US 1937099 A
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Description (OCR text may contain errors)
NOV. 28, 1933. w s STEWART 1,937,099
RADIO RECEIVING APPARATUS Filed NOV. 5, 1927 90 Volts 6 225mm 5 Jvzz/emr.
Patented Nov. 28, 1933' iv i UNITED STATES PATENT O a 1,937,099 RADIORECEIVING APPARATUS William Scott Stewart, Chicago, Application November 5, 1927. Serial No. 2311189 v '5 Claims. (01.250 40) i The present invention relates to a simplified densers of varying'range, sotha-t-one ormore form of tuning control for radio receiving appamay be bridged across the'circuit when lower ratus that allows of practically instantaneous frequencies than may be attainable with only change from one frequency to, another without one condenser are to be received. Also any of the necessity of carefully adjusting dials and. these condensers may have aidefinite and-fixed 6Q; other control devices associated with such appacapacity. -j 7 j r a j v ratus; and which lends itself to ready operation This arrangement alsogreatly increases the by even such persons as are unfamiliar with radio frequency range of the receiver to "which my instruments. present invention is. applied, as obviously the 1 One of the objects of the present invention lowest frequency to which the receiver. may be is to provide a number of complete, but indetuned will be that attained when all the conpendent, tuning units for the radio receiving set. densers are thrown across the, inductance .coil, These tuning units are capable of being thrown and the highest frequency will be that when into and out of service by the mere throw of none of the condensers are thrown-across the a switch, and are independently adjustable so coil. For practical purposes, and to producea 70 thatany one of the said tuning units may be receivingsethaving the powerto receive electric I adjusted for a particular frequency. waves froma long distance, and to produce suffi.--
It is the usual modern practice in radio recient power to allow the use of loud-speaking ceiving sets to control the frequency to which devices, it is usual to employa number of stages the set will respond, or mother words the waveof amplification at high frequencies before, the 75,.-
length, by varying the inductance and capacity detector stage, such-amplification beingy com-w of the circuits associated with the amplifier and monly termed radio-frequency amplification-V detector tubes or other electric wave detecting Receivers incorporating such radio-frequency devices. Thismay be accomplished by a number amplification usually have two stages of this of different methods, as for example by varying amplification, followed by a. detector stage, the
the inductance, as by use of a variometer or by signals obtained from the latterstage thenxbeing some device capable of changing the number of passed eitherthrough" a telephoneinstrument-or' coils of a solenoid or similar coil, by varying the further amplified at lower, or audio frequencapacity bridged across such coil, as by the use cies to operate the loud-speaking devicesalready 6.0 of a variable condenser; or by varying both the referred to; In accordance with-,mypresent-in- 86 inductance and the capacity. vention, no change is made in the audio-fre- In the course of the development inthe art quency parts of the receiving. set. of constructing radio receiving apparatus, it has A further object of myinvention is to provide 7 become standard practice to adjust the frequency, means whereby a radio receiver may be. tuned 235 or, in more popular terms, to tune the reto a givenfrequency by one of the condensers 90 ceiver by employing coils of fixed inductanceuand that is bridged across the inductance coil by to tune the circuit associated with said coils and closing a'switch, whereupon the said' switch may detecting and amplifying device by' means of be opened, and asecond-switch connecting a variable condensers bridged across such coils. second condenser may be' brought into service,
49 In accordance with my present invention 1 and this second condenser may then be tunedgto v provide an inductance coil for each amplifier afrequency different from that ofthefirstconelectron tube and for the detector tube, but in- 'denser; and this may be repeated asmany times stead of bridging such inductance with but one as thereare condensers provided. This makesit variable condenser, I do so with a plurality of possible to tune the receiving settoa plurality.
i5 condensers, allhaving the same capacity and of sending'stations, any of which may be incharacteristics, any of which condensers may be stantly tuned-in by throwing the corresponding thrown out of service by means of a suitable switch connecting the condenser that isadjusted switch. It is contemplated to use but one of to tune in that particular frequency. n these condensers at atime, and each one of In sets using'a number of tuning units that -50 them is therefore chosen of such capacity range are cascaded, as for example insets using, two .105
that all of the desired frequencies, to-which the stages of tuned radio-frequency amplification receiving setincorporating my presentinvention and one tuned detector stage, it.has becomecuswill respond, may be attained by the use of but tomary to provide a condenserwforeaeh.ofithese one of these condensers. 7 However, it will be stages. Formerly these condensers were; inde- 55 within the scope of my invention to have conpendently variable, but the most modernconlglO struction is to vary the capacity of said condensers simultaneously. This is accomplished by either connecting the rotors of such variable densers, each set, for example, consisting of three variable condensers having their rotors mounted on a common shaft, and each of which individual condensers is electrically connected with a suitable inductance coil. Each of these sets of condensers may be thrown into servicebya suitable switch. Provision is aiso made for locking the individual sets of condensers in the position at which any desired frequency is tuned in at its maximum response, so that accidental displacement of the condenser setby accidental movement of the dial or tuning-drum may be avoided. a In the drawing accompanying the present application there is shown in Figures 1 and 2 a diagram of a standard radio receiver having audion tubes. The -audio-frequency amplification associated with the receiver is not shown, but merely indicated, as this forms no part of my present invention. a
In this drawing, Fig. l is a diagram of the cirouits employed, showing a plurality of condenser setsbridged across suitableinductance coils, and showing the switches employed'for throwing the various condenser sets into the circuit.
Fig.2 is a top plan view showing one form of switchthat maybe employed for connecting the condenser sets, when'the switch is closed; and 5 Fig. 3 is a similar View showing the switch opemand. 7
Fig. 4 is a detail View of the condenser and dial arrangement; A
either directly to the ground 5, or through a variable condenser 6 shown in dotted outline.
One side of'the secondary coil 3-is connected with the grid of the first radio-frequency amplifier electron tube 'l, and the other side of the coil to one of the leads of the filament of thesaid electron tube, as is well understood in this art.
The plate of the first electron tube '1 is connected to the primary 3 of a second radio-frequency R'I'z, whose secondary 9 is connected to the grid and filament of a second electron tube 10 in the same manner as the J connections of electron tube 7. The plate of the second electron tube 10 is connected with the primary ll of a third radio-frequency transformer RTs, and
- thesecondary 12 of the said transformer 3T3 is connected tothe grid of the detector tube 13,
a small capacity grid condenser and grid leak 14 being employed in accordance with the'wellknown principles of the radio receiver construction art." The plate of the detector tube 14 is connected with the primary of an iron-core audiotransformer AT1 inthe usual fashion, which requires no description, as this is'now standard practice,- and forms'no part of the present invention. I
The secondaries 3, 9 and Bare bridged by a plurality of condensers C1, C2, C3, C4 and Cs; ca 02a etc; and Clb, Czb etc. as shown on the drawing (Fig. 1), and switches S1, S2 and S3 are provided to connect such condensers across the said secondaries. It is to be understood that the condensers C1, Ca and Clb are on a single shaft and are therefore variable simultaneously. The same is true or" condensers C2, C22. and C2b, and of the othercondensers bearing the same series of numbersas C3, (33a and Cat etc.
. One side of the said condensers, and preferably the stator side, if rotary condensers are employed,
' is permanently connected to thefilament return side of the said secondaries, and the other, preferably'the rotor side, connected to one terminus of the switches' in order to throw any one set of three condensers into the circuit, a switch having the general form shown in Figs. 2 and 3 may be used, although it is within the scope of my invention to use any other form of convenient switching arrangement. I
In Figs. 2 and 3' it will be seen thatI provide a non-conducting shaft 15 having three conduct-'- ing knife-blades l6 capable of engaging suitable prongs The be con'tr ed by a dial oi'handle l8, and the said shaft may pass through the panel 19. Wires 20 and 21 serve to connect the switch terminals with the second. coils 3, 9 and 12, as already explained. A set of set of condense: five in the present case.
The operation of a radio receiver constructed in accordance with my present invention is as follows: 1
15 is rotatable and may switches provided'for each Supposing for example that the switch controlprinciples, and as shown diagrammatically in Fig.1, the receiver may then be tuned to a given frequencycorresponding to that of the sending stationthat is to be tuned in, for example one sending on a frequency of 979 kilocycles, and
which will for convenience be designated as Station A. This will correspond to a certain dial setting on the dial or drum-associatedwiththe shaft of the rotor of the condenser set then in use, namely condensers C1, C15 and Clb. When the maximum clarity and volume of signal is tuned in for station A, then a suitable set screw is tightened down against the dial or drum of the said condenser so as'to prevent the accidental detuning of the said set of condensers, One method of accomplishing this is shown in Fig. 4, in which the rotors of the condensers C1, C15. andCib are shown mounted on a common shaft 22, rigidly connected with a'dial 23 passing through a panel 23-1. A suitable bracket 2 L mounted on the said panel and bent so as to slightly cover the said dial 23 bears a screw 25 having a milled head 26:, and
by turning the said screw the dial 23 maybe locked into position.
If thereupon the switch associated with condenser set 01, Cm and Clb is opened, and the switch say StationBfsending on a frequency, for example-of 6 H) kilocycles. Thereupon, in win,
this condenser may be thrown out of the circuit ,by opening its switch, "and one of the other condenser sets may be thrown into service and tuned for their particular station. I
It will be seen that the setting for Station A,
on condenser set C1, etc., will remain unchanged, and the user of the receiver may return to the setting for Station A merely by throwing in the required switch associated with the said condenser. This makes the operation of a receiver incorporating my present invention very easy, for after the set has been tuned for the stations that are to be received, any one may tune'in any of the given stations by the mere throw of a switch. This is particularly valuable when the receiver is to be operated by inexperienced persons, when the tuning may be done by an experienced operator, and the condenser setting thereupon locked. All that the inexperienced user then needs to know is the number of the switch corresponding to the station that is to be tuned in.
Any number of independent condenser circuits may be introduced into the circuit, although only five are shown, as this is purely a matter of convenience. The regular operation of the set is in no way disturbed, as four of the condensers may be permanently set for four different stations,
and the fifth one may be used for tuning any de- I sired station, even including those that are permanently tuned in, so that it becomes possible, for example, to employ the time between the numbers of a program that is being received to listen to other stations, and then instantly to return to the regular program without changing the setting of the adjusted condensers. Obviously, the condensers to be set permanently may be of the fixed type, and I am not to be limited to the use of variable condensers throughout, nor to the particular types of variable condensers, as types other than those having rotors and stators may be employed.
Obvious modifications of the arrangement shown are to be understood as being within th scope of my invention.
What I claim is:
1. In a radio receiver a plurality of, sets of,
ganged condensers, simultaneously variable by a single control, each set being independently variable, inductances common to all of said sets of condensers, and means for selectively electrically connecting said sets of condensers with said inductances.
2. In a radio receiver a plurality of sets of ganged 1 condensers simultaneously variable by a single control, each set being independently variable, inductances common to all of said sets of condensers, means for selectively electrically connecting said sets of condensers-with said inductances, and means for preventing the accidental variation of the setting of the said sets of condensers. p
3'. In a radio receiving set means for perma- 'nently tuning said set to a given number of sende ing stations without impairing the ability of said set to be tuned to stations other than those to which it is permanently set, which comprises in- I ductance coils, sets of ganged variable condensers each set varied by a single control and being, 7 bridge across said coils for tuning said coils to anyfrequency within the. range of thecombination of said coils and said sets of condensers,
means for connecting and disconnecting the incuit changing devices'for introducing any one of the sets of condensers into said circuits.
' 5. In a radio receiving set having a plurality of inductance coils and associated circuits, means for selectively tuning said coils to aseries of fixed frequencies, comprising the combinationv of a plurality of sets of ganged condensers simultaneously variable by a single control, and means for connecting anyone of the said sets of condensers into the system as a unit by suitable switchin means.
, WILLIAM SCOTT STEWART.