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Патент USA US2123001

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Patented July 5, 1938
uNireo stares
PATENT orties
Kenneth A. Chittick, Haddon?ield, N. J., assignor
to Radio Corporation of America, a corpora
tion of Delaware
Application June 30, 1936, serial No. 88,176
6 Claims.
'The present invention relates to multi-wave
band receivers and, more particularly, to tuning
or resonance yindicator systems therefor.
With this circuit, the indicator tube will not
begin to defiect until within approximately five
kilocycles of the center of the carrier. The maxi
present invention has for its object to provide
mum deflection is very sharp and occurs only on
an improved tuning or resonance indicator sys
tem wherein a uniform tuning response or res
onance indication over a relatively wide tuning
range including a plurality of wave bands, may
the exact center of the carrier Wave. The broad 01
ness of the “Magic eye” tuning is thus eliminated,
and the operator of the receiver is enabled to
be derived.
Heretofore, in providing tuning indications in
A further object of the present invention is to
provide a tuning indicator system in which the
sensitivity of the indicator device may be ad
justed for conditions which obtain in any given
locality in which the receiver is used, and for loss
of sensitivity because of aging ofthe tubes and
circuit elements. It will be appreciated that this
feature is desirable, since the receiver may be
operated in some cases in a metropolitan dis
trict and in the vicinity of a broadcasting sta
tion, and in other cases in remote portions of the
country, at extreme distances from broadcasting
stations,»and for compensating for aging of the
circuit elements and for differences in location,
a sensitivity adjustment of the tuning indicator
tube is desirable.
The invention will be better understood from
the following description, when considered in
connection with the accompanying drawing, and
its scope will be pointed out in the appended
response to received carrier waves or signals in
a multi-wave band receiver, a differing degree of
response has been obtained in one wave band
as compared with that in another, because of
15; inherent Acircuit connections tending to make
the tuning indications weaker on the higher fre
quency or’shorter wave bands. It is, therefore,
ani object of the present invention to provide
means havinga uniform tuning response as a
tuning indicator, whereby this operating charac
teristic may be overcome.
It lis a further object of the present invention,
to provide a tuning indication system of the
above character wherein a tuning indicator tube
25 of - theV electronic, grid-controlled type known
commercially as the “Magic eye”, which is pro
vided ïby the commercially available RCA 6E5
tube, may be used.
As is known, the deflection on the indicating
30 screen of a tuning indicator tube of the above
tune the same to exact resonance.
gram of a portion of a superheterodyne receiver
upon the control grid of the amplifier portion of
embodying the invention; and
Fig. 2'is a schematic circuit diagram showing
:It is also known -that the deflection or tuning
'indication as normally provided in commercial
radio receivers now on the market is relatively
broad;- This renders the tuning operation more
difficult on certain weaker signals as received
from more distant broadcasting stations.
Accordingly, it is a further object of the pres
ent invention to provide an improved tuning in
dicator system in which the response of the indi
cator tubev is substantially the same for all sig
nals received, vregardless: of the strength of the
.carrier wave and with a high degree of selectivity,
whereby the indication is produced only when the
receiver is tuned correctly to the desired carrier
wave or signal.
In carrying out the objects of the invention, a
50 tuning indicator tube circuit is provided in con
nection witha separate intermediate frequency
amplifier channel which controls the deflection
ofthe indicating portion of the tube, the inter
mediatefrequency amplifier further including a
55 f sharply tuned coupling transformer.
VIn the drawing, Fig. 1 is a schematic circuit dia
type, Èis proportional to the voltage impressed
the ~tube¿
(o1. 25o-_2m
a modification of a portion of the circuit of
Fig. 1.
Referring to the drawing, an intermediate fre
quency amplifier tube is indicated at 5, and is
coupled with an intermediate frequency coupling
transformer 6 to receive ampliñed signals from
preceding usual tuning and frequency changing 40
portions of the receiver. This portion of the re
ceiver is not shown, for the reason that such
receivers are well known and understood, and
the omission of the input end thereof serves to
simplify the drawing.
Intermediate frequency signals, amplified by
tube 5, are applied through an output coupling
transformer l, to a second detector tube 8, which
includes two diode rectiñers, in the present ex
ample, one of which is used for initial bias and
the other of which is used as a detector and for
automatic volume control purposes.
The detector diode is indicated by the anode 9
and the cathode l0, while the bias control diode
is indicated by the anode Il and the cathode l2,
the heater for the cathodes being indicated at
I3. This tube may be of the RCA 61-16 type.
The detector diode circuit includes the tuned
secondary I4 of the intermediate frequency trans
stage including the tube 39 and by a rectifier
stage including the device 4U.
The’amplifler tube V39 is of the high gain,
pentode type, having av cathode 4I connected with .
. former 1, which is connected between the diode
ground 42, a control grid 43 connected through
anode 9 and cathode I0, through an output re
a coupling coil 44 with, the lead I8, as indicated
sistor I5»-I6, with the'cathode end thereof con
at 45, to receive ka biasing potential therefrom,
nected to ground as indicated at I1.
a screen grid 46, a suppressor grid .41, and an
Automatic volume control potentials are ap
output anode 48. The latter is provided with an
plied to an automatic Volume control lead I8 from output circuitr49 in which is located the primary 10
the diode circuit, through a ñlter comprising a winding of an intermediate frequency coupling
series resistor I â and a by-pass capacitor 20. Ytransformer 5I, and, together with the screen
» The diode output resistor is also provided with a
grid, .is connected to a positive source of anode
shunt by-pass capacitor 2|.
¿ potential represented by the lead 52. Suitable
Audio frequency signals are derived Yfrom the> filter resistors and by-pass capacitors, 53 and 54,
diode output resistor by a tap connection 22, respectively, are provided in circuit therewith.
having an audio frequency output lead 23. In
The transformer 5I may be of the iron core
the absence of signals, a biasing potential is sup k type and is sharply tuned to the intermediate fre
plied to the lead I8, to establish thereon a nega-l quency carrier wave to prevent the passage of
tive potential with respect to ground suflicient ‘ Vsignals in a band wider than substantially ñve 20
for normal biasing of .therreceiving tubes. ' This kilocycles. The tuned secondary 55 is connected
potential is derived from a series bleeder resistor
25-26-21 connected between a negative supply'
lead 28. and ground 29.
between the anode electrode 56vof the rectifier
49 and a terminal of an output potentiometer 51,
the opposite end Aof which is connected to ground,
A tap point >3&3l on the b-leeder resistor is con
nected through a lead 3I and a filter comprising
as indicated at 58.
The cathode 59 of the rectiiier 40'is likewise
a series resistor 32 and by-pass capacitor 33, to
the cathode I2 of the bias supply diode. The
anode II of the bias supply diode is connected
30 through a lead 34 with the bias supply lead I8.
It will be seen that the potential existing be
tween the tap point 30 and ground 29, in connec
tion with the bleeder resistor, is applied to the
lead I8 through the ground connection I1, re
35. sistors I6, I5 and I9, and causes current to flow
connected to ground 60, thereby completing a
diode rectiiiercircuit through the primary Wind
through the diode II-I2 and the resistor 32, byv
them substantially ineffective in connection with
way of lead 3l, to the terminal at 30. It will also
be“ seen that the current flows through the diode
output resistor I5-I6, thereby providingr an ini
40 tial biasing potential »to the lead I8.
In the
presence of a received carrier wave, the diode
S-I 0' causes current to flow through the output
resistor I5-I6, and as soon a-sthe drop- in poten
tial increases above that established by the ini
45 tial biasing rectifier, the received carrier wave
serves to control the potential applied to the lead
I8, and thereby provides automatic biasing poten
tials for the receiving system.
The initial biasing potential may be reduced by
50 short-circuiting one of the resistor sections, such '
asA the section 21, by means- of a switch 36 which
is connected with the wave band exchange means
of the receiver, as indicated by the dotted connec
tion 31, whereby the automatic volume control
ing 55. 'I‘he latter, together with a tuning capac
itor 6 I, provides a sharply tuned input circuit for
the rectifier.
The rectiiier 4l) may be an RCA GHG tube, and
the remaining diode elements therein, as indicated at 62, are connected to ground and are not
used. The grounding connection serves to renderV
the rectiiier circuit. Y
The tuning indicator tube38 may be of the type
known as thev RCA 6E5, which comprises a. target
electrode 65 which receives Yan electronic bom
bardment from a cathode _66 and fluoresces with
a green light. The cathode is connected Vto
ground through a lead' 61 andA a shield` wire.v 68.
surrounding a signal input lead 69. 'I'he input`
lead 69> serves to- connect the control grid-10 of
the tube with the diode output resistor 51 through
a movable contact 1I thereon. The target 65 is
connected through a lead 12 with` a positive'anode
supply lead 52.
A i'ilter resistor 13. and by-pass> capacitork 14
are providedv in connection with the lead 69, ad
jacent to the contact 1I'. ' The filter resistor and.Y
capacitor provide a time delay means for pre
venting sudden changes in potential _from causing
55. potential applied to the lead I8 is rendered more
too rapid change on the grid 10. 'I'he grid 10 is
effective for certain wavel bands than for others. . associated with- the cathode 66, and is further
For example, it has been found that for the associated with an anode electrode 15 which is
shorter wave bands, the initial biasing potential connected with the anode supply lead 12, through
is preferably reduced to render the receiving sys
a series potential drop producing resistor 16.~
60 tern more sensitive and more readily responsive ’
A gridwire1-1: extends from the anode 15 ,to` a
to changes in carrier wave strength at low am
position between the cathode 66: and a portion of
the Screen or target 65, and casts an electronic.
As the automatic volume» control means is
shown and described only by way of example and
G5. is not per se, part of the present invention, the
same is believed to require no ‘further description.
In accordance with the invention, the tuning
indicator tube, indicated at 38, is arrangedl to re
ceive signal indications through a separate in
70 termediate frequency amplifier channel from Ythe
Y signals applied to the second detector,r 8, - and
from a point preceding the automatic volume Ycon
trol. For this. purpose, the indicator tube 38 is
preceded in the intermediate frequencyA amplifier
75.» channel by an intermediate frequency»A amplifier
shadow- thereon, prevent-ing; theY electrons from
reaching the target as the electrode 11' becomes
more negative with respect to the target.
YThis condition; is controlled by'the'grid 16,;
which varies the anode current through the anode
15 and resistor 16,V an increasing negative poten
tial on the Ycontrol grid 16, causing the anode
current to be reduced and likewise the drop4 in
potential through the' resistor 16. The electrode
11 is thereby permitted to approach the potential’
of the target and to cause the shadow thereon
to be decreased in area, .indicating a. change in
grid potential'on- the control grid 10.
This is made a function of the strength of the
received carrier wave by rectifying the carrier
wave and applying the resulting direct current
potential to the control grid 10 through the filter
In accordance with> the invention, as shown in
the present example, the carrier wave at inter
mediate frequency is applied to the pick-up coil
44 by coupling with the signal channel in the
intermediate frequency ampliiier preceding the
ic: automatic volume
control means or second de
tector, and for this purpose the coil 44 is coupled
with and forms part of the intermediate fre
quency coupling transformer 1, thereby receiving
1.5; energy from the secondary circuit comprising the
resonance frequency of the sharply tuned cou
a tap 8| for the lead 69 and is connected between
pling transformer 5| is then applied to the recti
fier 56--59. The direct current component of the
rectified carrier wave is applied to the rectifier
the tap 1l and ground whereby the voltage avail
resistor 51, the negative potential applied to the
grid 10, with respect to the cathode 66, is deter
mined by the position of the movable tap 1I.
In any given locality, depending upon the aver
age strength of received signals, or dependent
upon the sensitivity of the receiver resulting from
aging of the tubes, the contact 1l may be ad
justed to provide a sufficient negative potential
on the grid 1D in the presence of a received car
rier wave to just “close the eye” or provide a
desired minimum shadow on the fluorescent tar
40 get, for accurate tuning.
The device 1l, therefore, provides means for
adjusting the sensitivity of the electronic, grid
controlled indicator tube, while the sharply tuned
intermediate frequency amplifier not only pro
45 vides a strong, amplified signal for indicator pur
poses but provides this signal in a separate, sharp
ly tuned channel which admits signals in a band
of a predetermined width more narrow than that
of the main signal channel for the second detec
50 tor, resulting in a tuning indication at exact
able across the resistor 51 between the tap 'll
and ground is applied to the resistor 80. A por
tion of this voltage is then available at the tap 25.'
8l serving to reduce the voltage on the indicator
This reduced voltage is desirable for the normal
broadcast or “A” band since the signal strength
in that band is high. For the weaker signals in
the “B” and “C”, bands, for example, the voltage
may be increased to compensate by opening a
switch 82 in ground connection for the shunt volt
age divider 80, whereby the full voltage of the
tap 1! is available for the control lead 63. The
control of the switch B2 may be effected in any
suitable manner as by the connection indicated
whereby it is actuated in response to a wave band
1. In a radio receiving system having a main
signal channel, and a second detector and auto
matic volume control means connected therewith,
the combination with an electronic tuning indica
tor device having a control grid, of a carrier wave 45
rectifier device having an output resistor, means
providing a variable tap connection for the con
trol grid of the indicator device on said output
I claim as my invention:
resistor whereby a predetermined control poten
tial may be applied to the indicator device, a 50
Furthermore, by selecting the intermediate fre
quency energy or voltage from a point on the
automatic volume control means and detector,
signal channel preceding the automatic volume
said amplifier being more sharply responsive to
signals than the main signal channel, and means 55
for applying automatic volume control potentials
to said amplifier.
2. In a multi-wave band radio receiving system
having a main signal channel, and a second de
However, since the control grid 43 of the indi
cator amplifier is connected with the automatic
tector and automatic volume control means con
nected therewith, the combination with an elec
volume control circuit I8, exceptionally strong
tronic tuning indicator device having a control
55 control diode or rectifier device, which is also the
second detector in the present example, the tun
ing indication remains substantially “flat” re
gardless of the strength of the received carrier
The voltage divider resistor 8i] is provided with
tuned amplifier connected between said rectifier
device and the main signal channel preceding the
with the wave band switch connection 31 as shown
in Fig. 2 wherein the same parts and circuits have
the same reference numerals as in Fig. l.
Referring to Fig. 2, the grid lead 69 for the in
dicator tube is connected indirectly with the tap
1l through the time delay filter 13-14 and an
additional voltage divider resistor 80.
for the grid 10 of the indicator tube. lSince the
cathode of the indicator tube is connected to
ground, and therefore to the positive end of the
on bands X and A and closed on bands B, C, and
D, to provide a greater sensitivity for the latter
bands, thereby compensating for the lower car
rier wave strength available in the reception of
the .higher frequency signals. With this ar
rangement, the tuning indicator tube is substan
tially uniformly responsive, providing a sharp
tuning indication for all wave bands.
In certain receivers the sensitivity of the indi 10%
cator tube may be adjusted by providing a tap
connection similar to the tap 1l in-connection
Winding I4. The coupling is indicated in the
drawing by the line 30 connecting the two coils.
The carrier wave at intermediate frequency is
amplified in the amplifier stage 3S and the ampli
fied intermediate frequency carrier wave at the
2,5: output resistor 51 to provide a biasing potential
signals, respectively, the switch 36 may be opened
signals serve to control the gain of the ampli
grid, of a carrier wave rectifier device having an
fier in the same manner as the signal amplifier.
output resistor, means providing a variable tap
connection for the control grid of the indicator 65
device on said output resistor whereby a predeter
mined control potential may be applied to the in
dicator device, a tuned amplifier connected be
tween said rectifier device and the main signal
channel, said amplifier being more sharply re 70
An advantage in this connection lies in the fact
that the change in response effected by wave
band change for the automatic volume control
means is at the same time provided in the sepa
rate channel amplifier for the indicator tube,
70 since the control grid 43 is under control of the
automatic volume control means and operation of
the sensitivity control switch 36.
In a receiver having X, A, B, C, and D bands,
for receiving weather reports, standard broad
75 casts, police, short-Wave, and ultra short-wave
sponsive to signals than the main signal channel,
and means responsive to change in the frequency
response range of the receiving system for effec
tively changing the control grid connection with
said output resistor.
3. In a multi-wave band radio receiver, the
combination with an intermediate frequency am
plifier, of automatic volume controlv means re
sponsive to received signals conveyed through said
intermediate frequency amplifier, a tuning in
dicator device of the electronic grid-controlled
type connected with said intermediate frequency
ampliñer to receive signals therefrom at a point
preceding said automatic volume control means,
said connection including a high gain intermedi
ate frequency amplifier, a rectifier device, and a
sharply tuned iron core coupling transformer be
tweensaid amplifier and said rectifier device,
means for deriving a biasing potential from said
rectifier device for said tuning indicator device,
and means for adjusting the value of vsaid poten
to the signal channel of said receiver .preceding
said automatic volume control- means and being
controlledthereby, a signal rectifier device, sharp
ly tuned coupling means >connected between said
rectifier device and said ampliñer stage to apply
signals to saidY rectifier device in a frequency band
relatively narrow. with respect to the frequency
response v'band of the signal channel of the re
ceiver, a tuning indicator tube having a control
grid coupled to said rectifier device to receive
a portion: of the direct current potential there
from resulting from signal rectification, , and
means for varying said last named coupling to
control the sensitivity of said tuning indicator
device in response to wave band change.
6'. VIn a multi-wave band receiver, the combina- '
tial in response to Wave band change.
4. In a multi-wave band radio receiving sys
tion. with automatic volume control means ad-v
justable in sensitivity with wave band change, of
tem having automatic volume control means,
an intermediate frequency amplifier stage coupled
ï' the combination with a tuned signal channel con
nected with said automatic volume control means
to apply signals thereto, of resonance indicator
means comprising a sharply tuned-signal ampli
ñer connected with said signal channel preceding
i said automatic volume control connection, a diode
rectifier connected with said sharply tuned signal
amplifier to rectify signals therefrom, a diode out
put resistor in circuit therewith, a resonance indi
cator tube having a control grid variably Vcon
nected with said resistor to receive an adjustable
biasing potential therefrom in response to re
ceived signals, and means for adjusting said po
tential to compensate for changes in sensitivity
resulting from changes in wave band range of said
receiving system.
5. In a multi-wave band receiver, the combina
tion with automatic volume control means ad
justable in sensitivity with wave band change, of
Y an intermediate frequency amplifier stage coupled
to thel signal channel of said receiver precedingV
said automatic volume control means and being
controlled thereby, a signal rectifier device, sharp
ly tuned coupling means connected between said
rectifier device and said amplifier stage to apply
signals to> said rectiñer device in a frequency band
relatively narrow with respect yto the frequency
response band of the signal channel of the Vre
ceiver, a tuning indicator tube having a controlV
grid coupled to said rectifier device to receive a
portion of the direct current potential therefromV
resulting from signal rectification, a potential
divider device in said connection, and means for
opening a> connection with said device thereby to
vary said potential on said tuning indicator de
vice, said last named means being operative in
response to predetermined wave band change
in said receiver.
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