic Leif, hs:monjac of the grid ourraxut reaching it may have
~ lit+~xie
h it
ti
that if the rescnauz~e r?sistanca,of tits modulator's grid circuit is large,
absence of afilrment. foaover, it rage not possible to use coprer oxide
because the absence of saturation in it reent that the peak of the total
current in the grid circuit ruse sharply raised, and consequently the
load on .,he modulator was increased.
As an antidynatronic measure, S. V. Person ,rropoaed an active loci
resistance shunt, and the inclusion in series with it of a reactance with
a small impedance in the frequency zone of probable oscillation and with a
sufficiently rge impedance in the fundamental band of the amplified
froqueneies Such an arrangement would naturally only be used
whore the resonance frequency of the grid circuit lies outside this
mdamental band. Thus, for examplo, if the resonance frequency lies
beyond its upper limit, a sufficiently small capacitive load would
have to be included in series cith the active shunt roe stance (Figmmre 2)~
It is evident that such an antidyasatronic shunt would not absorb a
large amount, of lover (the further the frequency of possible oscillation
f'rem the amplified band. the smaller it would be). It should be noted
e o
a
on
a
the grid bias den, accoroing to n. (3. Or? ^ M90 9.
by using the?currMt Of one 9_39, for gbctch prd'poao the automatic pY8
Mae crn b I:nalaaded between the plates and the grid (Figure 3b).
In this %z-ep the aatidynetronfc tube's instantaneous voltage vnluo at
,
g
an
(Figure 3e), in cases where a triode is used as, an ant'dynatranic tube,
11 }
bt
ined
b
ti
The efficiency-of the kenotron's antiparasitio action can also be
increased if its characteristic is moved to the right, thus causing it
to operate with the minimum angle of intersection (Figure 1, dotted
claws) . To achieve this, a snpp].enentary negative grid bias, automatic
internal current should be applisd'to the kenotrom's plate
d usin
the stability, of the maculation system's operation.
q
a
lowers the resonance impoesnoe, reduces the danger of aro-ovate and increase.
Similarly, for t tube's totni current uo ge
where Bag a Rgla. (Rg is the automatic grid bias' resistance I
V
r
A comparison of tiri expression with equation (1) shows that t"b
presence of a anpplemental7 grid bias T+~ between the grid and the
plate transfers the equivalent diode's` iferactaristic to a zone of
easeter positive potentials at its plate; the slope of the characteristic
..true is not al . The equation for a family of ideal yid-current
characteristics l can be used in the calculation of the grid bias E.4, t
`jsSt`!t, pk._?,.), (3)
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whoro i p b Yx,, for a conctont ig. The insi,arrh:neova voltage at the
antidynatron tube plate is shorn by.
.e.a E"I Cos Pt uhero 1J and E. are, reat:ectivoly, the excitation amplitude of the
modulator tube, and?ita grid btae. H v5.ng established the value of ea
in equation (3) and considorirg that o = o Rai, , no get a cyatnr; of
two tramacendontal equetionst ::*1 rh..+ch rinc, L oma are Sag and ?g,
cos@r _,,..
IV, F 17
(4)
Here, EIS is rho angle of internoction of the grid-currant impulse;
LL.;, (? j.) is the coofficiont the constant component of this
impaueo. ? The solution of this zyotom of equations can be obtained g aphi-
nquation (3), and consequently also the calculation of Eeg, is true if
r flu; ~,. ,
where FH is the losroat mod ting f, req%ierry.
Only the grid current of the aaudyaatroaio tube, which $a leas than 1/3
of its total current, clown through the grid-bite real tone in t e layout
described above, and therefore this raaistenco must be larger Use ';, _p
when it is included directly in the plate circuit (Figure 3a); aimi_'.srly,
the capacity C can to reduced. The possibility X making a euoww ntial
reduction of t6 eapacit' is one of the edvantages of this layout.
in practice, when constructing a high-level modulation system con-
taining tao 0433 tubes in each era, the most offectivo way to combat
antidynstrorio oscillation is to introduce a capacity-resistance a'aunt
and an ant?dynatranio tube ,rith a eauprlementery grid bias ihto the
circuit lot,oon the grid and the plate. The frequency of dynatron
oscillation 5.,1 this layout ilea in ",Ix- ?0 - 40-to band,
Yoe oaoil1O4ral 5a reprosuntetion of the seodsalatoi'e grid-current
isrspnleaes at different signal levels (i.e., different modulation co-
sffioieents) is abewn in Figure .;a.
The use of a purely active chuit was quite impossible oaring to the
eubsoodulator'a heavy overload. Then using eimb'ie antidynatamic kenotrons,
four B-S-COO tubes (or in a diode cosnsection) with an increased
filament voltage (up to 20-20.5 v) should be =eluded in the arm in order
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* , AancP ona i! lRtson. The Inclusion of a "hunt, formed in each are by a
aortas tore to rthe esistance off 259 ohms and* a capac? ty of 0.C5 , `)erultWd the rotas
M-600 tubes with a filament voltage of 18.5 - 19 v.
The impulse diagram for the total grid current (together with the. oarreat is
the antidynetronto tubed) which coo.-Corms uith this case is shown in Figure kb~
Sveatuslly, when the automatic grid bias circuit (wit", a resistance of 30,000
ohss sad a apacity of b,? F) was included between the Grid and each M-60C tabs,
it was possible to retinae the filament voltage of these tubes to 17 v. The
grid-cement impulse took the form shown in Figure bc.
It ohould be noted that when the gas [sic in the modulator tube is
ignited, a large part of the plate voltage is applied to the grid. An air die-
charger /ic is included in parallel with the space between the grid and the
modulator-tube filament in order,to protect the apparatus. However, in eo=1
operating conditions, the precise regulation of a discharger to DC voltages of
the magnitude of several kilovolts is difficult, and therefore a tube with a,
high electrical stability "hoald be used so an antidynatronio measure. The
electrical stability of the component parts of the grid circuit should ,ot be
lower then the plate supply voltage.
II. PHASE COidPENSATIOM IN A SIA MODULATION TRAN2FOPM818
oust involved :,Lust be reduced as far as posetble~
:_ .u- 1-e.,..f, of the nresent-da' modulation system, the submodulation
? IL to known that in order to ensure a deep and stable feedback over a
broad frequency band, the phase displacement to various ooaponaate of the asr=
nranesurYw)r in oa.v wo.- __ __,?,_ .
also. Considoricg the simplified equivalent otroult )f the transformer and tak-
ht be es-
i
it
g
m
ing auto aocount the leakage inductanes and load oapaoitenoe,
peoted that the subrrodulator would give a reverse phase of 180 degrees. Ia fact,
however, due to the sharply defined effete of resonance peeke to the trane-
former, the resultant phase displacement at.htgh frequencies is considerably in
f thi
s o..w.w...
excess o
of the subaodulattoa transformer can be achieved by the direct coupling of the
-
If the required symmetry of windings to ensured (i.e., the condition where
+ tad ads have the same potenhiai, with rtferenae to the earth), the
low resistance at high frequenoies. This impedance one of course, e p
series with the aombtaed napaoity Co and resistance ro (Figure 5).
ems prsaary aw -------0 --- ----
fern a very high resistance at medium and lo-+ frequencies, tad a correspondingly
b at in
Ftguree 6a and 6b. The following symbols are HOW-
'J- intsraal resistance of the eubmoluletor tubes,
he coniYD0
limiting phase displacement which the subeodulation Lransformor can give ie 90
.egreee (in cases where the reds are o:nse connected it may reach 180 degrees).
However, this layout does permit the use of a well-known phase :ampemaation
effect for the submodulator at certaii frequencies. An equivalent oiroult for
Y.0 iu the mutual impedance between the tranaotraaer'e prteery and; aeooelary
windings,
Z to the load impedance in the secondary winding.
Kirohhoff'e equation for this iajaut is
(Ri f LW~,~ t~([Dfl- ~tWL, -LWMl~,
a
0 Jz,tL- W[})-ij6)LjL_f&)M),
-a,(c:u , iA [~ tW a-[[Ul1) tl3 ,i iWL,tC L1-ztW/~)
0= L M)- (L ? (z
- 5
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in widition, TO calctlCte the voltage at the output t e
fui:l 1c L 'G &i C .: w` i > 'u i : 'r 6,. ..k 3 +Y, rpn -i4f! rj r irr iS1n.
~s l zL~ - M ; the coefficient of transformation
Nli4
In a zone of cuffieiently high audio frectuencieeg there the Imped-
DIICe Z is of the aamo order as the leakage impedance, the ratios -W
0 t-
end can be disregor?cled since they are quantities of another order.
Thus, after a number of modifieetioesu got an equation for the
sub Motor's.frequency characteristic
(6 )
This expression is not true for medium and low froquaneizc.in the
a spectra. For frequencies not excooding 30 - 40 he, the influence
of the iodulatorls full. iapui capacity can be dioregardod, and it may be
ceasideaed that the lewd In the su,:xnodulation transformer's secondary
w +?w A.-- . + far t , nos sFn_w4 1 tn? spec Lin. rpaistanc
d9natronie shunt formed by the capacit7 G2 and the rosistaace'r22
1a"ng established in form%la (6) the valuz.n ) tru' ~ and
z. t Lots., -n
Zo+ twLgj) (Ii z?t~` i
,Zc ro t tI we got the fol'L:,wiog ezproaeion for the frequenoy' o rmeteris+:
E __ r-_''L?Crnr rr:`t a
C,(i-n~+n'(I* ~tLYcC. l+n 7 +
-ai \ y
LVIL +CO.-rw;~,
Ca!! i R. q' A d Y i?~
t~wC~rz~ri C;l'+~
~t~l-~-~-w LsrCx~ I*~*y,
YJK'
As a baeae for this equation, a family of frequency-amplitude and
gra`Macy-pbaee ebarbctariatios rer'o worked out for the folloming %'W-We?-
p use parameters 9
=O.y~i h=u.sy.
The calculation sae made for different ratios 1'a a~d C
The ourvse in Figure 7 1aQ a obtained. 'Ths .flues of the rolevaa~
p?remeteio lie within the limits of gwantities noama1.y fomd in practical
use. In particular, they ae=r Qy a cauaaaiiiP With the aw..vw...8,
R~m975~i Lst r axroS2C., l00cA F.
in this curse, wV Ly , C1= 3 corresponds to the highest frcroy
is the aXle ranee M,1x _ ,a
The frequenaysmplitudo and frequency-pbaee characteristics of a
similar submodulator without phase camponsation is shown by the dotted
curves In Figure 7. These curves only show the general tendency of the
continued accumulation of phase displauemont with increase of frequency.
In feat, the revursal o? phase takos place considerably more rap'dly on
acooumt of resomence peaks. Curves 2 and 4 .boa that in the layout
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described above, the ph=-O angle ix,. ransos for frequencies of up to 12 ?-
1/ ke, after which it gm-dually doe-eases, if the aeries ros9.ctnnce
is reduced (cuzuus 3 an(1 5), i:uti iSuudhUuuui uva (:~;u .?.4nt(::: :. i:uu+d.u:.+.H:~: u~
phase angle in frequency bands above 20 dcc; the negative- phase displace.,
went at frequencies of 14 - 15 ho is aornotthet incruesed. l; tan a phase-
compensating ey3tc is introdt cod, the sifomcdu2atiar4s ream ltan cncy-
amplitude eharaoteriutic is very satisfactory, Frequency diotortion not
exceeding 2 decibels (curves 2. 3 and 4) can be obtained at the nigaeat
frequencies in the audio spectrum, trhereae at f &ira::cioo of 20 - 30
he a considerable restricting cffoo1 sey ?ccual.t.
1M0DUI ATCR 0 RATION IN TILE VARIABLE AISZACF ENT SYSTEM
Until recently, the Class A.aycitem rue generally accepted for the
operation of eubmodulator tubes. Tue power deficiencies of this system
are well known, and its use in the submoduletor noticeably reduces the
overall afficiancy of the r",otion. Another disadvantage of the Clean A
system is the impossibility of making good use of power tubes owing to
the c nmtription and dieeipation,, at their plates, of an amouuti of poci r
exceeding the meximan pernisai.ble quantity. Nevertheless, this is
particularly necessary for sv"Gnadulators in high-level modulation systems
where the modulator grid current impulses are very large. The above-
mentioned disadvantages also limit the reduction of direct current in the
modulator tubes inasmuch as, they :,oul.3 require an increase in excitation,
i.e., a further increase in the number of cubmodulator tubes.
For these reason, it was oseentisl to transfer the uubmodnlatorr to
a system which would perpit the wide use of Ito power tubes with a low
power consumption ac were modulation. Ono of the possible solutions for
th'.s_problea was the use of the-co-called "variablo displacement1' system
r ..1 the essence of rhioh is that the operating point in the dynamic
characteristic of a tube is changed is accordance with the signal iovdd5
ao that at a meacim?in value of the signal, the, operating point is located
olo41 th- linear section, and at zero modulation, in proximity to the
lover bend of the cum. '
with such a syatam, the average poser con6ilmptizow by the Li i:l.uVUWdwa
is substantially reduced. The position of the operating point corresponding
to the maximum modulation level can be reacted much higher up than when
using Class A, because in this came only that cart of the power which
supplies the submodulotor is dissipated at the plate. if there should
pie no protnaotad waximrom modulation and the naxim'r, signal level is
momentary,. an even wider use of power tubes is possible. It should be
noted that in this case the submodulator wotics continuously in Class As
i.e., its internal resistance, as a source of electromotive force, does
not tnnw!+an_
The adjusteent of the operating point on the ebarnateristie of the
tube is achieved by rears of introducing a euppicmentary displacement,
proportional to the amplitude of the si 1, into the submodulator'e
operating circuit. With this aim in view, a special detector sic should
be intro oed iat-1) the circuit, similar to that used in the modulation of
an F"? oselilater v11-4, variable carrier signals. Timo-conatani requirements
for an increase of volts a in the supplosentary displacement abd tor its pules
nation could, however, be considerably easier. Indeed, then the system is
regulated by, a push-pall Class A amplifier, voltage pulsations In the
std lemsatary displacement are fed is pbase into the grid circuit on both
aria, and thus can only produce diatirtion when there is a considerable
amount of esy stew in the amplifier. The tine taken +o in.nreaeo the
aupplemsntsry di.splaooucmt then there is a sharp increase In signal level
is only the time taken to change over the amplifier from the Class B
system (in which it rapid); gains, Its new level) to t!:e Mass systec.
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the signal voltage should be supplied to the detector by means of a special.
separating series amplifier (Figure 8). The grid voltage of this amplifier
can be supplied by means of a voltage divider from any preceding stage of
audio amplification (including the grid circuit of the subnodulator itself,
see Figure 8):
The load resistance F1 of the detector can be much greater than the
internal resistance of the tube, and therefore the voltage amplitude at a
position halfway along the secondary winding of the transformer T is in
practice equal tc the value of the supplementary displacement (Figure 8).
in this case, the tra.-naformer is loaded by a resistance equal to 2R. The
supplementary displacement voltage is supplied to the submodulator tube
.grid through a unique filter. The series elementrf this filter is the
grid leak~resistancs R of the auboodulator, and the.ehvnt element is the
blocking capacity C A series with the internal resistance Ri of the tubes
of the preceding etoge; the resistance Ri is in parallel with the plate
load R of this stage. Thus, the time constant for the increase of supple..
cantary displacement, even in the abarrce of q!7pa' ilk/ at the datecto: cut
put, cannot be made less than the amount,
CI V t A.R.}}
(I . :rA~1 C8"P
For submodulators in high-level modulation systems; the rrquired supple--
mantery change in displacement may reach a sizeable amount (300 - 500 v).,
in'cal ulating this amount, the orop in voitege at t.ra PlateiuaLtiub ras:s~?,'
awe of the modulator tubes should be taken into account. In this case,
Lion amplitude for the submodulator, etc,
static effects in the place circuit; U he ne ea-iLty for `icreaaing the excite--
and consequently an increase in distortion governed by the tube load; the
appearance of additional distortion at high frequencies, produced by non-
a Class B modulator. This latter systemhaa in addition many other defects au
for examples en. increase In the modulator tube's equivalent internal resistancb
to the filter of the submodulrtor'c plate fetid (if it has a separate filter)
and the necessity for the inclusion of a fixed grid-bias voltage tap.
However, theft requirements =at also be satisfied in the other system with
is completely reliable and aatisfaitcry for the tubes, and allows a sub-
stantial economy in power.
i)is*d7antagss in the system include the additional requirements in
conneetion with the olternatinrg-current power supply fry the rectifier
Lnnt2- a lengthy - rimnt on the operstion of a high-level modulator in
controlled /interrupted tonal ;.ignai, thoxod the complete able.: N.e
sort of additional noretutic effects x ve.rr.:d t')" time : >nxtant if t^.9
system does not give an increase in the nonlinear coefficient in comparison
with the normal Class A system. Oecillograma of the input and output vol-
tages of the modulation avwtar. (Figure 9? taken when aupp2 lag a .-atu;:.l:
Experimental verificatzun confirmed this principle. Measurement of
distortion with sinusoidal tone modulation showed that in practice., when
reducing the direct current six to eight time, the variabia displacement
operation of the eyrtem.
which may reach 100 or`more milliseconds. This howevdr does not impair the
IV. Sf4li'YFE Of lT SRM APPLTYMMIOa
A special feature of a preliminary-stage amplification system with feed-
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f
back, already described in our work g, is the necessity of having a supple-
mentary supply in the a+.ages for undistorted amplification. This requirement
is caused by the possibility of overloading these etagia within-phase com-
ponents of even harmonica contained in the feedback voltage at both high and
low frequencies. In the latter case, the appearance of even harmonic vol-
tage in the reverse-feed circuit is caused by the filter impedances in the
modulators plate supply.
In addition, the nonlinear character of the submodulator's load pro-
duced by the modulator tubes' grid 'current causes a characteristic dis-
tortion in the shape of the output signal. The feedback: compensates for this
distortion by supplying to the stages a preliminary amplification which
corresponds to the compensating impulse; the excitation curve for these
stages is ierived, for deep modulation, from this extended and peaked form
(Figure 10). A case occurred in practice, where the ratio of the peak ex-
citation value at 100 percent modulation to the corresponding value at 50
percent modulation was 3:1. there a preliminary amplification stage failed
to ensure undisturbed s-aprificatioa of the sharply peaked excitation cLrve,
the nonlinear distortion sharply' increases, and a further increase in modu-
lation level cannot usually he obtained.
The imposeiWW.'_ity of colculating this prnk excitation value beforehand
with sufficient accuracy made it necessary to design preliminary stages with
a supplemnvntery feed for amplification. When or^atruotiag the reaistence cir-
cuit of these steps, the good one of voltage amplifier tube', necese}tested an
Leoraaad of the plate supply oltago. If this is undoeirable, the layout
shown In Figure 11 will be extremely useful. The aeximum phasedieplaoesast
obtained in the abeorce of supplaw,,Asr~-,phase red,:anl, '3y using this circuit
in one of the stages i;: a high-level rrroculat!.on system, the limits or unais
BACY,.^ROUND OF A liCnl^AIED OSCILLATOR '
Ii car.-lunion, the reader's attention is dray to the influence of feed-
La-k in tea modulation system on the background c.eatco by the oscillator tubeO
supply aource6~
Owing to the fact that the feedback is usually produced from the primary
circuit of the modulation trenAforner, it nab considered until runen'ly theft it
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M, TRK TED
$
was not involved in the pe.n:Atiu moduirtioo aet up ,., by the inoculated osciliato
supply sources. (This remark does not apply to certain layouts in new trans-
mitters where there is n supplementary selective feedback for the suppression of
the most outstanding background components,) This theory is, however, not en-
tirely true, inasmuch as it is evident that the vodulation level of this para-
sitic modulation chiefly depends on the size of the e.,uival.ent resiatx.nce of the
modulator tubes in relation to the secondary circuit. The latter, as is knoen,
is in its turn determined by the feedback level.
Figure 12 shores an equivalent circuit which permits the evaluation of the
oscillator's parasitic modulation set up by voltage ripples in the plate supply.
Besides the main L-Lype filter LCf the layout includes a second filtering
unit, formed by the inductance of modulator choke coil L. and the oscillator's
equivalent resistance, The oscillator's resistance is in parallel with the
circuit formed by C',l (modulator's blocking capacity) and R" (equivalent
internal resistance of modulator tubes in relation to the secondary circuit)
in series. Usually, the capacitive reactance of Cbl is much lass than R"im at
ripple frequencies of Coo ; in the rbsence of feedback, or with a deep feedback
of ore order 5i4-7 or less, R"im is much greater then Rp. Thus, the presence
of deep feedback may increase the filtration or the secondur, t two or three
time (becaase L
However, calculations ahow that this is only true when there is a very
large rectifier pulsation. With the usual six pheee rectifier circuit and a
normal filter (tnk$ng nonstatic processes, demodulation etc, into account) the
pulsation at the output of the letter is not great, and the sL'pplenserstery
filtration produced by the modulator choke ccil is more than r.rfficient.
Figure 13 shae. r_ circuit which ._llustratea the influence of the
modulator's equivalent irternal reclatanee on an oscillator's background, created
by the *AC supply to the filaments nr by the parasitic modulation of the excitation
voltage, It id evident frum this circuit that for audio frequencies, the
oscillator plate circuit impedance which reduces parasitic modulation is formed
by two parallel branches. The first, eonsieiing of the modulator choke coil
and' the plate supply filter joined in series, has an exceedingly large reactive
resistance at baokgroi.nd frequencies. The second is formed by the series
connection of R"im send Cbl, and as was shown earlier, its impedance ies .eter
..i. ' the ~ siw of ='i, Thu^, a ,:oras io..,. tic mod'ulatlcn fregien_eea t ;sates
ad r,,
circuit resistance chiefly depends on thssize of ?9im. t'ren it is small, i.e.,
when there is deep feedback, the background caused by the grid circuit or tha
oscillator filAment is much stronger than when there is no feedback.
It is particularly important to bear these remarks in mind during the
practical analysis cf the causer of background in transmitters employing plate
modulation. An 'nvestigation of the background produced by the oscillator was-
carried rut by extinguishing oa- excluding the modulator tubed and including a
resistance, 6q+.31 to the equivalent into-nal recist.ance of t'esc tubers at zero
modulation, in pergllel with the modulation transformer. This was verified'
during regulating mark on the high-level transmitter.
We still examine briefly the effect of the modulator and feedback tubes'
internal resistances' on the nonlinear distortions in trrnsiritturs at low audio
frequencies. As a result of the modulator wrrking in the Cuss -B system,
sizeable even,harmorie voltages of low modulation frequencies ore termed in
the M ter of the pl.-stn 3appl7 (uss.ally common to moderator and oscillator).
These voltages, v.ii.ch in practice reach 10 - 15 percent of the rectified vol-
tage modulate the oscillator, and the tfnnesmitter'a nonlinear coefficient at
low frequencies would therefore attain at least the same quantity. However,
owing to the presents, mentioned above, of the supplementary filtering unit
( L,,, , P yy G a, and /'( :., ) the ?uant.:lty of even harmonic voltage actually
reaching t}le oscillator plstel' several Limes smaller. This. 's true even
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for very high-level transmitters whose modulation choke coils have a correspond-
ingly small inductance. Naturally the presence of a feedback in the modulation
sfutem considerably increases filtration of these harmonica.
1. Model', Z.I., Person, S.V., Lebedev-Karmanov, A.I. and Pisarevskiy, A.M.,
"Questions on the theory of Deep Feedback," MST, NO 11, 1939
2. Person, S.V., Lebedev-Karmanov, A.I., and Pisarevekty, A.M. "High Leval
Modulation System with Feedback," IEST, No 2, 1943
3. Person, S.V., "A Method of fieducing Dynatron Oscillstion," Author's
Document No 228/323005
4. Burg, A.I., "Distribution of Current Between the Plate and the Grid
Circuit in Triode Tubes," I1M$'1', mo 11, 1937
7? Model', 2Q.I., Piiarevskiy, A.M., and Lebedev-Karsmnov, A.I., "A Method
of Increasing the Efficiency of a High X*vel Modulation System," Author's
Appended figures follop7
- 11
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RE TR ED
submodulatar'a Frequunci-\nmp1itude and fftquency-phuso
characteristics
ftero to = 0.34 ; i a Oo45
RESTRKh D
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nt,
AV
0'.9
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RE4M4'ED
tecycse.
Figure 9 VWVv V iVV'I
AL-our
1 , (a) _,j^ (b) ,~ "'0 (c)
(a) C;.aea As d1reat current 70 eA, modulation frequency 200 cycl?s
(b) Variable dieplacewent system, direct current 12 mA, modulation
frequency 200 cycles
(c) Variables luieplacement system, direct current 6 mA, undulation
Figure 10
Fig.,..* 11
STAT'
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