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Патент USA US2137266

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Nov. 22, 1938‘.
'K ~ ‘
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N.>P.ìcAsE y'
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MULTIBANDl RECEIVER- '
f _original Filed Mai; 25, 1955
el“
2,137,266
4 sheets-sheet 1
è
.57
BY'
AUORNEY. _
Nov; 22, 1938.1.
N. P. CASE
2,137,266 .
MULTIBAND ` RECEIVER
original Filed May 25; 1935
'
4'. Sheets-Sheet 2
INVENTOR.- `
Naso/'v
`
.. €455
BY.
ATTORNEY.
Nov. 22, 1938.
N. P. cAsE
> 2,137,266
MULTIBAND RECEIVER
original Filed MayV 25,' 1‘935
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ATTORNEY.
Nòvfzz, 193s.'
Y N. P, çAsE
MULTIBAND RECEIVER
originai Filed May 25,. 1935
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_ INVENTOR.
'
«Naso/v f? C455 '
ATTORNEY.
2,137,266
Patented Nov. 22, 1938
UNITED STATES -
PATENT OFFICE
2,137,266
*n
MUL'rmAND' RECEIVER
Nelson P. Case, Bayside, N. Y., assignor to Hazel
tine Corporation,l a corporation of Delaware
Application May 25, 1935, Serial No. 23,376
Renewed October 2.7, 1936
11 Claims.
frequency coverage extending from around 550
kilocycles to around 1550 kilocycles (0.55-1.55
megacycles). The relatively narrow high-fre
This invention relates to multi-band radio re-_
ceivers, and particularly to multi-band tuning
systems for radio receivers and to methods of
operating the same.
quency bands are preferably so located and of
such frequency coverage as to include only the 5
_
Popular interest in radio reception now in
high-frequency broadcasting channels, domestic
cludes not only those programs transmitted in
the general broadcast bands, but those programs,
transmitted in the various high-frequency bands.
,In response to this interest, radio receivers, tun
and foreign, inasmuch as the'overwhelming ma
jority of the general public is interested only in
the reception of lprograms from broadcast sta
tions. In receivers for‘such broadcast reception, 10
able
over
wide
frequency
ranges,
have
been
placed
10'
on the market. These receivers, commonly the tunable ranges of the receiver, in the high
frequency bands, are preferably bands of 500
termed all-wave receivers, are generally difficult '
kilocycles (0.5 megacycle) frequency coverage.
vto tune to any particular channel in the high
Although 'the -invention is not limited to a re
frequency bands due to the fact that small dis
ceiver tunable over bands of equal frequency 15
15 placements of the tuningA element tune over a
coverage in any two bands, the preferred tunable
»large number of channels. Slow motion equip
ranges of an all-broadcast receiver, in accord
ment of some character is, therefore, customarily
provided between the operating control and the
ance with this invention, are the following: '
0.55-~ 1.55 megacycles
tuning element or elements actuated> thereby.
20 Such slow motion equipment, however,` add's con
siderably to the expense of the receiver, especially
5.8 - 6.3
megacycles -
In addition, such slow motion equipment impedes
rapid shifts between widely- separated frequencies
25 and is generally unnecessary and objectionable
when tuning in the general broadcast band.
9.5 _10.0 megacycles
11.6 _12.1 megacycles
15.0 -15.5 megacycles
17.5 _18.0 megacycles
The invention further contemplates, in the in
corporation of the above features in a receiver
l when made so that there is no backlash therein.
It is an object of this invention to provide a
tunable over two or more such broadcast and
method of tuning a receiver by which tuning to
individual channels in the high-frequency por
high-frequency bands by the operation of the
same tuning member,¿proportioning the reactive
30 tions of the radio spectrum is as easy as tuning
elements utilized for tuning each of the two or
more such bands so that operation of the tuning
to individual channels _in the low-frequency por
tions.
'
,
`
It is a yfurther object of this invention to pro
member between its limiting positions tunes the
receiver, for each of such bands, substantially
~ ' vide'a radio receiver which is easy to tune in e'aoh . exactly between the limits of the selected bands.
35 of two or more frequency bands widely separated ' This provision of the inventionl results in great
in the frequency spectrum, either by other bands ease of tuning in all bands as all the channels
within the limits of each of the selected bands
of the receiver or by bands over which the re
ceiver is notV tunable, which has a high gain per
stage in each .frequency band, and which is
204
5
are, in each band, spread over the complete oper
ating range of the tuning member. Further, the
40 _ simple in construction and relatively inexpensive _ channels- in each band are-spread over the full
to build.
45
’
_
f
range of the indicating dial, and the individual
- Other objects of this invention will become ap
channels within the respective bands are sepa
parent from the specification taken in conjunc
tion with the accompanying drawings and the
rated on the dial by spacings having magnitudes
in a ratio, from band to band in the order of de
creasing frequency, which is substantially great
subjoined claims.
s
,
.
The invention contemplates either a radio re
ceiver which is tunable both over the generalv
broadcast band and over one or morerelatively
narrow bands in the high-frequency portion of
er than the inverse ratio of the mean frequencies
of the bands, it being understood that adjacent
signal channels in each of the bands are gen
erally separated-by a constant frequency differ
the radio spectrum, or is tunable over` two or , ence, such as 10 kilocycles.
more relatively narrow high-frequency bands, at
least some of which are widely spaced from each
other along the frequency spectrum. The gen
eral broadcast band, in the United States, is a
band of about' 1000 kilocycles (1.0 megacycle)
Thus, when the fre-` 50
quency coverage vof the several bands is the
same, as is the case for the high-frequency bands
of the lexample given above, the individual chan
nels within the respective bands are separated on
the dial by spacings of the same order of magni 56
2
2,137,266
tude for all of the bands and tuning of the re
age. However, in terms of relative values, in
ceiver is thus as easy in any one band as in an
other, even though widely separated `therefrom
in the frequency spectrum and in any event tun
`ing over the high-frequency bands is greatly
facilitated over that with arrangements of the
prior art. Furthermore, the dial of the receiver
may be permanently calibrated for each band so
as to enable quick tuning of the receiver to in
dividual channels ln the respective bands.
In accordance with the invention, a high gain
is procured by maintaining a high L/C ratio for
each tuned circuit, not only in the general broad
cast band'but also in each high-frequency broad
15
cast band.
»
`
Further, in accordance with the invention, the
same variable tuning element may be utilized
for tuning a receiver over both the general broad
cast band and one ormore high-frequency bands,
20 or, alternatively, `a tuning element having a.
smaller value and/or a smaller range of values
may be provided for the high-frequency bands.
In the latter case, the two tuning elements pref
erably are controlled by the same tuning mem
ber and have their displacement indicated on
the same scale member, although, less desirably,
the two tuning elements may be controlled by i'n
dividual tuning members.
-
In accordance with another provision of the
30 invention, certain of the tunable systems of the
receiver may, for reception in certain bands, be
simplified in certain cases, particularly in the
case of a superheterodyne receiver, by utilizing,
in one or more of the signal-selecting circuits,
fixed tuned circuits resonant substantially to
the mid-frequency of the band selected for ref
ception.
-
En the drawings, Fig. 1 is a chart of the radio
frequency spectrum to aidl in explaining the in
vention; Fig. 2 is a circuit diagram, partly sche
matic, illustrating one embodiment of the in
vention as incorporated in a multi-band super
heterodyne receiver; Fig. 3 is a similar circuit
diagram illustrating another embodiment of the
it; invention; Fig. 4 is a circuit diagram of a multi
hand receiver similar to, but somewhat less com
plex
that illustrated in Fig. 3; Fig. 5 is a
circuit diagram of a portion of the receiver of
8 illustrating another modification thereof;
Fig.
is
circ‘ait diagram of a portion of the
receiver of
ating still another modi
fication th"
a portion. or c
aneth
'I is a circuit die 'fram of
cy ver of Fig. 3 illustrating
"
t of the invention.
Ref
trum is
l, the radio-frequency spec
_
tted in megacycles. The cross
hatched porti-_on designated c represents the gen
eral broadcast
The other cross-hatched
portions, designated b, c, d, e and f, are non
ccntigucus hands ci 0.5 magacycle frequency
coverage in the high-frequency portion of the
radio-frequency spectrum, positioned therein so
as to include all, or substantially all, of the high
frequency broadcast channels of the world. in
this connection, the term “high-frequency por
the ratio ofthe frequency coverage of the band
to the minimum frequency of the band, band a is
quite a wide band (the ratio being 1.82), while 5
bands b, c, d, e and f are relatively narrow bands
(the ratios ranging from 0.086 to 0.029). As
herein employed, the term “relative band width”
refers to the relative measure of the band width
as deñned above, and the term “frequency cover 10
age” is herein employed to indicate the absolute
range of frequencies included within a band,
independently of its position in the radio-fre
quency spectrum. A “relatively narrow band” is
herein defined as a band in which the ratio of the -15
frequency coverage of the band to the minimum
frequency of the band is a minor fraction (i. e.,_
less than 0.5). In accordance with this inven
tion, and as will be seen from Fig. 1, the rela
tive widths of the several high-frequency bands 20
are less than that of the general broadcast band,
so that the frequency coverages or tuning ranges
of the several bands are substantially less than
directly proportional to the mean frequencies of
the bands, and the magnitudes of the displace 25
ments of the tuning means required to effect sep
aration of adjacent signal channels within the
respective bands are in a ratio, from band to
band in the order of decreasing band frequency,
which is substantially greater than the inverse 30
ratio of the mean frequencies of the correspond
ing bands. Such an arrangement is to be con
trasted with the `conventional arrangements of
the prior art in which the relative Widths of all
the bands are approximately equal, the fre
quency coverages are directly proportional to the
mean frequencies of the bands, andthe magni
tudes of the displacements of the tuning means
required to effect separation° of adjacent signal
channels within the respective bands are in a 40
ratio, from band to band in the order of decreas
ing frequency, which is inversely proportional to
the mean frequencies of the corresponding bands.
Although not limited thereto, it is desirablethat
the several high-frequency bands be relatively 45
narrow bands having a frequency coverage oi’ the
same order as, preferably between one-half and
twice, that ci the general broadcast band. and
leaving hand Widths equal to a .minor fraction,
preferably not greater than two-tenths. While 50
eac” of the receivers herein ’described is tunable
rfi
the rela " ely
road, general broadcast
~‘ ’=' y narrow high-frequency
hands the limits of which substantially corre
.f respectively to
above-described limits
of hands o, c, d, e and ¿? having equal frequency
coverages, it will ice understood that the inven
tion is equally applicable te any receivers de
ed to tune over any :temeer or” high frequency
-
f either equal or unequal frequency cov
e having relative band widths substantially
narrower than those
the arrangements of the
prior art. in case the bands are ci unequal fre
quency coverage, the displacements of the tun
ing elemernJ of the receiver required to effect sep
aration ci adjacent signal chananels Within the
including all radio frequencies above 5.0 maga- , several régir-frequency bands may be less than
cycles and as excluding all frequencies œlovv- 5.0 for the lower frequency band but still they will
megacycles, and the term “high frequency” is -be substantially greater than inversely propor
herein deñned es any radio frequency above 5.0 tional to' the mean frequencies of the bands, as in 76
megacycles. The preferred limits of bands a, b, the conventional arrangements of the prior art.
c, d, c and î are, respectively, those set forth With
of such limits and location as are
in the previous tabulation of preferred tunable ' given in the example specifically mentioned above,
ranges. As may be seen from Fig. l, these bands .ita is to be observed that the separation between
are bands of the same order of frequency cover
at least some of _the high-frequency bands and 75
tionof the
7,5
which the relative width of a band ls defined by
spectrum” is herein defined as
3
2,187,266
selected bands. These oscillation circuits are se
coverage of such bands, being of the order of at _ lectively connected to the control grid of the
oscillator portion of the tube 24 through a cou
least several times the frequency coverage.
pling condenser 38 and the contacts 36 of a
y Referring to Fig. 2, the antenna or first radio
`others thereof is large compared to the frequency
frequency >selecting circuit ofthe superhetero
dyne receiver therein illustrated includes an
tenna I0, a plurality of primary inductances II,
individually designated IIs, IIz and, II1, fixed
condenser I2 and ground I3. Primary induct
10 ances II are inductively coupled to. a plurality
of secondary inductances I4, individually des-`
switch 31.- A tuning condenser 42 is selectively
connected in parallel with the condenser 43a
between the high potential terminal of the sec
ondary inductance 35a and ground, and in par
allel with condensers 45h-45j, inclusive, between
the low potential terminals of the secondary in
ductances 35h-35j, inclusive, through the con
tacts 40 of a switch 4I.
The output of oscillator-modulator tube 24 is
preferably being that indicated, in which- pri-` coupled, by means of a transformer 41, 5I, tuned
yby the adjustablyrf'lxed- condensers 4_6 and 52 to
15 mary lnductance II1 is coupled principally to' the intermediate frequency, to the input of the
secondary inductances‘l4a and I4b, in which pri
mary inductance Ilz is coupled principally to intermediate-frequency amplifier- 53. The out
physical arrangements _of these inductances
secondary inductances I4c and I4d, and in which
put of amplifier 53 is connected to a detector
and ‘source of automatic volume control bias
voltage 54. 1The output of detector 54 lacon 20
>nected to an audio-frequency amplifier 55, which
primary inductance IIa is coupled principally to
secondary inductances I4e and I4f. Adjustably
fixed'condensers I8a, 2lb, 2Ic, 2Id, 2Ie and 2li> in turn feeds into a suitable sound reproducer> 56. '
are connected across secondary inductances I 4a,
Preferably, variable tuning condensers 2i), 3l)~
I4b, I4c, I4d, I4e and .I4f, respectively, to form and
42 are ganged for uni-control, as indicated
tuned radio-frequency wselective circuits. ~ The
high potential terminals of these tuned circuits by the dotted line 60, Also, switches I6, 25, 31 25
~
25
are'selectively connected through contacts I5 of a `‘and 4I are preferably ganged for uni-control, a i
switch I5 to the control grid of a vacuum tube I1, -
illustrated as of the pentode type and `connected
' to operate as a radio-frequency amplifier.
The ì
indicated by the dotted line 6I.
'
It is vnot believed necessary to describe the con
ventional connections by which the various op
erating voltages are applied to the elements of 30
the vacuum tubes, or by which the AVC bias
voltage is applied to the control grid of vacuum
condenser 20 is connected across secondary in
,
tube
-I1 and to the control grid of the modulator
ductance I4a, between ground I3 and the ter
minal of inductance I4a that is connected to portion of the tube 24. All these connections, 35
other terminals :of these circuits are connected
to ground I3 through condenser I2.. A variable
35
switch contact I5a."
'
.
'
The anode of vacuum tube I1 is connected
through coupling condenser 23 to the control
grid of the signal-translating portion of the vac
uum ytube 24, illustrated as a heptode utilized as
an oscillator-modulator. Arranged tol be selec
tively connected in the signal input circuit of
vacuum tube 24, as by the switch 25 having con- g
unimportant to? this invention, are clearly indi
cated in the diagram. It is believed sufficient to
note that the cathode of vacuum tube I1 is con
nected to ground through a biasing circuit 52,
that the cathode of vacuum tube 24 is connected
to ground through a biasing vcircuit 63, and that 40
the element 64 in the direct-current feed to the ,
anode of vacuum tube I1 is a >radio-frequency
tacts 21, are a plurality of tuned radio-frequency
choke coil.
' variable condenser v30 is connected across induct
ductance 26a is connected in circuit between the ,
circuits comprising inductances 26, individually -» In considering the operation of the above-de
scribed system, it is assumed that the switches
45 designated 26a, 2Gb, 26e, 26d, 26e and 215i-, and
adjustably fixed condensers 29a, 3Ib, 3Ic, 3Id, I6, 2'5, 31 and 4I are initially in the positions in ’
3Ie and 3| f, respectively. One‘terrninal of _each which they are illustrated in Fig. 2. Under
of the inductances 26a-26j, inclusive, is connect-_ these conditions, inductance I4a is connected in
ed to ground through a fixed condenser 28. A circuit in the input section ofthe tube I1, in
ance 26a. The anode of the oscillator portion>
of the oscillator-modulator tube 24 is connected
output section of ‘Äthe tube I1 and the modulator
condenser 32, a plurality of primary inductances
55 33, individually designated 333, 332 and 331, and
an adjusta‘bly fixed\condenser ~34. Primary in
ductances 33 are inductively coupled to a plu
the tube 24. With these connections, variable
section of the tube 24, and inductance 35a. is
to ground through serially connected blocking , connected` in circuit in the oscillator portion of
rality of secondary inductances 35, individually
designated 35a@ 35h, 35e, 35d, 35e and 35j, the
physical arrangement of these inductances pref
erably being that indicated, in which primary in
ductance 831‘is coupledV principally to secondary
inductances 35a and 35h, in which primary in
ductance 332 is‘coupled principally to secondary
inductances 35e and 35d, ~and in which primary
inductance 333 is coupled principally to second
ary inductances 35e and 35i.
The high potential terminals of the secondary
inductances 35m-35j, inclusive, are connected to
70 ground through adjustably fixed condensers 43a
and' 44h-44j, respectively, while the low poten
tial terminals of these inductances are connected
tuning condenser 20 tunes the circuit 20, I2, -
I4a; variable tuning condenser 30 tunes the cir
cuit 30, 28, 25a;- and variable tuning condenser
42 tunes the circuit 42, 35a,- 34. Condensersv I2
and 34 serve as capacitive coupling devices to
complement the electromagnetic couplings in 60.
their respective circuits, in a manner well under
stood in the art. Condenser 28, and also -con
denser 34,V serve as series padding condensers
and may be adjustably fixed condensers. Ad
justably fixed condensers Iila, 29a and 43a serve 65
as parallel padding condensers.` The padding
condensers, once adjusted by the manufacturer,
are not ordinarily altered.
The values of inductance I4a, variable tuning I
condenser 20, ñxed condenser I2 and adjustably
fixed condenser I8a. in the ñrst radio-frequency
selecting circuit, the values of inductance 26a,
variable tuning condenser 3.0, fixed condenser 28
and adjustably fixed condenser 29a in the second
to ground through the adjustably ñxed con
densers 34 and 45b-45f, respectively, to form a
Iradio-frequency selecting circuit, and the values
75 plurality of oscillation circuits for the several
4
2,137,266
I of inductance 35a, variable tuning condenser 42 accomplishing this, condensers 44h and 45h re
and adjustably ñxed condensers 34 and 43a in - duce the maximum 'effective capacitance of the
çthe tuned oscillator circuit, are so chosen as to oscillation circuit and also the effectiveness of
obtain satisfactory operation .of the superhetero
variable tuning condenser 42. As herein em
5 dyne' receiver in the general broadcast band fa, ployed, the term “effectiveness” of a tuning ele- '5
(Fig. 1), utilizing all, or substantially al1, of the ment is used to denote the ratio of the maximum
full range of variation of variable condensers 20, eifective value of circuit _reactance of the same
30 and 42. During such operation in the general type as that of the >tuning element to the mini
broadcast band, the radio-frequency selecting cir
mum eiïective value of such circuit reactance,
10 cuits are tuned to resonance with the signal fre
as the tuning-element is varied between its maxi- 1o
quency by variable condensers 20 and 30. The mum and minimum values.
l
incoming signal frequency is thus selectively am
Thus, as a result of the action of condensers
pliñed and applied to -the control grid of the 44h and 45h in reducing the maximum eifective
_
modulator portion of vacuum tube 24. The signal
value of the capacitance of the oscillation circuit
15 frequency is therein modulated by the frequency ' and in reducing the eiïectiveness of variable tun- 15
produced in the oscillator portion of vacuum tube ing condenser 42, the maximum effective capaci
24, the frequency of the oscillations being con
tance in the oscillation circuit is considerably
trolled by the tuning of the oscillation circuitby smaller than the maximum capacitance of vari,
variable condenser 42. As is well understood in able condenser 42 and the net eiïective capaci
20 the art, such modulation of a` signal frequency tance variation in the oscillation circuit incident 20
produces a constant intermediate or beat fre
to variation of condenser 42 between its maxi
quency, which frequency is amplified in the in
mum and minimum values is considerably 4less
termediate-frequency amplifier 53 land is detected than the diiference between the maximum and
or rectified in the detector 54 to produce audio
25 frequencies of modulation of the incoming sig
nal wave. 'I'hese audio frequencies are ampliiied
in the audio-frequency amplifier 55 and are then
translated into sound by reproducer 56. Auto
matic control of the amplification of the receivedA
30 signals is effected by the action of automatic
volume control bias potentials produced in the
detector and automatic volume control unit 54,
and applied to the control grids of vacuum tubes
i1 and 24 and of the vacuum tubes in the inter
35 mediate-frequency amplifier 53.
When switches it, 25, iì‘l`-` and @i are actuated s'o
that the Varms of these switches are in engage'
ment with contacts i512, 27h, 3th and fliib, respec
tively, inductance iêib is connected in circuit in
m the input section of _the tube l1, inductance 25h
` is connected in circuit between the output sec
tion of tube Iï and the modulator section of the
tube 223, and inductance 35h is connected in cir
cuit in the oscillator portion of the tube 2&3.' In
ductance Mb, together with adjustably iixed con
denser 2ib, functions as a ñxed tuned circuit.
Similarly, inductance äßb and adjustably iixed
condenser Sib `Eunction as a fixed tuned circuit.
inductance
N
is
element in the circuit iif‘ib,
d'2
minimum capacitances of tuning condenser 42.
`
In a similar mannenwhen switches $635.3? and 25
4I are actuated so that the arms of these switches
are in engagement with other contacts, the in
ductances connected to such other contacts are
connected in the circuits with which the respec
tive switches are associated. Thus, only those in- 30
dividual inductances of inductances i4, 26 and 35,
having the same lettered suiiix, are connected in
circuit at any one time. Furthermore, each indi
vidual inductance connected in the first and sec
ond radio-frequency selective circuits, except in- a5
ductances Ilia and ita, is shunted by a separate
adjustably fixed tuning condenser (2l for the
ñrst radio-frequency selective circuit and 3| for
the second radio-frequency selective circuit) to
form a ?lxed tuned circuit tuned substantially to 40
the mid-frequency of the band of corresponding
letter (Fig. l). Also, each individual inductance
connected in the oscillator circuit (except induct
ance 35a) is provided with a separate, adjustably .
fixed condenser filiv in series with, and a separate 45
iixed condenser`
in parallel with, the tuning
condenser @2, prc'perly to fix the tuning limits of
the corresponding oscillation circuit by appropri
ately reducing the en'ectiveness of the variabie
„en
between the limits of
with the adjustably
`
i j ‘
>the c
‘ -
pending ie
55 theThe
inductance
values ci inductance
fixed condenser íîib in trie <
selective circuit, e
‘ '
and adjustabiy
radio-frequency sc
e cir
and/cr adjusted as te obtain i
stages a ñxed tuned circuit tin
to the mid-frequency of high-freeman
(Fig. l).
The values of inductance Sii
i
@5 ably _nxed condenser »'lyïiîz- and fixed condense*
-
cc’en'se, Subject
.-.lues
to tf‘ailatien ever-a ce
tively ‘wide range de¿..-endii en design, ie
tion and
_
.
ef'tiie bancs, .n i
in the oscillatcr stage are so chosen and» f^r ad»
justecl, having consideration for the .
for
other
the varlcns so
elements wili
tai*Yee> of
oi" but
deñnite
little "‘ lues
t:J
and minimum values er” variahie tin
mentioned, however, and the relative order ci
magnitudes of certain elements indicated.
denser t2, that the frequency of the oscii l
70 generated in the oscillator portion of the tane 2d
varies between such limits as tc produce tiieprede=
termined intermediate frequency for received sig»
nals falling between the limits ci high-:frequency
band b, as variable tuning condenser «i2 is varied
75 between its maximum and minimum vaines. In
ance.
Certain practical ccnsiderations :n.„ff 'ce
'For satisfactory Vcperation cf a superheterodyne "c
receiver over the general broadcast band d, eacfc
of the variable tuning condensers 26, 3@ and ft2
may have a maximum value of the order ci’ 45C
inicro-micrcfarads and a minimum value of the
order of 15 micro-microfarads. Adjustabiy :fixed 'gg
r
5
2,137,268
tained by the use of different inductances 35 for
single-leaf padding condensers having a' range the dinerent bands and by utilizing across the re
spective inductances for the high-frequency
from 2.5 to 30 micro-microi’arads.- Fixed con
densers I2V and 28 generally are of the order of ’ bands the relatively large variable`- tuning con
denser 42 in series with a small adjustably fixed
2000 micro-microfarads. Adjustably ñxed con
denser 34 generally is a multiple-leaf padding condenser 44 and in shunt with successive ones of
the fixed condensers 45b-45f, inclusive, of greater
condenser having a range from 200 to 500 micro
- value progressively in the order named.
microfarads and set to a value around 450 micro- l
It is to be observed that in the superheterodyne
microfarads.
receiver of Fig. 2, not ‘.,only may the frame and
The satisfactory operation of the superhetero
10
rotor of »variable condenser 42 be maintained
dyne receiver of Fig. 2 in high-‘frequency bands at ground potential, but also one terminal of
b, c, d, e and f generally requires thatin each each adjustably fixed condenser 44b-44f, inclu
radio-frequency selective circuit and in the oscil
sive, may be maintained at ground potential.
lator circuit of the receiver the inductances hav
Adjustment of condensers `44h-Mí, inclusive,
"condensers Isa, 29a and 43a generally are small
15 ing correspondingly lettered-suffixes decrease in
value progressively in the band order mentioned.
Adjustably ñxed condensers 2lb-2li, inclusive,
SIb-3U, inclusive, and 44b-44f, inclusive. are
preferably small, single-leaf condensers having a
20 range from 2.5 to 30 micro-microfarads. Fixed
condensers 45h-451', inclusive, increase in value
progressively in the order mentioned and gener
ally are at least several times greater than the
value to which the corresponding series condenser
25 44 is set. Illustrative of one set of values of fixed
condensers 45 which has been used satisfactorily,
when the intermediate-frequency was approxi
mately 460 .kilocycles, are the following:
Micro-microfarads
. ‘5b _-__.__».. _________ -L_ __________________ ___ 100
‘5c -_
.... __
' ^ 45d _
35
-
____ __
A
5
10
’
15
may thus be made without the introduction of ì
error dueto the body capacity -of the person mak
ing such adjustments.
The arrangement of the .
circuits by which this is accomplished results
in no substantial _sacrifice of the available volt- 20
ages across the secondary inductances, for most
of the voltage across the secondary inductance
of the oscillation circuit for each high-frequency
band is impressed upon the control grid of the
oscillator portion of tube 24. This desirable re- '25
suit occurs notwithstanding th'e subtractive eifect
of variable condenser -42 and ñxed condenser 45
in the inductive leg of theoscillation circuit, since
in the high-frequency bands the reactances of
these condensers are small relative to those of 30
the condensers 44,
.
150
It is to be observed further that, in the super
175
heterodyne receiver of Fig. 2, the selection of in
45e _____________ ..;. ______________ __` ______ _ .200
dividual channels in the general broadcast band a»
‘Ef ___
is effected by the tuning action of the ganged 35
-_
____
210
In summary, tuning of the superheterodyne re- „ variable -tuning condensers 20, 30 and 42, while
the selection of individual channels inthe high
frequency bands b, 0,412, e and Vf is effected by the
tuning actionv of variable tuning condenser 42
alone. The -physical actuation of variable tuning
condensers 20 and 30 simultaneously with the
ceiver of Fig. 2 iseiîected by first actuating the
control member 6| for the ganged switches i6, 25,
'31 and 4| to the position corresponding to the
40 band desired and then actuating the control
member 60 for the ganged tuning condensers 20,
30 and 42 to tune the receiver to individual chan
nels in the selected band. It is to be observed'
that, as a result of the system described, the indi
45 vidual channels in the various `bands are sep
actuation of variable tuning condenser 42 has l
no eiîectV when tuning in the high-frequency
bands` as, at such times, the former are discon
_ nected and iixed tuned circuits are employed in 45 _
the radio-frequency' selective circuits of the re
ceiver. -'I'he use of such fixed tuned circuits,
arated by displacements of the tuning member 60
and of the scale co-operating therewith, having
magnitudes in a ratio, from band to band 'in the
tuned substantially to the mid-frequencies of the
respective high-frequency bands, contributes ma
order of decreasing frequency, which is substan
terially tothe simplicity of the receiver of Fig. 2 .
and isnot an objectionable expedient for use
50 tially greater than the -inverse ratio of the mean
frequencies of the.` bands. Specifically, lin -the
arrangement described, the individual signal
in low price receivers inasmuch as the frequency
coverage of the respective high-frequency'bands
is relatively small, so that the attenuation of
signal frequencies at the ‘upper andlower limits 55
channels in the several bands are separated by
` displacements of the tuning member which are
55 of the same order of magnitude for‘all of the
of such bands fis not excessive.
bands. thus equally facilitating timing 0I the
. ,
In receivers of better quality, it is preferred
receiver in all of its tunable ranges. This feature , to vary the tuning >of thel radio-frequency selec
, has been obtained in the receiver of Fig. 2 without
increasing `the number of variable condensers> tive circuits in each high-frequencyv band as
well as in the general broadcast band. Fig. 3 ‘60
illustrates a superheterodyne receiver in' which
is accomplished. Elements in Fig. 3 cor
Furthermore, the superheterodyne receiver of lthis
Fig. 2 has a high over-al1 gain-in 8,11 bands. This responding to similar elements in Fig. 2 are sim
v
- is'liecause of the fact that, in- the first and second ilarly designated.
The principal difference' between Figs. 2 and 65
65 radio-frequency selective circuits,Y the values of 3, relative to the radio-frequency selective cir- Y
thefinductance and capacitance for each fixedA _
tuned circuit therein are so chosen for the several cuits, is that in Fig. 3 the secondary inductances *_
bands‘as to provide high LIC ratlos. High L/C » 'I4 and 26 are variably tuned within each high
ratios of the same order of magnitude for all frequency‘band, as in the case of the secondary
bands are also obtained in their circuits, inductances 35 of the oscillation circuit of Fig. 2. 70
notwithstanding the use, in the high-frequency A further difference between Figs. 2 and 3 is thatv
bands, of the same relatively large variable> tun- f in Fig.~ 3 the condensers for eachhigh-‘frequency
60 over that customarily provided lin a receiver tun
able only over the general broadcast band.
band of vb‘oth the _radio-frequency selective cir
ing condenser“ that is‘used fortlming-the oscil
Alatorcircuitintliegeneralband.
75
highL/C ratiosintbecircuitare ob
Y
cuits and of the oscillator stage are connected
to- their respective inductances only when the ,ß
6
2,137,266
tuned circuits- formed thereby are connected in
circuit in the several stages. This provision in
sures that the response of the receiver is not
iniiuenced by absorption dips which might other
wise be present due to the action of unused,
spuriously energized, tuned circuits.
Referring more particularly to the iìrst radio
frequency selective circuit, adjustably fixed con
densers 18h-13j for "-inductances I4b--I4f,4 re
10 spectively, in the ilrst radio-frequency selective
circuit of Fig. 3, correspond to adjustably ñxed
condensers 44h-44j for inductances 35b-35f, re
spectively, in the oscillator circuit of Fig. 2
15
20
’
25
circuits. Further discussion of the oscillator cir
cuit of Fig. 3 is believed unnecessary. 'I'he re
mainder of-the circuit illustrated in Fig. 3 is
similar to, and functions similarly to, that of
similar designation illustrated in Fig. 2, so no 5
further description thereof is given.
It may be noted that two automatic volume
control connections are provided for the first
radio-frequency sele'ctive circuit; one, including
high resistance I8a; is connected to the low po 10
tential end of'inductance I4a and is effective
when the receiver is operating in the general
broadcast band a; the other, including high re
and serve selectively to limit the maximum ca
sistance |92, is connected to the ungrounded
pacitances in the several tuned circuits of the terminal of variable tuning condenser 20 and is
iirst radio-frequency selective circuit to values eiîective when the receiver is operating in any of
considerably smaller than the maximum capaci- ' the high-frequency bands b, c, d. e or f. Resist
tance of tuning condenser 2li and to reduce the ance lila may be of the order of 0.2 megohm. Re
eñectiveness of this condenser. The condensers sistance |92 is preferably of the >order of 2.0
18 are selectively connected, through the con
megohms in order vto minimize the loading eiïect 20
tacts 1I, 12 of a switch 18, between the high on the tuned circuit when operating in band a.
potential terminals of the inductances I4 and The second radio-frequency selective circuit is
ground, the arm of switch 1I! being connected to provided with two automatic volume lcontrol con
the control grid of vacuum tube I1.
nections, similar to those associated with the ñrst
Fixed condensers 11b-11j in the iirst radio
radio-frequency selective circuit, the first connec 26
frequency selective circuit of Fig. 3 also serve tion including resistance 38a and the second
selectively to reduce, in the high-frequency bands,
the effectiveness of variable tuning condenser 20,
-and correspond to ñxed condensers 45h-45j, for
80 variable tuning` condenser 42 in the oscillatorl
circuit of Fig. 2.
'I'he condensers 11 are selec
tively connected, through the contacts 15, 16
of a switch 14, between the low potential ter
minals of the inductances I4 and ground and
35 eil'ectively in parallel with the tuning condenser
28. It is -to be noted that no condensers 13 or
11 are provided for the secondary inductance I4a
corresponding to the general broadcast band.
Referring now `to the second radio-frequency
40 selective circuit, it will be seen that it dliïers
further from the corresponding selective circuit
of Fig-2 in that inductances 28 are inductively
energized by primary inductances 181, 182 and
18a.' In this selective circuit, adjustably iixed
condensers 8321-831“, selectively connected in cir
cuit with inductances 28h-2U, respectively, in
the high-frequency bands by means of a switch
88 having sets of contactsBI and 82, correspond
_ to adjustably ilxed condensers 13b-_Hf for in
connection including resistance 88a.
'
In general, the operation of the superhetero
dyne receiver of Fig. 3 is the same as that pre
viously described for the receiver of Fig. 2; that
is, the switches (10, 14, 80, 84, 80 and 84 in this
instance, and preferably ganged for unicontrol,
as indicated by the d_otted line 81) are set to
the position corresponding to the band desired,
and then g‘anged tuning condensers 20, 80 and 42 35
are actuated to tune the receiver to the indi
vidual channels in the selected~band.
Further,
the receiver of Fig. 3 has the feature of the
receiver of Fig. 2 by which the individual chan
nels in the various bands are, in general, sepa
rated by displacements of the tuning- control
member 68, and of the scale co-operating there
with, having magnitudes in a ratio. from band
to band in the order of decreasing frequency,
which is substantially greater than the inverse
ratio of the mean frequencies of the bands. The
Fig. 3 arrangement is similarly specific to the
feature of proportioning the auxiliary reactance
elements oi.' the radio-frequency selector system,
50 ductances I4b--I4f, respectively, ' in the ñrst
so that the individual signal channels in the sev
eral bands are separated by displacements of the
tively to limit the maximum capacitance in the tuning condenser~ that are oi' the same order of
magnitude for all of the bands. 'I'he principal
several tuned circuits of the second radio-fre
quency selective circuit to values considerably additional feature of the receiver of Fig. 3 is
55 smaller than the maximum capacitance‘of tun
that the radio-frequency selective circuits are
ing condenser 38 and to reduce the effectiveness ,_ variably tuned in each high-frequency band by
of this condenser. Fixed condensers 81b-81f, the same variable tuning condenser employed to
selectively connected in circuit with inductances tune the corresponding selective circuit in the
28h-_28j by means of a‘switch 84 having sets general broadcast band.- To this end, the mini
of contacts 88 and 88, also serve vselectively to re
mum and maximum values of variable “tuning
duce, in the high-frequency bands, the effective
condensers. 2o and an are such that, when the
ness of _variable tuning condenser 88, and corre
receiver is adjusted for reception in generalspond to ilxed condensers 11b-_11j for variable broadcast band a, a11_the individual channels
condenser 28 in the iirst radio-frequency selec
within such band are covered by substantially the
tive circuit. Further description of the second entire motion of these variable condensers be
radio-frequency selective circuit is believed un
tween their minimum and maximum values.
necessary since it is fundamentally similar to the Further, the values oi theinductances I4b-I4f,
ñrst radio-frequency selective circuit.
adjustably fixed condensers 13b-18! and ñxed
Referring now to the oscillator circuit, the condensers 11b-11j associated with the~tuning
70 condensers 44 and 48 are selectively connected in condenser 28, and the values of the inductances
radio-frequency selective circuit, and serveselec
circuit with their respective inductances 38 by 2Gb-2812 adjustably flxed condensers IIb-83!
means of the switches 88 and 84-, having sets of and fixed condensers 8112-81! associated with the
contacts 8|, 82 and 88, 88, respectively. and con
tuning condenser 30. are such that all the indi
nected similarly to the selector switches 10 and ividual channels within each of the _high-fre
14 or 88 and 84 of the radio-frequency selective 1 quency bands are also covered by substantially 1I
~
_
2,137,2‘166
the entire motion of the variable tuning con- -
densers between their minimum and maximum'
with the arrangement of Fig. 5, 1t is to be ob- served that adjustably fixed condensers 13 are se
lectively connected in series> with variable tuning
condenser 20 selectively to reducethe- maximum
receiver of Fig. 2 and the advantages of the ‘ effective capacitance of the selective circuits, as
receiver of Fig. 3 isk illustrated in the receiver in Fig. 3. Further, the eiîectiveness of variable
condenser 20 is selectively vreduced in each high
of Fig. 4. In this latter receiver> the radio-fre
frequency ïband by the fixed condensers 11 se
quency selective circuits and the oscillator tuned lectively
connected in parallel therewith, and by
>circuit are variably tuned in each high-frequency
values.
'
_
_
A compromise between the simplicity of the
10 band as well as in the general broadcast band,
and this by the'same variable tuning condenser
in each circuit that is utilized to tune the corre
the adjustably-- iixed condensers 13 as well, asin 10
Fig. 3. The full voltage'across each tuned induc
tance is thus impressed upon the control grid
sponding circuit in the general broadcast band. ' of »the tube I1, the subtractive effect of con
Further, in the receiver of Fig. 4 the condensers denser I2 being entirely negligible due to its ex
tremely small capacitive ~reactance at the high
15. for each high-frequency band are connected to frequencies.
‘
'
their respective inductances only when the tuned
The circuit diagram of Fig. 6 illustrates, for the
circuits formed thereby are connected in the re
lated circuits of the receiver. However, in this
case only one inductance is used in each circuit
20 for all high-frequency bands.
firstqradio-frequency selective circuit of the re
ceiver of Fig. 3, an embodiment of the invention
utilizing a relatively large variable‘tuning con 20
This, of course,
somewhat reduces the gain obtained in certain y denser4 20 for tuning the receiver over the gen
eral broadcast. band and utilizing a very small
bands (particularly in bands b and c) dueto variable
tuning condenser |01 for tuning the re
the lower -L/C ratio, but the resulting receiver
still possess a moderately high over-all gain, as ceiver over each of the high-'frequency bands. 25
, All the _elements of Fig. 6 corresponding to simi
25 well as possessing great ease in tuning to the lar elements of Fig. 3 are similarly designated.
individual channels in all bands. .
The principal difference between the iirst ra
The principal diiierence between Figs. 3 and 4
is that the separate secondary inductances I4, 26 . dio-frequency selective circuit of Fig'. 6 and the
and 35, each »with lettered suflixes b to f, inclusive, vcorresponding circuit of Fig. 3 is the'substitution 30
of the small variable condenser |01 for the com
30 are replaced by three secondary inductances- |42,
bination,- in the several high-frequency bands, of
262 and 35e, in the ñrst and second radio-fre
variable tuning condenser 20 and the condensers
quency selective circuits and the oscillator cir
cuit, respectively. Incident to this diiîerence is 13 and‘11. As a result, condensers 13b-13j and
the further difference that primary inductances 11b-11j, and also switch 14, are dispensed with.
Further differences are: the addition of adjus
35 Ilz, H3, 182, 18a, 332 and‘333 are dispensed with.
To improve the operation l,of the receiver in the tably fixed condensers |08b--|08f, connected
higher frequency bands, an open-ended primary similarly to condensers 13b-'Hf in Fig. 3, to pro
winding 98 for secondary inductance 26a is pref
erably provided.
'
.
I-
*
All of the elements in Fig. 4, corresponding to
-similar elements in Fig. 3, are similarly des
ignated. It is believed that a detailed descrip
" tion of Fig. 4 and its operation is unnecessary.
Videpredetermined iixed capacitance selectively
in parallel with the small Variable tuning con
denser |01 selectively to reduce the effectivenessy 40
of the small variable condenser |01 for the respec
tive` high-frequency bands; the connection of
the low potential terminals of secondary induc
4When the variable tuning condenser employed tances I4b-|4f, inclusive, to ground through
in tuning in the general broadcast band is also.v fixed condenser I2; and a rearrangement of the
employed in tuning in the high-frequency bands, connection for variable tuning condenser 20 so
it is connected in circuit only when switch '
the arrangements heretofore described have been that
10
isp-in
the position corresponding 'to general
such as to connect the variable condenser in the broadcast band _a. `If desired, adjustable con
inductive leg of the tuned circuit when operating ' denser Illa, used as a parallel padding condenser
in the high-frequency bands. As explained .in
50
connection with the variable tuning condenser forvariable tuning condenser 20 in the general
broadcast band, may be- connected, as illustrated,
so that it is in circuit only when variable tuning
riiice of the available voltage across the tuned condenser 20 is in circuit.
,
inductance results'from such arrangements. n .
Variable tuning' condenser |01 is preferably ar
it is desired,~ho,wever, to utilize in any circuit ranged to operate conjointly with variable tuning
55"
all the available -voltageacross each tuned in - condenser 20, in which case condenser v|01 is con
ductance, the circuit arrangement for such cir
veniently constructed by insulating an end stator
cuit or circuits may be as illustrated in Fig. 5,
plate of condenser 20 from the other stator plates
which is a modification of the iirst radio-ire- - of the condenser, and utilizing such separately
quency
selective
circuit
of
Fig.,3.
60
All the elements in Fi’g. 5 corresponding to sim- ' insulated end stator plate and the adjacent end
ilar elements of Fig. 3 are similarly designated. -rotor plate as variable condenser |01. As a re
The basic change in Fig. 5 over Fig. 3 is that sult, actuation of variable tuning condenser |01
‘42 ofthe receiver of Fig. 2, no substantial sac
.
for the high-frequency bands, adjustablyl ñx‘ed
65 condensers .13 and their respective fixed con
densers 11 are connected in series between the
- high potential terminals of the windings I4 and`
is effected (as illustrated) by operation of the `
-same tuning control member 60 that serves to 65
control the vtuning of the receiver to the indi
vidual channels in the general broadcast band.
ground, while the variable tuning condenser _20 -An electrostatic shield is preferably interposed
is connected in parallel with> the iixed condensers between the separately insulatedend stator plate
11 through the contacts 16 of switch 14. By this -and the other stator plates in order to minimize 70
expedient, the second arm of switch 14, and >con- » undesirable couplings between such stators when
.tacts `15 engaged- thereby, are dispensed with, operating in the high-frequency band. Alter
natively, but less desirably, variabletuning con- _
the low potential terminals vof secondary induc
tances
`nl
I4b--I4f,
inclusive, 'being . connected '_ denser I 01 may be a structurally separate con
through condenser I2 to ground. l
. ’
denser the control of which is effected by a con.- ,75
8
2,137,286
` trol member individual thereto, with provision
secondary inductances Il, and the permanent
that the displacements thereof are indicated on
the same scale as the displacements of tuning
control member 60. Still less desirably, the con
trol of a structurally separate variable tuning con-‘-denser |01 may be eiïected by a control member
_ungrounded side of variable tuning condenser 20,
thereby eliminating the necessity of contacts 12
separated by displacements of tuning control
to which the receiver is tuned, as a result of the
connection of contact 1|a of switch 10 with the
of switch 10. To insure that the response of the
receiver is not influenced by absorption dips
individual thereto having its own indicating which might otherwise be present, due to the
scale. It' is essential, however, in each case that action of any unused, spuriously energized, cir
variable tuning condenser 20 be excluded from cuits, switch ||0 having contacts | || is provided.
10 the tuned circuit for each high-frequency band In practice, switch I |0 may be on the same switch
10
and that the entire tuning in each such band deck with switch 10. In'such case. switch ||0
be obtained exclusively by variable tuning con-. and its contacts ||| correspond structurally to
denser |01.
_
the portion of switch-10 in Fig. 6 having contacts
The minimum and maximum values of tuning 12. To avoid confusion, however, switch ||0 is
15 condenser |01, together with the values of the illustrated and designated in Fig. 7 as a separate
15
inductances Ilb-llf ~and adjustably fixed con
switch. Switch ||0 is arranged to short-circuit
densers |08b--|08f, are so chosen that the indi
the secondary inductance I4 for the high-fre
vidual channels in each high-frequency band are quency band next below the high-frequency band
20 member 60, and of the scale operated therewith,
position of switch 10.l The1short-circuiting of
having magnitudes in a ratio to the magnitude only the secondary inductance corresponding to 20
of the displacement of the variable'tuning con
the adjacent lower high-frequency band is `suf
denser 20 required to effect separation of the in
ficient' for many commercial purposes, since it is
dividual channels in the general broadcast band -found that such objectionable absorption dips as
25 which is greater than the ratio of the mean fre
quency of the broadcast band to the mean fre
quencies of the respective high-frequency bands._
Preferably, the values of the elements enumer
= ated are such that all the individual channels
within each band are, for each band, spread over
may occur are due primarily to the unused tuned 25
circuit involving such adjacent' inductance.
When switch 10 is in the position illustrated,
corresponding‘to general broadcast band a, the
arm of switch 10 is in engagement with contact
1|a to‘connect the control grid of vacuum tube I1 30
the complete operating 'range- of tuning control -with
the high potential terminal of secondary
member 00. In effecting this relationship, ad
inductance Ha and to short-circuit fixed con
justably ñxed condensers |00b-|08f are set so denser |0_9. Under these conditions, variable tun
that they progressively reduce the effectiveness
ing condenser 20 serves to tune the illustrated
35 lof variable tuning'. condenser |01 as the band stage of the receiver over the general broadcast
4within which the receiver is arranged to tune
'band a.
is higher in the frequency spectrum.
_
When switches 10 and ||0 are inthe position «/
The principles of the modiñcation illustrated corresponding
to any'hlgh-frequeney band, the
in Fig. 6 may beutilized in any one or more- of
40 the tuned circuits of the receivers heretofore de
scribed.
.
„
‘
,
The diagram of Fig. '7 illustrates, for the ñrst
radio~frequency selective circuit of -a (receiver, _a
modification of the circuit diagram of Fig. 6. All
45 the elements of Fig. 7,l corresponding to similar
elements of Fig. 6, are similarly designated.
There are two principal differences between Fig. 6
and Fig. ‘1. The ñrst of these diiferences is the
sò
elimination of the small variable tuning condenser
|01 for tuning within each of the high-frequency
bands, and the assumption of the functions of
condenser |01 by the relatively large variable
tuning condenser 20. This is effected by insert
ing a small iixed condenser |09 in series with
55 variable tuning condenser 20 when switch 10 is
in the -position corresponding to any high-fre
quency band, together with an arrangement such
tuning of the illustrated selective-circuit of the '
receiver over such highffrequency band is effected
by variable tuning condenser 20 having fixed con
denser |09 in series therewith, the operation in
other respects being 'similar to the operation of
Fig. 6 except that in high-frequency bands c, d,
e and f the secondary inductances Hb, Mc, Md
and He, respectively, are snorted.
If it is desired to short-circuit the secondary
inductances for all high-frequency. bands- below
that in which‘the receiver is tunable, this may
readily be effected in a conventional manner by
means of an arcuate follower at the outer end of
the arm of switch |I0 arranged ìto îmaintain cir
cuit between such arm and the contacts ||| for
bands below that for which switch ||0 is posi
tioned, or in any other conventional manner.
It is to be observed that in the diagram of Fig.
7, secondary inductance lla, together with cou
that switch 10 short-circuits small fixed condenser ,
pling condenser l2, is always connected across
|09 when it is in a position corresponding to the variable
tuning condenser 20, irrespective of the
general
broadcast
band
a.
'I'his
first
diiîerence
60
band to which the receiver is tuned.' No substan
may be incorporated directly in the diagram of tial
difllculty >results from such an arrangement,
Fig. 6 by dispensing with variable condenser |01 however, due to the fact that when the receiver
and' connecting small ñxed condenser- |09 be
is operating in any high-frequency b d the re
tween the control grid of ~tube I1 and the un
actance of secondary inductance Ila s relatively
65 grounded terminal of variable tuning condenser so high in comparison to that of variabletuning
20. In Fig. '7 condenser |09 is so connected. The
extra variable tuning condenser |01 of the modifi
cation illustrated in Fig. 6 ,is thus eliminated and
tuning of the first radio-frequency selective cir
70 cuit in all bands is thereby effected entirely b'y
variable tuning condenser 20.
,
The second principal difference between li'ig.` 6 .
55
condenser 20 that its effect on the circuit is
negligible.
The circuit elements illustrated in Fig. 7 are so
proportioned, as in Fig. 6, to obtain the previously
described desirable operating characteristics in 70
'
the several bands.
A_The radio-frequency selective circuit of Fig. '1.
and Fig. 7 is the permanent connection of the lends itself to a simple, compact and inexpensive
ungrounded terminals of adjustable condensers. construction for secondary coils I4 and adjustable
|8a and |08b-|00f, inclusive, to their respective condensers- |8 and |00. Furthermore, such an ar-_ 75
9
.
»
'
2,187,266
rangement utilizes only one switch bank, only one
it to any one of a plurality of bands while main
addition, the gain obtained with the ‘selective cir
with the bandselected to effect separation of ad
jacent signal channels of the same- frequency
separation within the respective bands by dis
L/C ratios for the several bands that are v
_fixed condenser and no tuning condenser otherv taining
than the tuning condenser 20 necessary to tune of the same order of magnitude, and varying the
the receiver in the general broadcast band. In effectiveness> of said tuning means in accordance
^ cuit of Fig. 7 is considerably higher, particularlyA „
in the higher frequency bands, than that custom
arily obtained in multi-band receivers, and fairly
uniform for the _several bands.v
10' If it is desired to obtain gains -for the high
frequency bands greater than those obtained
with the 'selective circuit of Fig. ’7, and to have..
»such gains still more uniform for the _several
bands, the selective circuit of Fig. 7 may be .modi
15 fied by employing a separate condenser |09, pref
‘
placements of said tuning means that are of the
same order of magnitude for all of said bands.
2. In a multi-band> radio receiver, a tunable 10'
system 7comprising reactance means ofA a given
type, variable tuning reactance means >of the
opposite type connected in_circuit with at least a
portion of said first-named reactance means to
form a` circuit tunable overa given frequency 15v
band, auxiliaryreactance means of said opposite
erably of the adjustably fixed variety, for each of type, and switching means for including said.
the high-frequency bands, and selectively con
auxiliary reactance means in circuit with said
hecting such condensers |09 in series with vari
' tuning reactance means and at least a portion of
lable tuning condenser 20, preferably atl the low
ñrst named reactance means to form a cir 20
potential terminals of such condensers |09, by said
cuit tunable over a second frequency band and to
a suitable switch ganged with switch 10. In the
resulting circuit, condensers '|09 serveselectively modify the effectiveness of said tuning means in
to reduce the maximum eñ‘ectiv'e capacitance in tuning the circuit; said auxiliary reactance means
the tuned circuits for the several bands to values being >so proportioned, relative to the first two 25
reactance means and their circuit relation, that
25 considerably less than the maximum capacitance the L/C ratios of the circuits for the respective
» ` of variable tuning condenser 20 ‘(similarly as do
condensers 44 for the variable-tuning condenser bands are ofthe same order of magnitude.
3. In a multi-band radio receiver, a tunable
42 of Fig. 2), while condensers |08, assisted by system
comprising reactance means of a given
condensers |09, serve selectively to _reduce the type, variable
tuning reactance means of the 30
30 effectiveness of the variable tuning condenser 20 l ` opposite type connected in circuit with at least a
similarly, respectively, as do condensers 45 and 44
for the variable `tuning condenser 42 of Fig. 2. portion -ofÄ said first-named reactance means to
form a circuit tunable over a given frequency
In Fig. 2, however, the condensers 45 are in par
band,
reactance means of said opposite
allel with the variable condenser 42 alone, while type, auxiliary
and switching means for including said 35
in
Fig.
'7
(both
as
illustrated
and
as
modified
as
`
35
auxiliary reactance means in circuit with said
outlinedabove) the corresponding condensers tuning
reactance means and at least a portion of
I|08 are in parallel with the combination of the ‘ said first
two reactance means to form a circuit
variable tuning condenser and the small _series tunable Vover
a second frequency band and to
condenser. In the latter cases, therefore, the rel
modify the effectiveness of said tuning means in 40
atively
large
and
somewhat
expensive
fixed
con
40
tuningthe circuit, said auxiliary reactance means
densers 45 are not required.
Although the invention has been described in being lso proportioned, relative to the first two '
reactance means and their circuit relation, that
connection with the tunable systems of super
the
L/C ratios of the circuits for the respective
heterodyne receivers, the invention is applicable
to the tunable system of any type of receiver.
'Furthen although the invention has been de
scribed in connection with certain preferred bands
of frequencies, the invention is applicable where
other bands of _frequencies are involved. Thus,
the location and/or frequency coverage `oi? such
other bands of frequencies may differ from those
herein described, but so long as the receiveris to
tune to the general broadcast band and to at least
onehigh-frequency band, or is to tune ‘to’ at
least two high-frequencybands widely spaced in
the frequency spectrum either by other Ibands of
the receiver or by frequency ranges over which
the receiver~ is not tunable, this invention pro
vides that in such-cases the- receiver will be tun
able with ease, and with substantialdial spacings,
to individual channels in all such bands.
Inasmuch as many changes could be made in
.bands are of the same order of magnitude and 45
adjacent signal channels of the same frequency
separation within the respective bands are sepa
rated by displacements of said tuning means of ` -
the same order of magnitude.
4. In a multi-band radio receiver, a tunable 50
system comprising*V a plurality of reactance means
of a given type, variable tuning reactance means
of, the opposite type, a plurality of auxiliary Vre
actance means of `said opposite type, and switch
ing means for connecting, in one position thereof, 55
a -selected one of said first reactance means in
circuit with said tuning _means to form a cir
cuit tunable over a given frequency band and
for connecting, in the several other positions
thereof, selected ones of said first reactance 60
means in circuit with said tuning means and
selected on'es of saidauxiliary reactance means
the 'above constructions and many apparently, to form circuits severally tunable over 4different
high-frequency bands- each' .widely spaced up
widely different embodiments of this invention wardly
in the radio-frequency spectrum from said 65
could
be
made
without
departing
from
the
scope
Y
65
given
band,
each of saidauxiliary reactance>
thereof, it is intended that »all matter contained
means being so'proportioned relative to said other
in the above description or shown in the accom
reactance means and so connected in Ácircuit
panying drawings shall be interpreted as illus
`therewith by said switching means that the L/C
trative and not in a limiting sense.
ratiosv of the circuits for the respective bands 70
`
10 What is claimed is:
1. The method of operating a multi-band radio are of the same order of magnitude and adjacent
receiver having band-selecting'means and tuning signal channels of the same frequency separation
means adjustable between minimum and maxi-,f within the respective bands are separated b”y dis
placements ‘of said tuningA means of the same
mum settings, which comprises `adjusting `the re
75
-‘ order of magnitude.
active
constants
of
the
receiver
selectively
to
tune
75
1o
2,187,266
5. In a multi-band radio receiver, a tunable
system comprising; a plurality of inductance ele
ments of different values; two variable con
densers of substantially different maximum
values; a plurality of auxiliary condensers, one
for each of said inductance elements; and means
for connecting said auxiliary condensers effec
tively in shunt with their corresponding induct
ance elements and for selectively connecting the
10 larger variable condenser effectively in shunt with
the largest inductance element to form a circuit
tunable over a relatively wide low-frequency band,
or the smaller variable condenser effectively in
shunt with the other inductance elements indi
15 vidually to form circuits severally tunable ex
clusively by the smaller variable condenser over
denser having `a magnitude in a ratio to the mag
nitude of the displacement of said variable con
denser required to'produce separation of adja
cent signal channels of the same frequency sepa
ration within said given frequency band, which is
substantially greater than the ratio of the mean
frequency of the given frequency band to the
mean frequency of the high-frequency band.
8. In a multi-band radio receiver, a tunable
system comprising; two inductance elements of 10
substantially different inductance; a variable con
denser having a relatively large ratio of maxi
mum to minimum capacitance; two auxiliary
condensers each having a capacitance substan
tially smaller than the maximum capacitance of 15
said variable condenser; and means for connect
ing said variable condenser effectively in shunt
with the larger inductance element to form a cir
20 signal channels of the same frequency separation cuit tunable over a relatively wide low-frequency
band and for selectively connecting one of said 20
within the several bands are separated by dis
auxiliary condensers in series with said variable
placements of the variable condensers tuning condenser
and said series-connected condensers
the respective bands having magnitudes in a and said second auxiliary condenser eiîectively in
ratio, from band to band inthe order of decreas
25 ing frequency, which is substantially greater than . shunt with the smaller inductance element to
form a circuit tunable over a high-frequency
the inverse ratio of the mean frequencies of said band widely spaced upwardly in the frequency 25
bands.
different and relatively narrow high-frequency
bands, said inductance elements and condensers
being relatively so proportioned that adjacent
spectrum from said low-frequency band, said in
6. In a multi-band radio receiver, a tunable , ductance elements and condensers being rela
system comprising; a plurality of inductance ele
30 ments of different values; two variable con
densers of substantially different maximum
values and having common adjusting means; a
plurality of auxiliary condensers, one for each
of said inductance elements; and means for con
35 necting said auxiliary condensers, effectively in~
shunt with their corresponding inductance ele
tively so proportioned that adjacent signal chan
nels of .the same frequency separation within the 30
high-frequency band areseparated by a displace- .
ment of said variable condenser having a mag
nitude in a ratio to the magnitude of the dis
placement of said variable condenser required to
produce separation of adjacent signal channels 35
of the same frequency separation within said low
ments and for selectively connecting the larger' frequency _ band which is substantially greater
variable condenser effectively in shunt with the
largest inductance element to form a circuit tun
40 able over a given wide low-frequency band, or
the smaller variable condenser effectively in
shunt with the several other inductance elements
individually to form circuits severally tunableexclusively by the smaller variable condenser
45 over different high-frequency bands each widely»
spaced upwardly in the radio-frequency spectrum
from said given band, said inductance elements
and condensers being relatively so proportioned
that the displacements of the larger variable con
50 denser in tuning between adjacent signal chan
nels within the given band are of the same order
of magnitude as are the displacements of the
smaller variable condenser in tuning between
adjacent signal channels of the same frequency
55 separation in the several high-frequency bands.
'7. In a multi-band radio receiver, a tunable
system comprising; two inductance elements of
substantially different inductance; a variable
condenser; two auxiliary condensers; `and means
60
for connecting said variable condenser effectively
in shunt with the larger inductance element to i
form a circuit tunable over a given wide low
frequency band and for selectively connecting
one of said auxiliary condensers in series with
65 said'variable condenser and said series-connected
condensers and said second auxiliary condenser
effectively in shunt with the smaller inductance
element to form a circuit tunable over a high
frequency band widely spaced upwardly in the
70 radio-frequency spectrum from said given band,
said inductance elements and condensers being
relatively so proportioned that adjacent signal
channels. of the same frequency separation
within 'the high-frequency respective band are
75 separated by a displacement of said variable con
than-the ratio of the mean frequency of the low
frequency-band to the mean frequency of the`
high-frequency band.
-9. In a multi-band radio receiver having a'
vacuum-tube input circuit one‘side of which is '
effectively grounded, a tunable system compris
ing; two inductance elements of substantially
different inductance; a variable condenser hav
.ing one- terminal thereof effectively grounded;
two auxiliary condensers; and means for con
necting said variable condenser eñectively in
shunt with the larger inductance element with
the ungrounded terminal of said variable con
denser connected to the ungrounded side of said
vacuum tube input circuit to form a circuit tun
able over a relatively wide low-frequency band,
and for selectively connecting one of said auxil
iary condensers in series with said variable con
denser at the high potential side thereof and said
series-connected .condensers and said second
auxiliary condenser effectively in shunt with the
smaller inductance element with the high poten
tial terminals of both said auxiliary condensers 60
connected to the ungrounded side of said input
circuit to form a ,circuit tunable over a high
frequency band widely spaced upwardly in the
frequency spectrum from said low-frequency
band, said inductance elements and condensers 65
being relatively so proportioned that adjacent
signal channels of the same frequency separa
tion within the high-frequency band are sepa
rated by a displacement oi.' said variable con
denser having a magnitude in a ratio to the mag
70
nitude ofthe displacement of said variable con
denser required to produce separation of adja
cent signal channels'of the same frequency sepa
ration within said low-frequency band which is
substantially greater than the ratio of the mean 75
2,187,966
11
a portion of said ñrst-named reactance means to
frequency of the low-frequency band to the -mean form a circuit tunable over a given frequency
frequency of the high-frequency band.
band, auxiliary reactance means of said opposite
10. The method of operating a multi-band type and switching means for including `said
radio receiver having band-selecting means and auxiliary reactance means in circuit with said
a-tuning element variable between minimum and tuning reactance means and at least a portion
maximum values, which comprises adjusting the ' of said ñrst-named reactance means to form a
reactive constants of the receiver selectively to circuit tunable over a second frequency band and
tune it to any one of a pluralityof bands while- to modify the effectiveness of' said tuning means
maintaining L/C ratios for the several bands in tuning the circuit, said auxiliary reactance
that are of the same order of magnitude, and means being so proportioned, relative to the ñrst
varying the effectiveness of said tuning element ¿two reactance means and their circuit relation,
in accordance withy the band selected to efiect that the L/C ratios for the respective bands are
. separation of adjacent signal channels of the of the sameorder of magnitude and adjacent
same frequency separation within the respective v signal channels of vthe same frequency channel
bands by displacements of said tuning element
having magnitudes in a ratio, from band to band
in the order 'of decreasing frequency, which -is
. substantially greater than the inverse ratio of
the mean frequencies of the said bands. »
11. In a multi-band radio receiver, a tunable
system comprising reactance means of a given
' typev variable tuning reactance `means of thev
opposite type connected iny circuit with
at least l
Within the respective bands are separated by dis
Yplacements of said tuning means having magni
tudes in a «ratio from one of the bands to the
other in the order of decreasing band frequency,
which is substantially greater than the inverse
ratio of the mean Trequencies of the correspond
ing bands. ‘
NELSON P. CASE.
_
-
10
15
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