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Патент USA US2110664

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March 8i, 1938..v
D_ E_ HARNETT
_
2,110,664
MODULATION CIRCUIT
_
Filed Aug. 12, 1935
‘3 Sheets-Sheet 1
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March 8, 1938.
_
D. E. HARNETT
2,110,664
MoDULATIoN CIRCUIT
Filed Aug. 12.l 1933
5 sheets-'sheet 2
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ATTORNEYS
A2,110,664
Patented Mar. 8, 193_8_
uurrsoI STATES "PATENT
,
ori-‘lcs
2.11am
f MonULs'rroN omom'r
Daniel s. nar-'neta Tucuman. N. y.. misant» to s
Hazeltine‘ Corporation. a corporation of Dela
WIN
Application August iz. 193s. sensi 1ra-escasa,
ze claim». ici. 25o-_sol
The present invention relatesto a selective
circuit, and more particularly to an adiustably
selective system designed to respond simultane
ously to two or more widely separated fre
ß queneies.
The system includes appropriately selective. in
` ductively reactive and capacitively reactive ele
ments. so arranged and connected in- the system
that adjustment oi’ a sinsle variable element
10 produces two points ci maximum impedance
widely separated and bearing a fixed law of vari
ation with respect to each other as the variable
element is adjusted over a substantial range. In
its fundamental aspect, the circuit vmay be oon
sidered as a tuned circuit having two oscillatory
periods widely separated and moving simultane»
the two circuits will have. relatively no ei'lect
upon the voltages developed in the other oi'ithe
two circuits. In other words, a high-frequency
diil'erence is selected so that the tuning induct- '_
ance of the signal-frequency circuit will act as.
acholre at the oscillation frequency.
Similarly, "
with a high diilerence, the auxiliary alignment
condenser and the oscillation-frequency induct
ancc will constitute a high impedance in this
path at the signal frequency.
10
Having thus briefly described the invention. `
attention is invited to the accompanying draw
ings in which:
,
'
"
-llîi‘ig. l is.an elementary circuit diagram of thev
fundamental circuit comprising the present in 16y
vention:
'
.
‘
~
»
Fig. 2 is a circuitdiasram kof a superhetero
ously as the adjustable element is varied.
It is the object of this invention to produce dyne radio receiver,v including -a frequency
a circuit which may be tuned to two different changing circuit,l constructed in accordance with
20'
this invention; .
'
'
frequencies, by means of a singlevvariable ele
Fis.
3
is
a
diagram
of
a
circuit
similar
to
that
ment.
It is a further object of this -invention to'pro-` of Fig. 2. but'includins an additional radio-fre
quency amplil‘ler before the irequency-deter
duce a system in which a single variable ele
.
,
_
mment may be utilized to tune said system to mining circuit; and,
’Fig á isa diagram ci’ a similar selective cir
25 simultaneously vary two resonance~ frequencies
for supplying voltage corresponding to each of cuit. in which a Esingle tube is utilized tc act asY
the oscillatory periods, to a plurality of vacuum both oscillator and modulator. ‘
»Referring now more 'particularly to Fig. .1 of
tubes, thus providing a selective input system
i’or each of said tubes, which Ísystem requires the drawings. an input circuit connected to a
'so
a single adjustable clement.
_ source of high frequency. includes a primary inr
v
It is another object of this invention to pro
vide a modulation of frequency-changing cir
cuit for the input of a superheterodyno. which
requires a single variable condenser to simultane
ously tune to lthe desired signal and oscillation
frequency.
,»
`
-
.
These. and further objects of this invention.
will become 'apparent _from the following speci
fication and claims taken in connection with the
v40
accompanying drawings.
v
In accomplishing: the object of this invention.
with particular yreference to a superheterodyne
radio receiver for the purpose of illustration.'the
signal frequency tuned input circuit oi.’ the first
45 `detector or modulator ci’ the superheterodyne
~ i receiver, is tuned by c. variable condenser in the
‘ usual manner to receive audio-modulated carrier
waves.
The oscillation-frequency-determining
v " circuit. or oscillation circuit. as it will be referred
n" to hereinafter. Vis so connected in shunt across
thc signal-frequency tuned circuit. or signal cir
cuit. as it will be referred to hereinafter, that the
.same variable condenser may be utilized to tune
- _ the oscillation circuit.
A high intermediate tre'--
55 qucncy is chosen so that the tuning of each oi
ductance Li which is inductively coupled to a
secondary inductance La, included in the tunable
oscillatory circuit il. The circuit i6 may include
an additional inductancc La' and variable ccn-.
denser Cz, by means of which the resonance
frequency ci’ the circuit il may be adiusted.
In shunt with the variable condenser Ca is con
nected the tunable circuit is. which `includes
condenser C_a, inductance La and condenser C4,
which, together with Ga, constitutes a second
tunable oscillatory circuit. The input oi' tubs
i! includes the tunable circuit it. and the input
of the tube i1 includes the inductance La of the
tunable circuit it.
'
In'operation, the characteristics of the various
elemental of tunable circuits it and il are .so
chosen that a wide 'frequency difference will exist
between the resonance periods of each .of these
circuits. the frequency oi.' the tunable circuit ' Il
being higher than that oi' the tunable circuit i4.` 50
At the high resonant-frequency of the circuit il,
the total inductance o! circuit I4 will act ,as a
high-frequency choke. and at the lower resonant
frequency o! the circuit il, the'capacities C: and
C. will actas a high impedance. Furthermore.
2
2,110,664
I the series capacity Caand C4 of circuit I8, act to
limit the tuning rangeof the condenserl Cz with
- respect to the tunable circuit I 8, by means of
which the variation of the condenser Cz serves
to simultaneously tune the two circuits I4 an'd
I8 in the same sense to low and relatively high
radio frequencies, respectively, and over substan
tially equal frequency ranges.
It is obvious that
voltages of both frequencies will egrist across the
.150'
feed-back and oscillation circuits and, therefore,
may provide additional coupling between> these
i
two circuits.
«
~
_
That portion of the oscillation voltage which
is impressed across the condenser C2 will be im
pressed upon the input of the modulator or first
condenser C2 and therefore voltages of both fre
_detector tube I5 and thus be combined in the
input of said tube with received radio-frequency 10
quencies may be supplied to the input of tube I 5.
However, the/inputv of tube I1 is connected across
the inductance La and therefore is substantially
signal voltages which are also built up across the
.condenser C2. The bias of the tube I5 is so ar
ranged that it will act asa modulator,- and an
. isolated from the circuit I4, and consequently,
. s the tube I1 Iresponds merely to the frequency of
" the tunable circuit I8. Furthermore, since circuit
I4 is parallel-resonant with respect to condenser
C2 and circuit I8 is parallel-resonant with respect
to inductance La, an impedance maxima will ap
pear across condenser C2 at`the resonant Yfre
quency of circuit I4 and across inductance La' at
.2.10
cuit of. the oscillator tube I 'I yand the oscillation
circuit. The condenser C4 is common both to the
the resonant frequency of circuit I8.
-
« .
A particular application of this circuit to ’a
. ._ superheterodyne radio receiver is illustrated in
2'5 Fig. 2, in which corresponding elements are desig
nated by the same reference characters.
In Fig. 2, the antenna circuit includes the
antenna Il, ground I2, and input primary induc
' tance L1.. The inductance L1 is inductively cou
30 pled to the inductance La of the signal circuit I4,
which circuit is tuned to resonance with the de
v sired signal frequency by the variable condenser
l C2.
The' signal frequency voltage developed
1 across the condenser ‘C2 is impressed between the
35 control grid and cathode of the modulator tube
I5, which may be of the pentode type as, for
instance, the type 58. A gridebiasing resistor R5
audio-modulated intermediate frequency will be
produced in the output circuit of the modulator 15
tube.
f
‘
The output circuit ‘of the modulator tube I5
includes the radio-frequency choke L5 and the
high-voltage source I6. The screen grid of the
modulator tube I5-may be supplied with the ap 20
propriate voltage by means of a tap in the bat
tery I6. The high-voltage source I6 is by-pessed
for highV frequencies by means of condener C7.
That portion of battery I6 which supplies the
screen grid potential may be similarly provided 25
with a. by-pass condenser Ca.
The intermediate-frequency voltage developed
across the choke L5 is coupled through condenser
Cn 'to the input of the intermediate-frequency re
sponsive radio receiver 20 by which it is further 30
amplified, detected and reproduced in the usual
manner by «the loudspeaker 2| _. The details of
the remainder of the receiver and reproducer are
common to those found in the art and, therefore,
need no further description.
'I'he oscillation-frequency voltages impressed
across the inductance L2 may be transferred ca
is included in the cathode lead of the tube I5 for pacitively, or inductively to the antenna primary
the purpose of providing the proper grid bias, . inductance L1. Therefore, to prevent radiation
of the oscillation-frequency voltages, a neutrali 40
40 and a radio-frequency by-pass condenser C5“ is
zation arrangement may be provided as shown.
provided in shunt with the biasing resistor.y
. The oscillatorv tube I1, which may be of the This system comprises the connection between
triode type, as for instance type 56, has the oscil- ‘ the lower end of the feed-back coil L4 through
lation circuit I8 connected between its grid and the neutralizing condenser C1 to the upper end of
X
Y,
s
, the antenna primary inductance L1. The neutral
cathode.
The oscillation circuit <I8 comprises in series . izing capacity C1 is ,so adjusted that the feed
the inductance La, the alignment condenser Ca, back of the oscillation-frequency voltage to the
the variable condenser C2, whichds common to upper end of the coil »L1 is just sufficient to 'neu- _
tralize that transferred thereto by the tuning in
„
50
The oscillation frequency is controlled by the ductance Ia.
Appropriate cathode heating circuits may be
variable condenser C2, the capacity range of
which is limited relative to its effect upon the provided and these, together with' the voltage
oscillation frequency by the alignment condenser `- source represented by the battery I6, may be the
‘Cs ~and to some extent by by-pass condenser C4. vsaine as those provided for supplying the various
55 A paddingycondenser Cp, for assistingthe align
voltages required in the receiver 20.
As above stated, the oscillation frequency
ment, is connected between the junction of in
the tuned input circuit I4, and condenser C4.
50
ductance Le with condenser C: and ground, and
is, therefore, substantially in shunt with _the in
ductance La. The resistor R4 is for th'e purpose
60 of providing the proper bias on the grid vof the
oscillator tube I'I. lThe bias is produced by the
grid current and limits the oscillation amplitude.
The plate electrode of the tube I1 is connected
chosen should be considerably higher than the
frequency of the signals which it is desired to re
ceive.
For instance, an intermediate or differ
ence frequency of 4800 kilocycles may be selected, 60
in` which event, in order to cover the broadcast
band of from 550 kilocycles to 1500 kilocycles,
the oscillation-frequency circuit I8 mustl tune
through the coupling resistor Rz’to a. source'of
through a band of from 5350 kilocycles to 6300
high potential indicated as the battery I6. A
radio-frequency by-pass condenser Cv is` provided
kilocycles. Therefore, the percentage variation
across the battery I6.
'
of> capacity required to tune the oscillation in
ductance L3 through this range of frequencies be- '
The radio-frequency voltage ñuctuations, which
ing rather small, the condenser C3 maybe of such
lare developed across R2, are impressed upon the
70 oscillation circuit bythe feed-back circuit which
low capacity- that it will present a very high im
pedance to voltages‘of the signal frequency. In
other words, there will be but slight loss of sig
' includes vthe connection through the condenser Cs
to thelow'er end'of the inductance L4 and the
blocking condenser C4. The inductances La and
L4 are inductively coupled, thus providing an elec
75 tromßgnetic' coupling between the feed-back cir
nal-frequency voltage _through thev condenserV C;
and inductance La, which are in shunt with the
inductance La. The impedance of the inductance `
Le, which is in shunt with the condenser C2 across
'is
3
2,110,064
which voltages ofthe oscillation frequency are
developed, is so lhigh relative to oscillation-fre
quency voltages that vit will have a _negligible effect>
on these voltages.v
,
ì
' Thus, ~an arrangement has been produced in
which the single condenser C2 may be utilized to
tune4 two inductances to considerably different
frequencies, and the voltages of the two frequen
V cies which are» developed across the single variable
10 condenser may be impressed -upon the input of
the modulator tube I5 and there combined to
produce the modulated intermediate frequency
in the usual manner.
‘
y
‘
. The condenserCs acts, as has been stated above,
15 to limit the range of the condenser C2 and thus
acts as an alignment condenser by means of
» which the diiïerence between the frequency of the
signal currents and the frequency of the oscilla
tion currents may be maintained substantially
20 uniform as the condenser Ca is varied to tune the
input circuit throughout theA tuning range. The
25
input’ of the radio-frequency amplifier tube 8.
The output of the amplifier tubeA 8 includes pri
mary inductance Li, which corresponds _to the
antenna inductance Li of Fig. 1.~ This primaryV
’inductance vis inductively’coupled to the second
ary inductance Lz of the signal-frequency circuitl
Il. With this arrangement, the necessity for the
neutralizing condenser Ci of Fig. 2 is` obviated, as . '
the oscillator-frequency voltagesimpressed across
the inductance’Lz will be effectively yblocked by
the unilateral transmission characteristics of the
screen grid tube 8. The tube 8' may for instance
be a pentode, as shown, although any other suit
able tube'may be used. It-is obvious, of course,
that the input of the tube 8 might be untuned, in 15
'which event the tube would constitute a coupling`
tube. The condenser of the tuned circuit 1 may
be connected as shown, to be operated in a uni
control manner with the condenser Cz of the
radio-frequency tuned- circuit I4.'> ~
-
20
The output of the modulator is impressed upon
the input4 of the intermediate frequency amplifier
padding condenser Cp permits aÍ three point ad vof the receiverv20 by means of the tunedl inter- ~ ‘
justment of alignment to be obtained. The pad
ding condenser, Cp, isadjusted to correct the mediate frequency transformer I9, the primary
alignment when tuned to the upper end of the L5’ _of which: isincludedin the plate circuit of
broadcast band. The’inductance La is adjusted
togive correct alignment in the middle of the
band, and the condenser C3 is adjusted to correct
the alignment at the low-frequency end of the
band. These three adjustments are mutually de
pendent, but when properly made the circuits will
maintain their alignment 4as the condenser C2 is
tuned over its range. Although condenser C4 is
a blocking condenser and has such large capacity
35 as to affect but slightly the tuning of the oscil
lation circuit, its capacity may be so chosen as
the tube
I5. ~.
’
.
»
Appropriate voltage sources may be provided"
for the operation of the amplifier tube 8,/i and
these sources may be combined with those pro
viding the voltages for the remainderI of» the 30
circuit shown.
f
l
_
,
'
_Attention is now invited to Fig. 4, which shows
a similar frequency-changing circuit in -which '
a -single tube performs the function of oscillator
and modulator, corresponding parts being des 35
ignated by the same reference characters.- In>
to assist in maintaining the alignment, as well _, the circuit shown, the tube I5' is ,of the virtual
as to assist in maintaining uniforml oscillation
cathode> electron coupled type. Any other- type `_
of oscillator-modulator may be used if desired,-
voltages.
40
\
»
Although the various elements of the circuitv ` As shown,lthe tuned input circuit Il is connected
to number four grid, and this grid, the plate,
îsl-.own may have a wide variety of characteris
tics, the following approximate values have been and a virtual cathode, positioned just inside the
found to be satisfactory in producing anv oscillator
andv modulator system which' will operate to re-`
ceive` signals in the broadcast band lextending
45
from 550 kilocycles to 1500 kilocycles using an in
termediate frequency of 4800 kilocycles:
50
circuit comprises the condenser Ce, inductance
L4, and condensers C4 and C5.
This circuit >is
coupled to the oscillation circuit I8 bymeans
of the inductive coupling between inductance L4 50
and inductance La and by the capacitive coupling
inductance L1=1 mh.
inductance La=.2 mh.
inductance L3=.015 mh.
Inductance L4=.015 mh.
-
Condenser Ca=20 mmf .-500 mmf.
Condenser C3=30 mmf. l
‘Condenser C4-_-.1 mf.Y
number three grid, act as an electron-coupled
modulator. Number two grid acts as the oscil
lator anode, and is connected through resistor 45
Rz to the voltage source "I6. The second` grid
'
Condenser Ce=.001 mf.
Condenser Cp=10 mmf.
. of the condenser C4 which is common to these
-circuits. ' The oscillationl voltage is impressed
i
upon
the flrstf- grid, to 'which it is directly con
nected. In operation,.the first grid voltage -con~trois the cathode Vemission, and the lsignal volt
, age impressed on vthe fourth grid controls the
Resistor R`a=50,000 ohms.
portion of this emission which reaches the plate.
Resistor R4=20,000 ohms.
Although any appropriatel tubes may be used in
voltage of the first grid. The operation is other-- 60
„wise similar to that of the >circuits -shown in
the circuit described above, >a type 58 has been
found appropriate for use as the modulator I5,
This voltage, however, is powerless to affect the
Figs. 2 and 3.
'
-~
Whereas the invention has beenfdescribed‘as - .
and a type 56 has been found-to be appropriate ' a frequency changer for a superheterodyne radio
65.
for use as-the oscillator tube I1.
receiver, it may be utilized as the frequency
Figure 3, to which attention is now invited, changer for any heterodyne reception system,
shows a similar frequency-changing circuit‘for and it is equally applicable to frequency changers
use in a superheterodyne receiver. In this figure, for use in connection with the production of
parts corresponding to Ythose shown in Fig. 2 are 4'radiant energy'for any- purpose, or to any system
designated by the same reference characters. In in which it is desired to tune two resonant'cir 70
70 this circuit, however, ' an additional radio-fre-A cuits over a range in frequency.. maintaining a
quency amplifier is provided between the antenna ‘ constantgfrequency interval between _- them and
and the modulator tube I5. This circuit com
prises’the usual radio-frequency ytuned circuit 1 „ using only one variablereactance element.
which is inductively coupled to the inductance
1. A frequency-chanoine circuit which includes 75
75 L1 kof the antenna circuit and connected in the
4
2,110,664
a modulator tube and an oscillator tube, each
of said tubes having input and output terminals,
a first t'uned circuit connected to the input ter
'minals of one of said tubes and tunable to a
desired frequency, said circuit comprising an
- inductance and a variable condenser, a second
tuned circuit connected across the input termi
ductance and a variable condenser, a second
tuned'circuit connected across the input termi
nals of the other of said tubes and tunable to a
different frequency, said second circuit includ
ing a second inductance,y a. ñxed condenser, and
said first-mentioned variable condenser and hav
ing reactive constants so proportioned with re
nals of the other of said tubes and tunable to
spect to those of said first circuit that each of -
a different frequency, said last-mentioned circuit
said circuits has a high impedance to currents
of the frequency to which the other is resonant, 10
and a combined electromagnetic and electro
static coupling between the output of said oscil
lator tube and the tuned circuit connected to the
410 including a second inductance, a iixed'condenser
-and. said first-mentioned variable condenser and
having reactive constants so proportioned with
respect to those of said first circuit that each
of said circuits has a high impedance to currents
input thereof, whereby the resonant frequency'
of the frequency to which the other is resonant, ' of each of said tuned circuits is controlled by
15
and a coupling between the output of said 0s
said variable condenser to tune said circuitsl
cillator tube and the tuned circuit connected
to the input thereof, whereby the resonant fre-‘
quency of each of the tuned circuits is controlled .
20 by a single variable condenser to tune said cir
cuits through a band in frequency.
i
2. A frequency-changing circuit which includes
a modulator tube and an oscillator tube, each
of said tubes having input and output terminals,
25 an input circuit, a first tuned circuit, coupled
to said input circuit, connected to the input ter
minals of one of said tubes, and tunable to a
desired frequency, said circuit comprising an in
, ductance and a variable condenser, a second
30 tuned circuit connected across the input termi
nais of the other of said tubes and tunable to
a different frequency.,l said circuit including a
second inductance, a fixed condenser and said
first-mentioned variable condenser and having
reactive constants so proportioned with respect
to those of said first circuit that each 0f said
through a band in frequencies.
5. A radio-frequency circuit comprising a first
tuned circuit, tunable over a desired range of
radio frequencies and comprising an inductance 20
and a variable condenser, and a second tuned cir
cuit, tunable over a different range of radio fre
quencies and including a second inductance, a
fixed condenser, and s-aid first-mentioned vari
able condenser and having reactive constants so 25
proportioned with respect to those of said iirst
circuit that each of said circuits has a high im
pedance to currents of the frequency to whichl
the other is resonant, said second inductance and
said fixed condenser being so proportioned that 30
a variation of the capacity of said variable con
denser will tune both of said circuits throughout
a range in frequency and maintain> a substan
tially constant frequency diiference vbetween the
frequencies of each of said circuits, whereby the 35
frequencies of both of said circuits may be simul
taneously controlled by a variation of the capac
-circuits has a high impedance to currents of the
frequency to which the other is resonant, a
coupling between the output of said oscillator
tube and the tuned circuit connected to the input
thereof for producing oscillations of a frequency
determined by said circuit, and means for neu
and a variable condenser, and a second tuned
tralizing the oscillation-frequency voltage devel
oped in said input circuit, whereby the resonant
circuit, tunable over` a different but substantially
equal range of radio frequencies and including
frequency of said circuits is controlled by a single
variable condenser to tune each of said circuits
through a band -in frequency.
3. A frequency-changing circuit which includes
a modulator tube and an .oscillator tube, each
50 of said tubes having input and output termi
nals, a first tuned circuit co-nnected to the input
terminals of one of said tubes and tunable to
a desired frequency, said circuit comprising an
inductance and a variable condenser, a second
55 tuned circuit connected across the input termi
nais of the other of said tubes and tunable to
a different frequency, said second circuit includ
ing a second inductance, a fixed condenser, and
said first-mentioned variable condenser and hav
60 ing reactive constants. so proportioned with re
spect to those of said iirst circuit that each of
said circuits has a high impedance tol currents
of the frequency to which the other is resonant,
ity of said variable condenser.
6. A radio-frequency circuit comprising a first
tuned circuit, tunable over a desired range of 40
radio frequencies and comprising an inductance
a second inductance. a iixed condenser, and said
>first-'mentioned variable condenser, said second
inductance and said fixed condenser being so pro
portioned thateach of the circuits will have a
high impedance to currents of the frequency to
which the other is resonant, whereby both of
said circuits may be simultaneously tuned by 50
variation of the capacity of said variable con
denser.
'
,7. A radio-frequency circuit comprising a ñrst
tuned circuit, tunable over a desired range of 65
radio frequencies and comprising an inductance
and a variable condenser, and a second tuned cir
cuit, tunable over a different range of radio fre
quencies and including a second inductance, a
fixed condenser, and said first-mentioned variable
condenser, said second` inductance and said fixed
condenser being so proportioned that each of the
circuits will have a high impedance to currents
and a dual coupling between the output of said - of the frequency to which the other is resonant,
65 oscillator tube and the tuned circuit connected
and will resonate to a frequency having a definite 65
70
to the input thereof, whereby the resonant fre
substantially ñxed rel-ation to the frequency to
quency of each of said tuned circuits is con
trolled by a single variable condenser to tune
said circuits through a band in frequency.
which the other circuit resonates as both of said
circuits are simultaneously tuned through a band
in frequency by a variation of the capacity of
said variable condenser.
70
4. A frequency-changing circuit which in
cludes a modulator tube and an oscillator tube,
each of said tubes.`having input and output termi
nals, a first tuned circuit connected to the input
terminals of one of said tubes and-tunable to a
75 desired frequency, said circuit comprising an in
8. A radio-frequency circuit comprising a'iirst
tuned circuit, tunable over a desired range of
radio frequencies and comprising an inductance
and a variable condenser, and a second tuned cir
cuit, tunable over a different range of radio fre
75
2,110,006
s
lator tube, whereby. voltages of said signal fre
- quencies and including a second inductance, a
quency and said oscillation frequency are im
condenser. said second inductance and said fixed pressed upon the inputterminals ofsaid modula
condenser being so proportioned that each of the tor tube by said variable condenser, which vcon
circuits will have a high impedance to'currents denser serves to simultaneously control the reso
of the frequency to which the other is resonant nance frequency of each of said circuits. s
13. 'A frequency-changing circuit comprising a
andI will resonate to a frequency having a sub
stantially constant frequency difference relative nrst tuned circuit, tunable to the frequency oi'` a
to the frequency to which the other circuit reso v desired current itis desired to modulate and com
nates as both _of said circuits are simultaneously prising an inductance and a variable condenser.
a second tuned circuit, tunable -to an oscillation
tuned through a band in frequency by a varia
tion of the rcapacity of- said variable condenser. . frequency and ,including‘a second inductance. a
9. A radio-frequency circuit lcomprising a first fixed condenser. and said first-mentioned variable
tuned circuit, tunable over a desired range of condenser, said second inductance and said fixed
radio-frequencies and comprising an inductance condenser being so proportioned that a variation 16
of the capacity of said variable condenser will
and a variable condenser. and a second tuned cir
fixed condenser and said first-mentioned variable
`
-10
is
' cuit, tunable over a different but substantially
tune both of said circuits through a range in fren
equal range of radio frequencies and including a
quency and maintain a substantially constant
second inductance, a fixed condenser and said
first-mentioned variable condenser. said ~fixed
difference between the frequencies of said cir
cuits, and a modulator tube having its input ter 20V
minalscoupled to both of said circuits. whereby
high impedance to currents of the frequency of.
voltages of the frequencyI of both of said cir
'so- ‘condenser being so chosen that it will act as a
the first tuned circuit. and the elementsv of said
cuits are impressed upon the input of said modu
. second circuit being so»chosen as to cause said
lator tube. ~
14. A_frequency-changing circuit which com 25
prises a first tuned circuit. tunable to a desired
radio frequency and comprising an inductance
and a variable condenser, a second tuned circuit,
tunable to an oscillation frequency and including
80
a second inductance. a fixed condenser. and said
circuit tol be resonant to a frequency to which
` at the
first-mentioned inductance has a high im
pedanQQ. whereby each of said circuits will
E resonate at a distinct frequency without >affect
ing the voltages in the other circuit.
10. A frequency-changing circuit which com-l
prises a first tuned circuit, tunable to the fre
_‘ „quency of a current which it is desired to‘modu
first-mentioned variable condenser, said second -
inductance and said fixed condenser being so
'- late~ and comprising an inductance and a variable
Y. condenser, a sccondftuned circuit tunable to the
proportioned that a variation of thc capacity oi' ‘
said variable condenser will tune both of said -
frequency of a modulating current, and includ
circuits throughout a range in frequency and
maintain a substantially constant frequency dif»
. ing a second inductance. a fixed condenser, and
said first-mentioned variable condenser, and a ference between the frequencies of the current
modulator tube including input terminals, said ' in each of said circuits. means for producing an
input terminals being connected across said vari
oscillation-frequency voltage in the second tuned
able condenser, said variablecondenser serving circuit, and a modulator tube having its input 40
to impress voltages representative of both of said
terminals connected across said variable con
currents upon the input of said modulator tube
and' simultaneously controlling the resonance fre
quency of said circuits.
p
11. A frequency-changing circuit comprising a
first tuned circuit, tunable to the frequency .of a
current it'is desired to modulate, and comprising
an inductance and a variable condenser, a second
tuned circuit tunable to the frequency of a modu- »
50 lating current,l and including a second inductn
ance, a fixed condcnser,_ and said first-mentioned
variable condenser, a modulator tube including
input terminals connected across said variable
s condenser, means for supplying current of one of
55 said frequencies to said first tuned circuit. and
means for supplying an oscillation-frequency
voltage vto said- second tuned circuit, whereby
voltages of both of said frequencies'ma‘y be irn-l
pressed upon the input of said modulator tube
60 by said variable condenser, said condenser serv
' ing 'simultaneously to control the resonance fre
-
denser, whereby voltages of two frequencies, as
controlled by variation of the capacity of said
variable condenser, are impressed upon the input 45
of said modulator tubel
15. A frequency-changing circuit which corn
prises a first tuned circuit tunable to a desired
signal frequency and comprising an inductance
and a variable condenser, a second tuned circuit,
tunable to an oscillation frequency and including 60
4a second inductance, a fixed condenser and said
first-mentioned variable condenser. said second
inductance and said fixed condenser being so
proportioned that a variation of the capacity of 55
said variable condenser will tune both of said cir
cuits throughout a range in frequency and main,
tain a substantially ~constant frequency difference
between the currents in each voi' said circuits, a
modulator tube having its input connected across 60
said variable condenser. an oscillator tube having
its input terminals connected across said second
inductancepand
a feed-back circuit connected be-.
12. A frequency-changing circuit comprising a t
tween the output terminals of said oscillator tube
first tunedcircuit, tunable to a desired signal fre
'and coupled to said second tuned circuit for prc 05
65 quency and comprising an inductance and a vari
ducing oscillation frequency currents in said sec-_
` v quency of both of said circuits.
able condenser, Va second tuned circuit, tunable
>to an oscillation frequency and including a sec
Aond inductance, a fixed condenser. and said first
mentioned variable condensc'r, a modulator' tum
70 having its input terminals connected, across said
variablefcondenser, an oscillator tube including
input and output terminals, .said input terminals
being connected across the inductance- of said
second_tuned circuit. and a feed-back circuit
75 connected >to the output terminals of said oscil
ond tuned circuitfwhereby there is produced in
the output of said modulator tube a signal-modu
lated intermediate frequency having a substan
tially constant frequency as said variable con 70
denser is tuned to receive- signals covering a band
in frequency.
_
16. A frequency-changing circuit which includes
a first vacuum tube having input and output
terminals, a first tuned circuit connected across 75
6
g
-. >andes-1.
L
.
the input terminals of said nrst vacuum tube and> one of said tuned circuits into the other o_f said
tunable to a radio frequency, said circuit in
circuits,_and the inductance of one of said tuned
cluding an inductance and a variable condenser,' circuits being so proportioned as to act as a
a. second tuned circuit connected in shunt with radio-frequency choke with respect to the fre
said variable condenser and including in series quency produced in the other of said tuned
a ñrst fixed condenser, a second inductance, and circuits.
19. A radio-frequency circuit comprising a first
a second ñxed condenser.' said fixed condensers
and said second inductance being so proportioned Vtuned circuit tunable to a desired radio fre
quency and comprising an inductance and a
that said second tuned circuit will resonate at a
10 constant frequency difference from the frequency . variable condenser, a second tuned circuit tunable
to a different radio frequency, and including a
of the first tuned circuit as said variable con
denser is varied to tune both o/f'said circuits second inductance, a fixed condenser, and said
`first-mentioned variablelconden'ser, two ther
through a range in frequency, a‘second tube in
15 from one end of said second inductance and thejunction of said » variable condenser and said
mionic vacuum ~tubes each having a pair of input
terminals, a connection- from one of said tuned
circuits to the input terminals of one of said
second fixed condenser to the input terminals of
vacuum tubes, and a connection from the second
cludingfinput and output terminals, connections
said second tube, and a feed-back circuit con
nected to the output terminals of said second
20 tubef'or providing a dual feed-back coupling to
said second tuned circuit, said feed-back circuit
including in series, a feed-back condenser, athird
inductance, inductively coupled to said second in~
' ductance, and said second fixed condenser, where
25 by voltages of the frequency of both of said tuned
circuits, as controlled by said variable condenser,
I 'are impressed upon the input of said first-men
tioned tube.
‘~ 17. A frequency-changing circuit which in
30 cludes a modulator tube having input and output
terminals, a signal-frequency circuit connected
across said input terminals 'and including an xin-`
ductance tunable by a variable condenser to the
frequency of the current to be modulated, an
r35 oscillation circuit connected in shunt with said
variable condenser and including in series a first
fixed condenser, a second inductance, and a sec
ond fixed condenser, said fixed condensers and
said second inductance being so proportioned that
40 said oscillation circuit will resonate at a con
stant frequency difference from the frequency of
the signal-frequency circuit as said variable con
denser is variedto tune said signal-frequency
circuit' throughout a range in frequency, an oscil--
lator tube including input and output terminals,
connections from one end of said second induc
tance and the junction of said variable condenser
and said second fixed -condenser to said input
>
‘ terminals, and a»feed-back circuit connected to
50 the output terminals of said oscillator tube for
providing a dual coupling to said oscillation cir
cuit, said circuit including in series a feed-back
condenser, a third inductance,v inductively cou
. pled to said second inductance, and said second-
ñxed condenser, whereby voltages of the fre
quency of a signal current and an. oscillation
current, the frequencies of both of which are de
termined by >said variable condenser, are im
pressed across said variable condenser and upon
60 the input of said modulator tube, and whereby
a signal-modulated difference frequency voltage
15 i
tuned circuit to the input terminals of the other
of said vacuum tubes, whereby the frequencies
of the currents impressed upon the input of each 20
of said vacuum tubes may be simultaneously
varied in the same sense through diilîerent` fre
quency bands by a variation of the capacity of
said variable condenser.
».
‘
20. A ¿frequency-changing circuit which in
cludes a first tuned circuit comprising an in-`
ductance anda variable condenser, a lsecond
tuned circuit including a second inductance, a
fixed condenser and said first-mentioned variable
condenser and having reactive constants so pro- ‘
portioned with respect to those of said first cir
_cuit that each of said circùits has a high im
pedance to currents of the frequency to- which
the otherj is resonant, two vacuum tubes each
comprising input and output terminals, a con- 1
nection between the first of said circuits and the
input terminals of one of said vacuum tubes,
a connection between the other of said circuits
and the input terminals of the other of said
vacuum tubes, and a coupling between the output
terminals of one of said vacuum tubes and the
input thereof, whereby said tube and its asso
ciated circuits operate as an oscillator and modu
late currents impressed upon the input terminals
of the other of said tubes.
A
'
21. A radio-frequency circuit comprising a first
circuit tunable over a desired range of radio fre
quencies, a second circuit tunable over a sub
stantially equal range of substantially different
radio frequencies and having reactive constants
so proportioned with respect to those of said first
circuit that each of said circuits has a high im
pedance to currents of the frequency to which
the other is resonant, and an adjustable re
actanceelement common to said tunable circuits 55
and effective to tune them in the same sense over
their respective ranges.
22. A radio-frequency circuit comprising a flrst
circuit tunable over a desired range of radio
frequencies, a second circuit tunable over a sub 60
stantially equal range displaced with respect to
said ñrst-named range in the frequency scale
and having reactive constants so proportioned
with respect to those of said first circuit that
- 18. In a frequency-changing circuit, tuned cir
65 (cuits tunable to the frequency of a signal-fre' each o said circuits has a high impedance to 65
curren l of the frequency to which the other is
quency to b_e modulated and an oscillation-fre
resonant, and an adjustable condenser common
quency, respectively, each of said circuits inclúd
to said tunable circuits and effective to tune them
ing the same variable condenser, and a fixed con
denser included in one of said `tuned circuits in the same sense over their respective ranges.
23. A radio-frequency coupling network includ
70 for aligning the tuning of both of said circuits,
is produced 'in the output circuit of said moduf>
lator tube.
whereby the frequency to which eachof said
circuits Yis _tuned by variation of said 'variable
, condenser has a substantially constant difference,
ing _a plurality" of reactance elements, said net
work comprising- component resonant portions
having points of impedance maxima substan»v
l said fixed condenser being so proportioned as to , tially displaced on -the frequency scale, means
75 restrict passage of currents of the frequency of for substantially eliminating reactionpf said
' 7
/
t'
2,110,664
component portions upon ‘each other. and means
for .tuningl said network over a desired range and
for adjusting said >points in thesame sense and ~
to equal extents comprising lan adjustable re
actance element common yto said portions.
24. A radio-frequency coupling network includ-4
ing a plurality of> reactance elements, said net
work “comprisingr component resonant portions
across which appear voltage maxima displaced on
s
means for simultaneously >tuning said circuitsover a -range of frequencies and adjusting said
points of maximum voltage in the same direction
on the frequency scale comprising an adjustablev
reactance element common’to‘ said circuits', and
output circuits coupled to said impedance -ele
ments. x
.
v'
f
,
L
4
-
À
’ 27. A radio-frequency circuit comprising a first
circuit tunable over a desired range of radio fre
quencies, a second circuit tunable over la range
the frequency scale, means for substantiallyl of substantially different radio frequencies "'and
eliminating reaction of said component portions 'having reactive constants so proportioned with
for tuning said net--
upon each other and means
respect to those of said ilrst’circuit ~that each
of said circuits has a high impedance to currents
of the frequency towhich the other is resonant, 15
an adjustable reactance- element common to said
ing an adjustable reactance element common to` tunable circuits ‘and effective to tune them over.
said portions.
_
their respective ranges, electron-discharge means
25. A radio-frequency network comprising a having two input circuits and an output circuit,
` first component resonant circuit. a second com
tunable circuits being individually connected
having a‘point of maxi-y said
20 ponent resonant .circuit
to said input circuits, and a coupling between
mum impedance displaced on the frequency scale said output circuitland one. of said input fcircuits,
with respect to that of said first circuit.l means . whereby said electron-discharge means' and- its
for substantially eliminatingl reaction of said com
associated circuits operate as an oscillator and
ponent circuits upon each other, and means for modulate currents impressed upon the other of
work over a range‘ of frequencies and maintain
ing a substantially constant frequency difference
15 between said points of voltage maxima compris
25 simultaneously tuning said circuits over a range
¿said input circuits.
.
'
of frequencies and adjusting'their points of maxi
` 28. A radio‘frequency circuit comprising a first 1
mum impedance in the same direction and to circuit tunable over a desired range of radio`
.equal extents on the frequency scale-comprising frequencies, a second circuit tunable over a range
an adjustable reactance element’common to said « _of substantially different radio frequencies and 30
circuits.
`
26. A radio-frequency coupling system compris
having reactive constantssol proportioned with
respect to those of said first circuit that each
' ing a first resonant circuit, a second resonant « of said circuits has a high impedance to currents,
4 circuit having reactive constants so proportioned ofthe frequency to which thelgother is resonant,
with respectto those of said first circuit that each
of said circuits has a high impedance to currents
of the frequency to which the other is resonant,
a circuit for supplying radio-frequency energy to
said circuits,"said circuits including impedance
40
elements individual thereto across which appear
voltage maxima displaced on the frequency scale,
and an adjustable reactance- element directly as,
connected in circuit with, and common to, both
of said tunable circuits and effective to tune them
inthe same sense over their respective ranges.
' DANI’EL E. HAnNE'r'r.
40
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