US2447490A - Radio transmitting and receiving system - Google Patents

Description

Aang 24, 394% K A. ACOLLINS- 2,447,49@

RADIO TRANSMITTING AND RECEIVING SYSTEM Filed Feb. 28, 1944 2 sheets-sheet 2 Patented Aug. 24, 1948 RADIO TRANSMITTING AND RECEIVING SYSTEM Arthur A. Collins, Cedar Rapids, Iowa, assigner to Collins Radio Iowa Company, a corporation of Application February 28, 1944, Serial No. 524,204

This invention relates to a radio transmitting and receiving system, and more particularly to a system ensuring transmission and reception on the same frequency.

One feature of this invention is that it provides an improved radio transmitting and receiving system; another feature of this invention is that a single tuning means effects coordinated selection of a desired frequency in both the transmitting and receiving portions of the system; still another feature of this invention is that transmission and reception always take place on the same frequency; and yet another feature of this invention is that the system is readily tunable to any desired frequency in any of a plurality of frequency ranges. Other features and advantages of this invention will be apparent from the following specification and the drawings, in which:

Figure 1 is a lblock diagram of a system embodying my invention; and Figures 2a, and 2b comprise a circuit diagram of an operable embodiment of a transmitting and receiving system corresponding to the diagram of Figure 1.

Two-way radio communication is becoming of increasing importance, and under many circumstances it is desirable to have the transmitting and receiving equipment tunable over a desired frequency range, or a plurality of frequency ranges. Under such conditions the transmitted frequency cannot be crystal controlled, but must have a frequency controlled by a tunable oscillator tank circuit. Despite the greatest care in design and construction, an oscillator tank circuit undergoes frequency changes as the result of its exposure to variations in temperature, humidity, etc., and this makes it difficult to determine accurately, by any system of dial calibration, the frequency being transmitted or received, particularly in the higher frequency bands, as those used in aircraft work.

I have devised and am here disclosing a singlecontrol radio transmitting and receiving system wherein transmission and reception on the same frequency are ensured. This enables an opera- Claims. (Cl. Z50-13) transmitting and receiving systems of types devised by other research men collaborating With me on this problem, these other systems being the subject matter of other ,copending applications of Frank M. Davis (Serial No. .524,205, filed February 28, 1944, now Patent No. 2,402,606, issued June 26, 1946; Serial No. 548,978, filed August 11, 1944; and Serial No. 685,934, led July 24, 1946), broad claims to systems of this type being included in the second mentioned Davis application, and Melvin L. Doelz (Serial No. 524,206, filed February 28, 1944).

My system comprises, as its principal elements, Wave generating means variable over one or more predetermined frequency ranges, as a tunable oscillator with or without associated frequency multiplying means; means for amplifying and transmitting waves of a desired selected frequency in any of said ranges; means for displacing the frequency o-f the Waves a given percentage (rather than a given frequency), regardless of the frequency to which the Wave generating means may be tuned; and a superheterodyne receiving system having an intermediate frequency amplifier tunable over bands corresponding to the difference between the initial and displaced frequencies of said waves throughout said ranges, tuning of the oscillator and the intermediate frequency amplifier being ganged or coordinated for operation by a single tuning control, and the displaced Waves serving as the local vheterodyning waves for the receiving system. When one has ceased transmitting, rendering the displacing means and receiving system operative, without touching the tuning control, ensures reception on the exact frequency being previously transmitted; and conversely, when another signal is being received, switching to transmission ensures sending on the exact frequency of the signal previously heard.

While I am terming the system disclosed here a single-control system it will be understood it is meant that there would be only a single tuning control for both the transmitting and receiving portions of the system, which would normally be housed in a single cabinet. In addition, of course, there would be a band switch, antenna coupling and loading controls, an on-off switch or several of such switches, and generally a manual volume control for the receiving portion of the system. The switch-over from transmission to reception would normally be effected by a, keying relay, or by a push-button-operated relay associated with the microphone of the transmitter. With a system of this kind, no matter how inexperienced the operator may be, once he nds and hears a given station (whether it be another airplane, a ground station, or the like) he is sure to be able to talk to it, sure to be on the frequency to which the receiver of that other station is tuned. Another advantage, claimed in one of the other co-pending applications, is that the same antenna tuning and loading circuit may be used for coupling both the transmitter and receiver to the antenna, so that the antenna can be tuned during reception, without breaking radio silence, with assurance that transmission will be at or very near maximum possible power without loss of time for adjustment'of the antenna tuning and loading controls aftertransmissionIhasl been started.

In the particular embodiment of my system illustrated herewith, and referring first more particularly to the block diagram, Figure 1, a tunable oscillator A delivers its output to a multiplier B ,these comprising means for generating waves of any desired selected frequency in any of a plurality of bands; the-multiplier being adapted to provide various multiplications. The output of the multiplier B is connected to the moyableaelement of a two-position switch B (shown in the transmitting position in dotted lines and in the receiving position in solid lines), being delivered to the power amplifier C during transmission; and the amplified carrier is modulated in conventional manner vby a modulator E. In the position of the switches shown in dotted lines in the drawings, the modulated output ofthe amplier C is connected through the switchv Cf to the antenna lter circuit D, or antenna tuning and loading circuit, this being in turn-connected to the antenna and to ground. This arrangement comprises a conventional tunable transmitting l system.

The switch Afis adaptedto connecta fixed" reactance element (as the fixed condenser shown) into the tank circuit of the oscillator, and to disconnect it therefrom, to displace the frequency a given percentage; and the switches ation of the frequency displacing switch A- causes the frequency of theoscillator to be displaced a given percentage, as for example and the multiplied frequency, of course, retains this same given percentage displacement; With the switches set for reception, the output of the multiplier is delivered to the lteroircuit F, which is tunable and passes only the displaced frea. quency; the antenna and 'its associatedlrfllter or tuning circuit are connected through the switch C' to the input of the radio frequency amplifier G, and the output of this'radiofrequencyamplii'ier G is delivered to the mixer or first detector stage H where the displaced wave fromV the wave generating means, delivered through the filter circuit F, serves as the` local heterodyning wave to Abeat the incoming signal down to Van intermediate frequency. The reduced frequency signal is delivered to the tunable intermediate frequency amplierJ and then passes through a. second detector K and an audio amplifier L and is delivered to earphones, or some-other translating-meansSoot'showpi; f f

The difference between the desired incoming signal and the displaced frequency wave delivered by the wave generating means varies (in the sense of absolute frequency) as the result of variations in the frequency of the wave generating means, and to take care of this intermediate frequency variation the intermediate frequency amplifier is made tunable. As illustrated in the block diagram, the tuning controls of all of the tunable portions of the system are ganged. 'I'he gauging and tracking of the intermediate frequency amplifier tuned circuits with the oscillator tuned circuit is not at all difficult, since no attempt is being made to maintain a fixed frequency difference, which presents problems in accurate tracking, the displacement or local heterodyne difference being a fixed percentage. It will'be understood, of course, that the various tuned circuits are provided with different elements adapted to be switched in when different bands are to be covered, the coordinationlbeing effected by the tracking Vof-the variable reactance elements, and remainingA undisturbed by the addition or subtractionv of fixed reactance of the opposite character.

For the purposes of this description it will be assumed that the oscillator A is so designed as to be variable over a range of 1,000 to 1,500

kc. during transmission; and that operationof' the frequency displacing switch A'.' (effecting removal of a portion of the fixed capacityfrom the tank circuit) results in the oscillator'tuning from 1,100 to 1,650 kc. vduring receptionfa 10% displacement. understood that the word displacement isintended broadly to cover either an yin'crease'or decrease `of frequency throughout the rangepand that it can be accomplished by removalfor ad-1 dition of fixed reactance to Ith'e'tank circuit.

For convenience of description, the frequency' usedA on transmission is being termed Mthe "'initial ordesired frequency, and the Vdifferent frequency used for localheterodyning purposes is being termed the displaced frequency.

If the multiplier portion B of the [system is arranged rfor doubling, transmission may beon any selected frequency in the range of 2,000' to 3,000 kc., double the oscillator frequency varia'- tion; and for purposes of illustration it may be output of the multiplier B being displaced fromv 2,000 to 2,200 kc. Y

I On this bandthe intermediate frequency amplifier would be arranged to bel tunable from 200 to 300 kc., its tuning. being coordinated with that of the oscillator, s o thatV with the oscillator at the 1,000 kc. setting, the intermediate frequency amplifier would Abe tuned to. anintermediate `frequency of 200 kc.-ljl se of Vthe displaced frequency of 2,200 kc., therefore, as the local heterodyne frequency, results in; only ;signalsof 2,000 or 2,400 kc. being beat to this intermediate frequency of 200 kc.; and the v tuned circuits in the radio frequency portion of the receiving system would eliminate the 2,400 kc. signals in the antenna, if any, so thatunder these conditions the frequency receivedwould be 2,000 kc., the same frequency as thatntransmitted. While this has been describedas'though transmission were first, it will be understood that if the system hadbeen in condition for reception@ ami-'tuned i0 .a 2,009.1{6- desired signal, throwing- In this regard, itW-wil'lb'eV the system over toA transmission would resultj in transmission vonthe same frequency; `andthis,

would be true regardless of whether the oscillator frequency had Varied from any arbitrary calibration vof thedial, since tuning to the desired signal would necessarily-bring the oscillator tol the desired frequency, regardless of the dial calibration.

The system can be arranged to provide singlecontrol tuning for as many other bands as may be desired. For example, arranging the multiplier to treble the oscillator frequency results ina transmission frequency anywhere in the range of 3,000 to k4,500kc. displacement resultsin a displaced frequency in the range of 3,300 to 4,950 kc.; and switching the intermediate frequency tuned circuit constants would cause these tuning circuitstocover the range of 300 to 450 kc.` on this second band. Again, quadrupling would give a transmitting frequency anywhere in the range of 4,000 to 6,000I kc.; a displaced frequency of 4,400 to 6,600 kc.; Vand the intermediate f requency amplifier would be arranged to tune from 400 to 600 kc. Two stages of multiplicationmight then be used, one doubling and one tripling, resulting in a transmission frequency range from 6,000 to 9,000 kc.; a displaced or local heterodyningfrequency of 6,600 to 9,900 kc.; and this would be used with an intermediate frequency tuning range of 600 to 900y kc. In each case all of the tuned circuits wouldhave a tuning range of 1.5 to 1, and the shape of the tuning curve would not be important, it only being necessary thatA the curves be the same in the various circuits. c v,

Referring now more particularly to the circuit diagram of Figure 2 (comprising portions 2a and 2b), the portions corresponding tothe Various rectangles of the block diagram of Figure 1v are similarly lettered. The oscillator A is shown as comprising a tube lil, which may be tube type No. 12SJ7, having v a v tank circuit comprising a permeability tuned variable inductance il, a fixed condenser I2 permanently in circuit, and an additional fixed condenser I3 adapted to be connected to or disconnected from the tank circuit by the displacing switch A'. While the various tuned tankcircuits throughout the system are shown `as having fixed condensers (exceptfor such slight variations as may be desirable for trimming) and variable inductances, it will be understoody that the principles are equally applicable to circuits where the inductances are xed and tuned by variable condensers, displacement being eifected in either case by a small fixed rea-stance of the same character as the main xed reactance.

The output of the oscillator is coupled to ther multiplier, here shown for simplicity of circuit illustrations as comprising a single tube, iii, which may be tube, type No. 1,2A6, although it will be understood that in commercial practice two such stages ofmultiplication would normally be used in cascade. The output4 of the multiplier has two tuning combinations associated therewith, comprising two sets of fixed condensers Nia-d and` iSd-0l adapted to be selectively associated with the tunable coil I1. denser is selected by the band switch, shown connected to the condenser a, to select the rst band, the other condensers lh-d being selected, respectively, for bands 24-4. When the system is thrown over to receiving condition, the switch B renders a condenser of the group I6 operative, the-combination of thesecondensers With An appropriate con-r the coil I1 then forming part of the filter circuit delivering displaced waves to the mixer of the super-heterodyne portion of the system, where they are operative as the local heterodyning` waves.

When transmitting, the output of the multiplier B is delivered to the power amplifier here shown as comprising the tubes it and IB, which may be of tube type No. 1625, and which would in commercial practice be preceded by a preamplifier stage and a driver stage, for example, these being omitted for simplicity. The space current in these tubes would be modulated by power derived from the modulating portion of the system, shown in the upper half of the sheet identified as Figure 2b. This is here shown as comprising a jack 20 adapted to have a microphone or keying means connected thereto, this being coupled to a driver tube 2l, which may be tube type No. 12A6, in turn transformer-coupled to modulator tubes 22 and 23, which may be 1625 tubes, the output of these modulator tubes aifecting both the screen and plate voltages of the power amplifying tubes i8 and l0, through the wires a and b. A lead from jack 20 to the cathodes of modulator tubes 22 and 23 provides D. C. actuating supply for the microphone or keying means, and has incorporated therein a reactor which blocks A. C. from the cathodes of the modulator tubes. An A. C. path from jack 20 to ground is provided by the condenser 5l connected between the lower end of the primary of the input transformer and ground.

The modulated output of the power amplifier C is delivered, when the change-over switch C' is in its upper or transmitting position, to the antenna tank circuit comprising the condensers 2d and the variable inductance coil 25. This is coupled, in accordance with conventional practice for a short antenna, to antenna loading means here shown as comprising a tapped coil 26 and a variometer 2i, the terminal 28 being connected to the antenna.

When the change-over switches place the system in receiving condition, the antenna tank circuit is connected, as shown in the drawings, through the wire c to the signal grid of the radio frequency amplifying tube 29, which may be tube type No. 12SK7, plate supply for the superheterodyne receiving system being then provided by a connection through the plate-supply change-over switch M', ganged with the switches A', B and C". The input of the radio frequency amplifier is, of course, tuned by the tank circuit here shown as associated with the antenna. The output is tuned by a tank circuit comprising any one of the four condensers 30 and the variable inductance 3l.

The output of the radio frequency amplifying section is coupled to one of the grids of the mixer tube `32; .while another grid of this tube is supplied, with the local heterodyning or displaced waves derived from the wave generating means comprising the oscillator A and multiplier B, these being delivered through the wire d' and coupling condenser 33. The mixer, in accordance with conventional practice, beats the signal frequency `down to intermediate frequency which, in the case of the first band on which the circuit is shown set, might be 200 to 300 kc., as assumed earlier.

This intermediate frequency output is delivered to an intermediate frequency amplier J here shown as comprising thetube 34, which may be tubetypeNo. 12SK7, it being understood that ang-40o commercially at least two similar stages of' suchl intermediate frequency amplification would be used in cascade. In accordance with 'convene tional intermediate frequency amplifier practice, both the inputs and outputs of a transformer coupling arrangement are tuned; but, contrary to normal practice, these coupled tuned circuits are tunable over a band, as the 200 to,300 kc. assumed in connection with band I. The input side of the intermediate frequency coupling arrangement is here shown `as comprising the variable coil and the condensers 36m-41. The condensers 36u-d are each connected, respectively, to the corresponding condensers of the group 31, and to ground through a group of condensers 38. That is, when the band switch is in position to cover the firsthand, condensers 36a and 31a would be connected in series, with their midpoint connected to ground through the condenser 38a, all of the other condensers in these sets being inoperative. The movable element of the band switch associated with the condenser 31 is connected to one end of the Variable inductance 39 to provide a tuned parallel ouput circuit for the intermediate frequency coupling arrangement. The purpose of using three sets of condensers is merely to provide a common reactance for coupling purposes.

The output of the tube 34 is delivered through another doubly-tuned coupling arrangement comprising the variable coils 40 and 4i and the associated sets of condensers 42, 43 and 44 to a detector here shown as 'a Asimple diodeY tube 45. In practice, however, this tube would usually comprise a five element tube, astube type No. 12SR7, having the Vtwo anodes connected together and the additional grid and plate elements used, in conjunction with `an appropriate tank circuit, to provide a beat frequency oscillator for code reception, this arrangement not being shown since the whole-circuit is illustrated, for'sirnplicity, merely as a voice system. The audio output of the detector tube 45 is delivered to an audio amplifying tube 45, which may be tube type No. 12SK'7, the output of this being shown as supplied to a jack 41 which is adapted to be connected to earphones, a speaker, or the like. In practice, the tube 46 would normally be followed by at least one additional power stage of audio amplification.

An operative circuit of the character described and for the bands or frequency ranges previouslyY assumed, might have the oscillator inductance II variable from 11 to 25 ahy.; the multiplier, antenlna tank circuit, and mixer inductances i1, 25 and 3| variable from 6.2 to 14 phy.; and the intermediate frequency primary and secondary in'- ductances variable from 176 to 400 ahy. Undei` these circumstances, the oscillator tank circuit principal condenser l2 might have a capacity of 825 mmfd., and the condenser I3 a capacity of 175 mmfd. The condensers; ISa-d, in the multiplier output when transmitting, might have a capacity of 450, 200, 112 and 50 mmfd., respectively; and these same values might be used for the condensers 24 and 30. During reception the condensers i6 would be associated with the coil i1 to filter the multiplier output, and these might have a value of 370, 163, 92 and 41 mmfd., re spectively. The intermediate frequency condensers 36e-d, and the similar condensers in the sets 31, 42 and 43, might have values of 1,600, '700, 400 and 175 mmfd., respectively, and the associated condensers of the sets 38 and 44 might havea value of .08, .04, .03, and .015 mfd.

lltlieit circuitconstantswould be of 'convert-5 tinar vaiue' for the lpasticciar tunes usedff'rhe coupling condensers between the 'tubeswand M and* vb'el'vve'eii the power:v` amplifier tubes 'and' the antenna tank circuit' might 'be .002`xnfd`;` coupling condensers between the multiplier tube l and the power 'amplifiertbea and those Aassociated with the tubes "29 and 32, might be .00l mfd:'; while that coupling the tube 45 to thetube 4B mightlbe al .1"mfd.,land thaton the input o f the oscillatr tube mmfd. The by-pass condensers in the transmitting and receiving por-v tions of the system might all be .002 mfd. except that -in the filament in the audior amplifier tube 46, and those associated with the' jiilaments of the driver and modulating tubes in thev modu' lating portion VWhi'ciifiriight be 42 0 mfcl.A The ,conf- .j

densers connecting the `intermediate Vffr eqiieilcy coils-'35, 39,10'arid4lto ground mightbencoaj mfd. The grid resistors Vin themultiplier and' power ampliler"would generally be 10,000 or 20,'000'olims`; the gridleak resistrsin the oscill-k lator, multiplier andaudio amplifier tubes about 50,00013mm;` that usedwith'the driver, tube '2l about EvlAymeg.; that used with Vthe tube 20 about 1- m'gij `and those associated With the signal grids of the mixer and intermediate amplifier tubes from 100,000 to 500,000 ohms. The'screen grid resistors used in this receiving portion of the system would preferably l'be o f ahi'gher value than` those 'use'din the transmittngportieri as for example 100,000 ohms. The Acathodel resistors Would'be from 200 to 500 ohms, depending upon the tubesand the prtions of the circuits; and other'circuit elements not' specifically described f would follow conventional practice in connectien'4 purposes"shownhere.A

While I have shown and described certainem- With the types 'oftubes namedin circuits for the abodiments of my invention, it ls to be'understood` that it is capableA of y'many modifications.

Changes, therefore, in the construction'and are, rangement maybe made withoutdeparting from Y the spirit and scope of 'thelnvention asdisclosed in the appended claims.

I claim: j l. Radio apparatus ofthe character described, including: wave generating means'variablefover a predetermined "frequency rangefmeans for amplifying and transmitting Waves of any selected frequency in' lsaid range; means forQdisplacing the frequency of the 'waves "a given per,-y centage ofthe selected frequency; and a super heterodyne receiving system having anv Aintermediate frequency amplier tunable over a'band corresponding tothe difference betweenthe initial and displaced frequenciesl of said Waves throughout said range and a mixer "deliveringits' output to the" intf'zrmediate frequency amplifier,

the displaced wavesservingas the local hetero?` .dyning waves' forsaid receiving system. f

2. Radio apparatus of thecharacter described,VV

including: wave generating meansvariable over a predetermined frequency range; means for amplifying and transmitting'tvaves of any s e lected frequency in ysaid 'range; means f or dis-, placing the frequency of the Waves a given per-l centage of the selected frequencyg-anda superheterodyne receivingsystem having an intermediate frequency amplifier tunable over a band corresponding to the difference between the initial and displaced frequencies, of said waves throughout isaidfrange, a mixer delivering its output to the intermediate frequency'amplifier, andv .means for oerdihetmsle redeneert@ geef erating `meai1s`with-the tuning 'of the intermedi" 9 ate frequency amplifier, the displaced Vwaves serving as the local heterodyning Wave-s for said receiving system.

3. Radio apparatus of the character described, including: Wave generating meansvariable over each cf a plurality of predetermined frequency ranges; means adapted to be connectedy to said generating means for amplifying and transmitting Waves of any selected frequency in any of said ranges; means for displacing the frequency of the waves a given percentage of the selected frequency; and a super-heterodyne receiving system having an intermediate frequency amplifier 4. Radio apparatus of the character described;

including: wave generating means variable over a predetermined frequency range; ymeans for amplifyingand ltransmitting Waves of any selected frequency in said range; means for displacing the frequency of the waves a given percentage of the selected frequency; a superheterodyne receiving system having an intermediate frequency amplifier tunable over a band corresponding to the difference between .the initial and displaced frequencies of said Waves throughout said range, a mixer delivering its output to the intermediate frequency amplifier, and'means for coordinating the variation ofthe generating means with the tuning of the intermediate; frequency amplifier; and selectivelyl operable means for connecting the wave generating means to the amplifying mean-s in one operative position and for actuating the displacing means and connecting the wave generating means to the mixer of the receiving system in another operative position, whereby the displaced waves serve as the local heterodyning waves for said receiving system and the received frequency is identical with the transmitted frequency.

5. Radio apparatus of the character described, including: wave generating means variable over a predetermined frequency range; power amplifying means for amplifying waves of any selected frequency said range; an antenna system comprising an antenna and tuning means therefor; means for displacing the frequency of the waves a given percentage of the selected frequency; a super-heterodyne receiving system having an intermediate frequency amplier tunable over a band corresponding to the difference between the initial and displaced frequencies of said Waves throughout said range, a mixer delivering its output to the intermediate frequency amplifier, and mean-s for coordinating the variation of the generating means with the tuning of the intermediate frequency amplier; and selectively operable means for connecting the wave generating means to the input of the amplifying means and the antenna system to the output thereof one operative position and for actuating the displacing means and connecting the antenna system and the wave generating means to the mixer of the receiving system in another operative position, whereby the displaced waves serve as the local heterodyning waves for said l 1G receiving system and the received frequencyv is identical with the transmitted frequency.

6. Radi-o apparatus of the character described, including: wave generating means variable over each of a plurality of predetermined frequency ranges; power amplifying means for amplifying waves of any selected frequency in any of said ranges; an antenna system comprising an antenna and tuning means therefor; means for displacing the frequency of the waves a given percentage of the selected frequency; a superheterodyne receiving system having an intermediate frequency amplifier .tunable over aplurality bands corresponding to the difference between the initial and displaced frequencies of said waves throughout each of said ranges, a mixer delivering its output t-o the intermediate frequency amplifier, and means for coordinating the variation ofthe generating meanswith the tuningfof the intermediate frequency amplifier; and selec-fV tively operable means for connecting the wave generating means to theinput ofthe amplifying: means and the antenna system tothe output thereof inone operative position 'and for actuating/the'displacingmeans and connecting the antenna ysystem andthe wave generating means to the mixer of the receiving system in another rativeposition, whereby the displaced yWaves serve as the localheterodyning waves for said, receiving system and the received rfrequ'encyki-s identical with thetransmittedfrequency@r y 7. Radio apparatus of the character described,vv including: Wave generating means Variable over, each-of a plurality of predetermined frequency ranges; said means including means, for `previding waves, of a frequencydisplaced agiven percentage from a selected frequency; ,aJsuper-heterodyne receiving systemhaving anintermediate frequency amplier tunablecver a plurality of bands'corresponding'to the difference between the selected and displaced frequencies of said waves throughout each of said ranges, a mixer delivering its output to the intermediate frequency amplier, and means for connecting said mixer to the generating means, whereby said displaced frequency waves serve as the local heterodyning Waves for said receiving system; and a single means for effecting coordinated variation of the rst mentioned means and tuning of the intermediate frequency amplifier.

8. Radio apparatus of the character described, including: an oscillator having a frequency ccntrolling tank circuit comprising an inductive element and a capacitive element in parallel, one of said elements being variable and the other fixed; means for effecting various predetermined different multiplications of the frequency of the Waves generated by the oscillator to provide a plurality of predetermined frequency ranges; means for displacing the frequency of the waves a given percentage of the selected frequency, this means comprising another reactive element of the same character as the fixed element and means for connecting this other reactive element into the tank circuit and disconnecting it therefrom; means for amplifying and transmitting Waves of any selected frequency in any of said ranges; a super-heterodyne receiving system having an intermediate frequency amplifier tunable over a plurality of bands corresponding to the difference between the selected and displaced frequencies of said waves throughout each of said ranges and a mixer delivering its output to the intermediate frequency amplifier; selectively operable means for connecting the Wave generating means to the amplifying means in one.I operative position and for actuating the displacing means.. selecting the intermediate frequency amplifier band in accordance with the predetermined multiplication effective, and connecting the Wave generating means to the mixer of the receiving system in another operative position, whereby the displaced waves serve as the local heterodyning waves for said receiving system; and a single means for effecting .variation of the variable element in the oscillatorv tank circuit 'and tuning of the intermediate frequency amplifier and for coordinating said variation and tuning.

9. Radio apparatus of the character described, including: wave generating means variable over a predetermined frequency range, this means including a frequency controlling tank circuit comprising an inductive element and a capacitive element in parallel, one of said elements being variable and the other ixed; means for amplifying and transmitting waves of any selected frequency in said range; means for displacing the 'frequency of the waves a given percentage ofthe 'selected frequency, this means comprising another reactive element of the same character as the fixed element and means for connecting thisiother reactive element into the tank circuit andldisconnecting ittherefrom; and a super-heterodyne receiving system having an intermediate frequency amplier tunable over a band corresponding to the difference between the initial and displaced frequencies of said waves throughout said range, a mixer delivering its output to the intermediate frequency amplifier, and a connection for supplyingthedisplaced waves from the si;4

K Number@ generatingmeans to the mixer, the` displaced wavesV servingasY the local heterodyning waves for saidreceiving system.

- 10.` Radio apparatus of the character described;-

including: wave generating means variable over Q9. 2,262,149-Y a. predetermined frequency range, this means including a"frequency"controlling tank circuit comprising an inductive' element and a capacitive element in parallel, one of said elements being variable and the other fixed; means for amplifying and transmitting Waves of any selected frequency in said range; means for displacing the frequency of the waves a given percentage of thegselected frequency, this means comprising another reactive element of the same character as the fixed element and means for connecting this other reactive lelement into the tank circuit andldisconnecting it therefrom; a super-heterodyne, receiving system having an intermediate frequency amplier tunable over a band correspondingto the difference between the initial and displaced frequencies of said Waves throughout saidrangeand a mixer delivering its output to tl'ie intermediate frequency amplifier; and selectively operable means for connecting the wave generatingmeans to the amplifying means in one opel'afiiieipositipn and for actuating the displacing means` andjconnecting the wave generating means to the mixer. 4of. the receiving system in another operative position, whereby the displaced 2Q Wavesuserve vas lhe local heterodyning waves for The vfollowing referencesare of record in the le of3 this patent:

' STATES PATENTS Name` .N

` Date 1,976,574: Y lalkenthalv Oct. 9, 1934 v2;113',419 YYoung Apr. 5, 1938 2,161605 Car1son July 25, 1939 Slonczewski Nov. 11, 1941 Certificate of Correction Patent N o. 2,447,490. August 24, 1948.

ARTHUR A. COLLINS It is hereby certied that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 7, for June 26, 1946 read June 25, 1.946; column 10, line 56 o l n claim 8, stmke out the Word var1ous;

y:and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 7th day of December, A. D. 1948.

THOMAS F. MURPHY,

Assistant 'ommzasz'oner of Patente.

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