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Патент USA US2124211

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July 19, ' 1938-
w. VAN B. ROBERTS
2,124,211
COMBINED AMPLIFICATION AND TUNING CONTROLS
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Filed Oct. 17, 1934
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INVENTOR
- 114417519 #4” I._ #085973”
BY /
‘
ATTORNEY
2,124,211
Patented July 19, 1938
UNITED STATES PATENT creme
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1
2,124,211
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,
COMBINED AMPLIFICATION AND‘ TUNING ‘
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' CONTROLS
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‘ Walter van B. Roberts, Princeton, N. J., as's‘ignor
to Radio Corporation of America, a'corporation ,
v of Delaware
Application October 17, 1934, SerialNo. 748,610
- ' . 1 claim;
(01. 1795-171)
My present invention relates to uni-controlled
tuning and ampli?cation control adjustments for
radio receivers, ‘and more particularly to novel
and improved devices for'correlatingpthe ‘tuning
5 ‘ and radio frequency energy transfer character
istics of the selector networks of radio receivers.
One of the main objects of my present inven
tion is to provide capacity coupled radio frequen
cy ampli?ers wherein the'capacity coupling exists
connection with the drawing in which IIhave in-,
dicated diagrammatically several‘ circuit organi
zations whereby my invention may be caried‘intoi
effect.
In the drawing:-—
‘'
Fig. 1 shows a circuit diagram ofra. radio freev
quency ampli?er embodying the ‘invention, and’
Fig. 2 shows the circuit ‘diagram of the ampli-i ,
?er embodying one mechanical form of a come, 1
10 between‘a following tunable radio, frequency se
bined tuning and ampli?cation control'device. :. ':
transfer characteristic and the tuning character
ferent ?gures designate similar circuit elements,‘
lector network and a'vpreceding non-tunable plate
‘circuit of a radio, frequency ampli?er; the energy
istic of the coupled circuits being varied in such a
15 manner, and by such devices, that a predeter
mined transfer characteristic over the entire tun
ing range‘is secured with the capacity coupling
as small as possible at' the high frequency end
of the tuning range, ‘and as" large as convenient
20 at the low frequency end.
,
Another important object of the invention is
Referring now to the accompanying draw
ing, wherein like reference characters in the dif—'
the radio frequency ampli?er of Fig. 1 shows a
pair of- screen grid tubes I and 6 capacitatively 161
coupled by a condenser‘ C. The input electrodes,
of ampli?er tube 1 may be considered arranged.
for coupling to any source of signal energy. For
example, the ampli?er network of Fig. l'may be
considered as the radio frequency ampli?er of? a 20,
superheterodyne receiver. In such case the .out
to provide an adjustable capacity device between
put electrodes of tube 6 may be adapted for ‘con
the plate circuit of a radio frequency‘ampli?er
and.’ a following tuning circuit, the adjustable
nection to the‘ ?rst detector of the set, or the tube
6 may itself be the ?rst detector“ Of course,‘ the
signal collector. may, in that case, be‘ connected
to the input electrodes of ampli?er l, and a tun
able selector circuit may be connected to the
25 capacity device mechanically cooperating with
the variable tuning condenser of the tuning cir
cuit to provide an adjustable capacitycoupling
between the preceding plate-circuit. and the fol
lowing tuning circuit, and the variation of the
30 capacity coupling being so related to the varia
tion of the following tuning condenserthat a
desired, energy transfer characteristic is - secured.
Another object of the invention is tov provide
input of ampli?er
I.
a
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If the ampli?er network is in areceiyer of the
tuned radio frequency type, then the ampli?er I
may be the ?rst tunable radio frequency ampli
?er, and the tube 6 may be the'second- tunable
30,"
radio frequency ampli?er, or it may be the de- y
In any case the present invention is‘to
be understood as havinga wide applicability;
a novel type of tuning condenser for they tunable
35,v selector circuit of a radio frequency ampli?er, the
tunable circuit being arranged for coupling to
the untuned plate circuit of a preceding ampli
tector.
an auxiliary ‘condenser effectively connected
40 across the untuned plate circuit, and an auxiliary
pair of rotor plates being provided on the rotor
quency energy transfer characteristics of the
coupling network so as to obtain a desired energy‘
transfer characteristic over the tuning range of
whatever the nature of the circuits which are
coupled, the problem to be solved by the present
?er, the tuning condenser being providedwith. invention is tovary theqtuning and radio fre-'
shaft.
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the receiver.
_
provide especially simple and‘economical devices
The plate of ampli?er l is connected to the low
potential side of the usual grid biasing network 2'
through a path which includes the radio fre 4,5,
quency choke 3 and the source of plate voltage 4.
for securing a predetermined energy transfer
The frequency selection network ‘ comprises the
characteristic over the tuning range of a radio
coil 5,and the variable tuning condenser t connect:
Still other objects of the invention are to im
prove generally the efficiency of radio frequency
45 ampli?er networks of the tunable type, and to
, ed, in shunt with the coil 5; the tunable circuit be‘
The novel features which I believe to be char; ing connected in series between the input grid ofv ,
50
tube 6 and the low potential'side of the grid bias
acteristic of my invention are set forth in par
ticularity in the appended claim, the invention ing network ‘I. The coupling condenserlC con
frequency ampli?er.
itself, however, as tov both its organization and
method of operation will best be understood by
55 “ reference to the following description taken in
nects the plate side of choke 3 to the high alter
nating voltage side of the following tunable cir~~
cuit. The problem presented for solution bylthe
2
2,124,211
invention of the present application is to vary
the tuning of the tunable input circuit of tube 6
over the tuning range of the receiver, and yet
necessary to show the side view of the condenser
plates, or the housing construction of the plates
maintain a desired and predetermined radio fre
of the manner of constructing such condensers
quency energy transfer through the coupling con
denser C over the entire tuning range of variable
condenser t.
of the variable type.
The pro?le of the plates of condenser S are cut
to give any desired variation of condenser S with
respect to the variation of tuning condenser t.
because those skilled in the art are fully aware
Fig. 1 shows the manner of securing such a re
lationship, or rather such a correlation of tuning The two» condenser assemblies S and t are located
10 and energy transfer, and it is also accomplished , far enough apart on the shaft so that the stray 10
in a simple, effective and economical manner.‘
capacity between stators is smaller than the
An auxiliary condenser S is connected across the smallest‘value of coupling capacity desired at C.
plate circuit of tube I, and in shunt with con
The disposition of a grounded shield 8 between the
densers C and t. The magnitudes of condensers
adjacent stators l3 and I2 will reduce the re
15 S and C are so chosen, and their rates of varia- .1 quired separation, but the separation should not 15
tion are uni-controlled with the variation of con
be reduced too much, or the minimum capacity
denser t in such a manner, that a predetermined
of condensers S and t will be increased too much
energy transfer characteristic can be secured. by the close proximity of their stators to the
Such a characteristic may be of the uniform, or grounded shield 8.
20 ?at, gain type; that is to say, the ampli?cation
The variable capacity C consists of the metal 20
of the signal energy will be substantially uni
form over the tuning range of the receiver em
bodying the ampli?er network shown in Fig. 1.
To preserve as large a tuning range as possible,
25 say over the broadcast band which is between 500
and 1500 kilocycles, the value of condenser C
should be as small as possible at the high fre
quency end of the tuning range of the receiver;
it should be as large as ‘convenient at the low fre
305 quency end. It is not believed necessary for the
purposes of the present application to present the
theoretical considerations which support the pre
mise that for a given set of other conditions‘, the
value of condenser C required for a given am
pli?cation depends upon the value of condenser
S; It will be sufficient to point out that such a
premise is established in an analysis entitled
“Maximum Ampli?cation In Capacity-Coupled
Circuits”, ‘appearing on page 20 of Electronics for
40 July, 1931.
It can now be stated that it is the purpose of
sulation material l0, such as a collar of insula
tion material, is carried by the shaft 9, and the
bolt‘ I5 is disposed within the collar.
'
of plates 16, l?'iwith rotors l4 and H. Plate I6 30'
is disposed adjacent the end stator'l2 of condenser
15, while plate i6’ is disposed adjacent the end
stator I3 of condenser S. The plates l6’ and Hi
cooperate with their adjacent stator plates to
provide the condenser C. Hence it will be seen 35"
that as'shaft 9 is‘ varied the capacity values of
condensers S, C and t are varied. The conductor
comprising plates l6 and I6’ is not electrically
connected to any portion of the circuit,'but serves
to vary the effective separation between the sta- ,'
tors of condensers S and t. The blade pro?les of
the present invention to vary the capacity value
the conductor element Iii-I6’ are also cut to
give any desired variation of capacity C with re
spect to the'capacities t and S. In other words,
the capacity between the adjacent end stators of
condensers S and t constitutes the capacity which
couples the high alternating potential side of con
45 be required to assume a small value at the high‘
frequency end of the tuning range and arrelative
ly large value at the lower frequency end. In
Fig. 1 the dotted lines U designate the mechanical
uni-control arrangement for varying the three
50 condensers. This mechanical variation of the
condensers should, of course, be accomplished in
an economical, effective and simple manner, and
without the use of sliding contacts or “pigtail”
connections.
In Fig. 2 such a mechanical construction is
shown. The normal condenser construction is
utilized for the condensers S and 15. That is to
say, rotors l4 and II are mounted on the uni
control shaft 9; stators l2 mesh with rotors H,
60 and stators 13 mesh with rotors M. The capacity
provided between plates I3 and I4 is connected to
provide the condenser S, while the capacity be
tween plates l2 and II furnishes the tuning con
denser t.
It is to be understood that the well known type
65
of “bathtub” gang condenser may be utilized for
‘this purpose, and the shaft 9 will be understood
as additionally being connected to, and support
ing on it, the rotors of the tuning condensers of
70 other ampli?er stages. The auxiliary plates l4"
and I3 may be used in conjunction with each
tuning condenser of each stage. For the pur
pose ofsimplicity, however, the construction be
tween a given pair of ampli?er tubes is only con
sidered. It will also be understood that it is un
25
The collar I0 is rigidly connected to shaft 9 so
that adjustment of shaft 9 results in movement
of condenser S in such a fashion that for a desired
ampli?cation characteristic the condenser C will
55
conductor composed of two plates l6, l6’ metallic
ally connected together by a bolt l5. This con
ductor is insulated from shaft 9, although me
chanically adjustable therewith. A block of in
denser S to the high alternating potential side‘
of the tunable circuit of ampli?er 6. The value
of this inter-stator capacity is varied by the plates 50
It and I6’, and the disposition of these plates be
tween the adjacent end stators is varied at a rate
dependent upon the rate of variation of the ca
pacities of condensers S and t. It is not be
lieved necessary to go into any further detail con 55
cerning speci?c pro?les for the blades of the
condensers, since such pro?les can be easily de
termined by those skilled in the art when it has
been decided what. the ampli?cation character
istic is to be; As stated before a speci?c type of 60
such characteristic is one that is uniform over
the receiver tuning range, and in Fig. 2 it is to
be understood that the capacity’ values of con
densers S and C are varied with the variation of
condenser t so that the transfer of radio fre 65
quency energy to the output circuit of tube 6 is
substantially uniform over the tuning range of
the receiver. It will now be appreciated that this
relation of ampli?cation and tuning has been
secured in a highly economical and simple fash
ion,‘and without sliding contacts.
For a further disclosure of the manner of con
structing a variable condenser of the type shown
in Fig. 2, reference is made to application Serial
No. 387,148 of J. L. Bonanno, ?led August 20, 1929,
3
2,124,211
issued as Patent No. 2,040,426 o'nMay 12, 1936,
wherein there is claimed, as well as disclosed, the
organizations shown and described, but that many
modi?cations may be made without departing
type of variable condenser shown in Fig. 2, and ' from the scope of my invention, as set forth in the
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the manner of varying the inter-stator capacity appended claim.
provided between adjacent variable condensers
using a. common rotor shaft. In the above Bon
anno patent the variation of the inter-stator
capacity is used to vary the coupling between a
pair of coupled tunable circuits of a band pass
.10 network; in the present application the variable
condenser construction of the Bonanno patent is
What I claim is:
V
,
In combination in a high frequency network
which comprises a ?rst tube having an untuned
plate circuit‘ which includes a radio frequency
choke and a shunt capacity, a second tube pro
vided with a tunable circuit, a condenser coupling‘ 10
the plate circuit of the ?rst tube to the tunable
used to secure ‘a predetermined ampli?cation , circuit, and means including a common control
characteristic over the tuning range of the re
ceiver.
15
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While I have indicated and described several
for simultaneously varying the value of said
shunt capacity, coupling condenser and the tun- '
ing condenser of the tunable circuit whereby a 15
systems for carrying myinvention into e?ect, it
uniform energy transfer is‘ obtained over the
will be apparent to one skilled in the art that my
tuning range of the network.
invention is by nomeans limited to the particular
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WALTER VAN B. ROBERTS.
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