# Патент USA US2405765

код для вставкиPatented Aug. 13, 1946 , 2,405,765 UNITED STATESl PATENT OFFICE 2,405,765 RADIO REPEATER J. Ernest Smith, Brooklyn, N. Y., assìgnor to Ra dio Corporation of America, a corporation of Delaware Application February 12, 1942, Serial No. 430,527 30 Claims. (Cl. Z50-15) f Y 2 l The present invention relates to radio re peater or relay stations and,»more particularly, to such stations as are adapted to utilize ultra high frequency waves for relaying television or similar signals. In ordinary transmission parlance, a repeater is considered to be an amplifier having an out put signal frequency dependent upon the fre quency of the input signal. Amplification of fre quencies in the neighborhood of 500 megacycles for a band width sufficient for high ñdelity tele vision transmission is diñicult with many ampli ñer tubes -available at the present time. To over- ' are obtained in accordance with the principles of the present invention by providing a crystal con trolled oscillator and another oscillator, mixing the output of said oscillators or modulating the output of one of the oscillators, either in ampli tude or wavelength, by the other of the oscillators and separating the sum and difference fre quencies thus obtained. One of these frequencies is mixed with an incoming band of frequencies to obtain a signal at a comparatively low inter mediate frequency Which may be conveniently amplified without adversely affecting the width of the band of the frequencies. The amplified band of frequencies is then mixed with the other come this difficulty, the ultra high frequency sig nal is heterodyned to a lower frequency band, 15 of the sum and difference frequencies to convert the band to a position in the radio frequency amplified and heterodyned back to an ultra high spectrum near that of the incoming band of fre frequency band for retransmission. Further, the quencies and, also, thus dropping out the effect retransmitted band normally does not coincide of any frequency drift in the local oscillator. The with the received frequency band but is difier entially spaced therefrom to avoid feedback be 20 converted band of frequencies is then transmit tween the transmitting and receiving antennas and their associated circuits. While the present heterodyning practice permits satisfactory am plification at ultra high frequencies, it intro duces, at the same time, the necessity for fre quency monitoring of the retransmitted signal since its frequency is a function of the heterodyn ing oscillator frequency. Moreover, if the relay ted to the Succeeding amplifiers in the relay sys tem. ’ The present invention will be more fully un derstood by reference to the following detailed description which is accompanied by a drawing in which: Figure 1 illustrates the frequency distribution, in a portion of the radio frequency spectrum, of system incorporates antennas having band various frequencies used in an embodiment of Widths sufficient for the simultaneous transmis 30 the invention; While Figure 2 is a diagram in conventional block sion of a video channel and an adjacent sound or “cue” channel, it is possible for cross-talk to formation of an embodiment of the invention; result due to drift of the heterodyning frequencies Figure 3 is a curve illustrating the operation at one of the repeaters. of a portion of Figure 2; and An object of the present invention is to over 35 Figure 4 illustrates a modification of the em come the foregoing difficulties and disadvantages. bodiment of Figure 2, and a different order of A further object of the present invention is application of the operations of the invention. to improve the frequency stability of radio relay Reference will now be had to the drawing, Fig equipment. ure 1 shows the frequency spectrum arrangement Another object of the present vinvention is the 40 wherein the incoming frequency fs is heterodyned provision of a radio relay station which may be with a local frequency (fc-fk) giving the low in conveniently controlled and supervised from the termediate frequency band (fs-fc-l-fk) lwhich terminal stations of a relay system. may be amplified with-out difliculty. The ampli fied signal is then heterodyned with another A further object of the present invention is the provision of a relay system which will not require 45 local frequency (fc-l-fk), thus resulting in the fre frequency monitoring at each of the interme quency (J‘S-i-2fk) which is to be retransmitted. The frequencies fc and fk from which the sum diate repeater stations. and difference frequencies are derived are locally Still a further object of the present invention produced by oscillation generators, that for fre is the provision of a system of amplifying ultra high frequency radio waves wherein the output 50 quency fk being crystal controlled. It will be noted that the outgoing frequency (fs-l-Zfk) is signal from the amplifier means is determined independent of the oscillator frequency fc. substantially only by the frequency of the in The frequency ,fk may conveniently be of the coming waves. order of 10 megacycles and is, therefore, prefer The foregoing objects and others, which may appear from the following detailed description, 55 ably derived from a crystal oscillator. Its drift, 3 l therefore, compared to the outgoing carrier fre frequencies in the output of modulator I2. Dis quency of the order of 500 megacycles is neg criminator 22 may be a conventional frequency modulation receiver incorporating a back-to back discriminator and an amplitude detector. The discriminator 22 should have a characteris ligible. n ' In Figure 2 is shown an embodiment of the invention for performing the operations outlined above. Frequency fk is generated by crystal os cillator I0 and applied to balanced modulator I2 in a push-pull relationship. Another frequency fe generated by oscillator I4 vis applied to bal anced modulator I2 in push-push relationship.Y 10A This is a well known carrier suppression system - of modulation and therefore needs no further description. The output frequencies from balanced modu tic with respect to the frequencies (fc-fk) and (fc4-jk) as shown in Figure 3, wherein curves 24 and 26 illustrate the frequency-output voltage characteristics Vof the halves of the back-to-back discriminator. It Will ibe seen that as long as the frequency (fc-fk) and the frequency (fc4-fk) cut curves 24 and 26 at points equally distant from the cross over point the output potential is A’zeroL A shift in either direction will result in lator I2 consist substantially‘of two side" bands 15 ` ' _a positive or negative resultant output potential. This direct resultant output potential is arranged only, namely, (fc-fk) and (fc-Hr). The fre quency (fc-fk) is applied to converter I6 and» - to be applied as a variable bias to oscillator I4 there heterodyned with an incoming signal` is whereby the frequency fc is controlled in such arriving from a preceding station by way -of-re sense that the output frequencies of modulator ceiving antenna RA, giving an intermediate fre 20 I2 are shifted in the desired direction. quency (fs-fe-i-fk). This frequency may be am In vFigure 4 is shown a modification of the plified in a conventional amplifier I8 toV any embodiment of Figure 2 wherein the balanced desired extent. After` ainpliñcation the inter modulator arrangement I2 of Figure 2 is not used. mediate frequency signal is Vheterodyned with In this figure the incoming frequency is shown the component (fc-HJC) in converter 20 thus pro 25 as (fs-l-Zfk) , the output frequency of the embodi ducing the output frequency (fs-l-Zfr). The out ment of Figure 2. The discriminatory character put frequency is applied to transmitting antenna istics of ñlter networks 30 and 32 are relied upon TA for retransmission to succeeding relay sta to Aselect the first lower and upper side bands tions'. The antennas RA and TA Lare preferably (fc-fk) and (fc-Hr) resulting from a mixing of of the directive type with their zonesof maxi 30 frequencies fc‘ and fk, in modulator 24, while re jecting the frequency je and components of higher mum response directed away from each other and toward relay stations. „ ‘ " ‘ It should be understood »that the frequency components shown in Figures'l and 2 and spe order. Since rather severe selectivity isl required of Afilter networks Si? and 32 to discriminate against the frequency fc while passing frequencies cifically mentioned are those which are essential 35 (fc-fk) to the operation of the system. Other modula tion products would be present but selective cir cuits in the system may be provided to discrimi nate against them.> Therefore, in order to reduce and (gfe-l-fk) for straight mixing or amplitude modulation, the crystal oscillator out put fk may be arranged to frequency modulate in modulator 24 the frequency fe generated by oscillator I4. The modulation index may be ad the number of other modulation products a filter 40 justed to emphasize the ñrst of the side bands 3D is provided in the channel between converter with respect to the frequency fe and higher order 2i) and modulator I2 and a filter 32 is provided components. For example, if a modulation index between converter I5 and modulator I2. These of about 2.4 is used, the amplitude of frequency filters assure that only a single frequency as indi fc is reduced to zero and at the same time the cated is fed tofeach converter. Then the output 45 maximum fundamental or first order side band of converter I 6 may be arranged to pass only amplitudes are obtained. The channel carrying the desired difference frequency fs-fc-l-fk while frequencies (fc-I-fk) and (fe-fk) may include an discriminating, for example, against the sum fre amplitude hunting transducer device if desired. quency J‘s-l-fc-fk. Likewise, the output of con While I have used a modulation index of 2.4 in verter 2l) may be arranged to pass only the sum order to illustrate the selective property of this frequency fs-l-Zjk discriminating, for example, type of modulation, it is to be clearly understood against the difference frequency J‘S-Zfcv. In order to illustrate the stability of the outgoing signal that my invention is not limited to that value, (fel-21%), suppose a frequency drift of 5 kilo since under some circumstances` a modulation index of about 1.8 may be preferable. A modu cyclesis allowed crystal oscillator IQ. Theout lation index of this order gives aA maximum ratio going signal then has a maximum drift rof l0 kilocycles in 50 megacycles or .002 percentA which, for all practical purposes, is negligible. >Obvi of fundamental to carrier and fundamental to ` second order side band amplitudes. The ampli fied intermediate frequency is fs-fc-I-jk, the same ously, the method described above is equally» ap as in the previous example. plicable to an amplitude or to ¿a frequency modu dyned with the other side band frequency (fc-__fr) andthe Vupper beat frequency, which becomes fs, selected for retransmission. The outgoing frequencies of the Vrepeaters using alternate orders of application of the >side band frequencies lationA system. ‘ _ Y Y » The system asso far described insures ¿that Athe retransmitted frequency band will not-drift'. Y,lt It is then hetero does not, however, maintain the frequency band to be amplified, that is, the frequency (fs-fe-l-fe), 85 thus are alternately js and (fel-2jr) throughout the system. ` constant since this frequency is a function of jc. Due to the difficulty of obtaining wide enough While I have particularly described and illus pass bands at low frequencies to vobviate the tratedseveral modiiicationsof the present in effect of this drift, according to a further aspect vention, Vit should be distinctly understood that of the present invention, automatic frequency 70 my invention is not limited thereto but’may be control of oscillator I4 may be provided. Side varied within the scope o_f the appended claims. band clipping in amplifier I8 is thus prevented l. In a’ radio relay system, a stationincluding since the position 0f band (Ís-.fc-I-J‘k) is main tained constant. This may be accomplished by receiving and transmitting antennae, a low-fre supplying discriminator unit 22, Aresponsive to the 75 quency oscillator of high frequency stability, an 2,405,765' . 6, other oscillator, modulator means for so com bining the output of said oscillators that sum and difference frequencies are generated, a first con verter means for mixing one of said frequencies with incoming high frequency energy from said receiving antenna for obtaining a low interme-` diate frequency, means for amplifying said in termediate frequency, a second converter means for mixing the other of said sum and difference put energy at a high frequency adjacent the fre frequencies With said amplified intermediate fre lator that the Wavelength of Ythe output is modu- ` lated thereby, a first converter means for mix quency to obtain output energy at a high fre quency of said incoming energy and means for applying said output energy to said transmitting antenna for radiation. 6. In a radio system, a station including receiv ing and transmitting antennas, a 10W frequency oscillator of high frequency stability, another oscillator, means for so applying the output of said low frequency oscillator to said other oscil quency adjacent the frequency of said incoming energy and means for applying said output en ergy to said transmitting antenna for radiation. ing one output frequency with incoming high fre other oscillator, modulator means for so combin quency oscillator that sum and difference fre quencies are generated, a ñrst converter means quency energy from said receiving antenna for obtaining a low intermediate frequency, means for amplifying said intermediate frequency, a sec 2. In a radio system, a source of high frequency ond converter means for mixing another of said energy, a low frequency oscillator of high fre output frequencies With said amplified interme quency stability, another oscillator, modulator diate frequency to obtain output energy at a high means for so combining the output of said oscil- > frequency adjacent the frequency of said incom lators that sum and difference frequencies are generated, a ñrst converter means for mixing one 20 ing energy and means for applying said output energy to said transmitting antenna for radiation. of said sum and difference frequencies with said '7. In a radio relay system, a station including first mentioned high frequency energy for obtain receiving and transmitting antennae, a low fre ing a low intermediate frequency, means for quency oscillator of high frequency stability, an amplifying said intermediate frequency, a second other oscillator, modulator means fo-r so combin converter means for mixing the other of said sum ing the output of said oscillators that sum and and difference frequencies with said amplified difference frequencies are generated, a first con intermediate frequency to obtain output energy verter means for mixing one of said frequencies at a high frequency adjacent the frequency of With incoming high frequency energy from said said source. 3. Ina radio relay system, a station including 80 receiving antenna for obtaining a 10W interme diate frequency, means for amplifying said inter receiving and transmitting antennae, a loW fre mediate frequency, a second Converter means for quency oscillator of high frequency stability, an mixing the other of said sum and difference fre other oscillator, modulator means for so com quencies With said ampliñed intermediate fre bining the output of said oscillators that sum and difference frequencies are generated, a first con 35 quency to obtain output energy at a high fre quency adjacent the frequency of Said incoming verter means for mixing said difference fre energy and means for applying said output energy quency with incoming high frequency energy to said transmitting antenna for radiation, means from said receiving antenna for obtaining a 10W equally responsive in opposite senses to said sumintermediate frequency, means for amplifying said intermediate frequency, a second converter 40 and difference frequencies for obtaining a control potential and means for applying said potential to means for mixing said sum frequency with said control the frequency of said other oscillator. amplified intermediate frequency to obtain out 18. In a radio relay system, a station including put energy at a high frequency adjacent the fre receiving and transmitting antennae, a low fre quency of said incoming energy and means for quency oscillator of high frequency stability, an applying said output energy to said transmitting other oscillator, means for so modulating the fre antenna for radiation. s quency of said other oscillator by said low fre 4. In a radio system, input and output circuits quency oscillator that sum and difference fre for high frequency energy, a low frequency oscil quencies are generated, a first converter means lator of high frequency stability, another oscil for mixing one of said frequencies With incoming lator, modulator means for so combining the out high frequency energy from said receiving an put of said oscillators that sum and difference tenna for obtaining a low intermediate frequency, frequencies are generated, a first converter means means for amplifying said intermediate fre for mixing said difference frequencies with high quency, a second converter means for mixing the frequency energy from said input circuit for ob taining a low intermediate frequency, means for 55 other of said sum and difference frequencies with said amplified intermediate frequency t-o obtain amplifying said intermediate frequency, a second output energy at a high frequency adjacent the converter means for mixing said sum frequency frequency of said incoming energy and means for with said amplified intermediate frequency to applying said output energy to said transmitting obtain output energy at a high frequency adjacent the frequency of the energy at said input circuit 60 antenna for radiation. 9. In a radi-o relay system, a station including and means for applying said output energy to said receiving and transmitting antennae, a low fre output circuit. quency oscillator of high frequency stability, an 5. In a radio relay system, a station including otherV oscillator, means for so modulating the fre. receiving and transmitting antennae, a low fre quency oscillator of high frequency stability, an 65 quency of said other oscillator by said low fre ing the output of said oscillators that side band for mixing one of said frequencies with incoming frequencies are generated, a first Converter means high frequency energy from said receiving an for mixing one of said side band frequencies with incoming high frequency energy from said receiv 70 tenna for obtaining a low intermediate frequency, means for amplifying said intermediate fre ing antenna for obtaining a 10W intermediate fre quency, a second converter means for mixing the quency, means for amplifying said intermediate other of said sum and difference frequencies With frequecy, a second converter means for mixing said amplified intermediate frequency to obtain another of said side band frequencies With said amplified intermediate frequency to obtain out 75 output energy at a high frequency adjacent the 2,405,765 1 7 incoming high frequency energy from said re frequency of said incoming energy and means for ' applying said output energy to »said transmitting antenna, for radiation, means Yequally responsive ceiving antenna for obtaining a low intermediate frequency, meansfor amplifying said intermedi in opposite senses to said sum and difference fre- l ate frequency, a second converter means for mix quencies for obtaining a control potential and means for applying said potential to control the ing said difference frequency with said amplified intermediate frequency to obtain output energy at a high frequency adjacent the frequency of said incoming energy and means for applying 10. In a radio relay system, a station including said output energy to said transmitting antenna receiving and transmitting antennae, a. low fre quency oscillator of high frequency stability; ‘an 10 for radiation, means equally responsive in oppo frequency of said other oscillator. ' _ site senses to said sum and difference frequencies for obtaining a control potential and means for otherV oscillator, modulator means for so combin ing the output of said oscillators that sum and difference frequencies are generated, a first >con- applying said potential to control the frequency of said other oscillator. verter means for mixing said difference frequency 14. In a radio relay system, a station including with incoming high frequency energy from said 15 receiving antenna for obtaining a low interme receiving and transmitting antennas, a'low fre diate frequency, means for amplifying said inter quency oscillator of high frequency stability, an other oscillator, means for modulating the Wave length of the output of said other oscillatorby mediate frequency, a second converter means for mixing said sum frequency with said amplified intermediate frequency to obtain output energy 20 said low frequency oscillator, a first converter at a high frequency adjacent the frequency of means for mixing the first upper sideband fre said incoming energy and means for applying said quencies of the output of said modulator means output energy to said transmitting antenna for With incoming high frequency energy from said radiation, means equally responsive in opposite receivingr antenna for obtaining a low intermedi senses to said sum and difference frequenciesmfor Aa5 ate frequency, means for amplifying said inter obtaining a control potential and means for ap mediate'frequency, a second converter means for plying said potential to control the frequency of mixing the first lower sideband frequency of the said other oscillator. output of `said modulator means with said ampli 11. In a radio relay system, a station including fied intermediate frequency to obtain output en-Á receiving and transmitting antennas. Ya low fre 30 ergy'at a >high frequency adjacent the frequency quency oscillator of high frequency stability, an of said incoming energy and means for applying other oscillator, means for frequencyA modulating said output energy to said transmitting antenna said other oscillator by said low frequency oscil for radiation. ' « lator, thelmodulation index being such that the 15. In aV radio relay system, a station including receiving and transmitting antennas, a low fre sum and difference frequencies predominate in the output. a first converter means for mixing said difference frequency with incoming high fre quency energy from said receiving antenna for obtaining a low intermediate frequency, means quency oscillator of high frequency stability, an other oscillator, means for modulating the Wave length of the output of said other oscillator by said low frequency oscillator, filter means for sep for amplifyingsaid intermediate frequency, a sec 40 arating the sum frequency and the difference fre ond converter meansìfor mixing said sum fre quency from the output of said modulator, a first quency with said amplified Y intermediate fre converter means for mixing one of said frequen quency to obtain output energy at a high fre cies with incoming high frequency energy from quency adjacent the frequency of said incoming said receiving antenna for obtaining a low inter energy and means for applying said output en mediate frequency, means for amplifying said in ergy to said transmitting antenna for radiation. termediate frequency, a second converter means 12. In a radio relay system, astation including for mixing the other of said sum and differenceV receiving and transmitting antennas, a low fre frequencies `With said amplified intermediate fre quency oscillator of high frequency stability, an quency to obtain output energy at a high fre other oscillator. means for frequency modulating _ 50 quency adjacent the frequency of said incoming said other oscillator by said low frequency oscil energy and means for applying said output en ergyV to said transmitting antenna for radiation. lator, the modulation index being such that the sum and difference frequencies predominate in 16. A radio relay system including a plurality Y the output, a ñrst converter means for mixing said difference frequency with incoming high fre of stations as set forth in claim l, alternate ones 65 qency energy from said receiving antenna for ob taining a low intermediate frequency, means for amplifying-said intermediate frequency, a second converter means for mixing said sum frequency with said amplified intermediate frequency to ob tain- output energy at a high frequency adjacent the frequency of said incoming energy and means for applying saidv output energy to said transmit ting antenna for radiation, means equallyY re sponsive in opposite senses to said sum and dif ference frequencies for obtaining a control poten tial and means for applying said potential to con trol the frequency of said other oscillator. 13. In a radioY relay system, a station including receiving and transmitting antennas, a low fre quency oscillator of high frequency stability, an other oscillator, modulator means for so combin ing the output of said oscillators that sum and difference frequencies are generated, a first con verter means for mixing said sum frequency with of said stations utilizing said difference frequency in said first converter and said sum frequency in said second converter, the other stations of said system having the order of application of said (if) sum and difference frequencies reversed. 17. A radio relay system including a plurality of stations as set forth in claim 8, alternate ones of said stations utilizing said difference frequency in said first converter and said sum frequencyl in said second converter, the other stations of said system having the order of application of said sum and difference frequencies reversed. ' 18. A radio relay system including a plurality of stations as set forth in claim 9, alternate onesV of said stations utilizing said difference frequency in said first converter and said sum frequency in said second converter, the other stations of said system having the order of application of said sum and difference frequencies reversed. 19. In a radio system, a source of high fre- ,f _quency energy, a low frequency oscillator~ of _high f. 2,405,765 10 frequency stability, another oscillator, modulator cludes generating a relatively low frequency local means for so combining the output of said oscilla wave, generating a local carrier wave, frequency tors that sum and difference frequencies are gen modulating the carrier Wave with the local Wave erated, a converter means for mixing one of said to such a degree that the carrier has substantial sum and difference frequencies With said first ly zero Value in the waves resulting from the mod mentioned high frequency energy for obtaining a ulation process in order to facilitate filtering of low intermediate frequency and means for ob side bands on either side of the carrier, filtering taining a control potential from said low interme a side band frequency resulting from the modula diate frequency and means for utilizing said con tion process, heterodyning the `wave to be con trol potential to control the frequency of said 10 verted with the filtered side band, selecting a beat wave resulting from the heterodyning process, other oscillator. 20. In a radio system, a low frequency oscilla heterodyning the beat to a high frequency, and tor of high frequency stability, another oscillator, utilizing the resultant high frequency Wave. means for so applying the output of said low fre 26. The method of Wave conversion which in quency oscillator to said other oscillator that the 15 cludes generating a local Wave, generating a local Wavelength of the outputU is modulated thereby, carrier Wave, frequency modulating the carrier converter means for mixing one output frequency with the local Wave to such a degree that the car from said modulating means with other high fre rier is reduced substantially to zero in the Waves resulting from the modulation process in order to quency energy to obtain a low intermediate fre quency and utilization means for said low inter 20 facilitate filtering of side bands apart from the mediate frequency. carrier, filtering a side band frequency Wave ly ing to one side of the carrier frequency, hetero 21. In a radio system, a station including a re dyning a Wave to be converted with the filtered ceiving antenna, a low frequency oscillator of side band frequency wave, amplifying a beat Wave high frequency stability, another oscillator, means for so modulating the frequency of said 25 resulting from the heterodyning process, and heterodyning the amplified beat with another side other oscillator of said low frequency oscillator band frequency filtered from the modulated that sum and difference frequencies are gener waves. ated. converter means for mixingr one of said fre quencies’ with incomingr high frequency energy 27. The method of converting modulated waves from said receiving antenna for obtaining a low 30 of a given mean frequency to modulated waves of another mean frequency which includes gener intermediate frequency, utilization means for said ating a local relatively high frequency carrier intermediate frequency and means equally re wave, generating a relatively low frequency Wave, sponsive in opposite senses to said sum and dif producing sum and difference frequencies with ference frequencies for obtaining a control poten tial and means for applying said potential to con 35 the locally generated Waves, successively hetero clyning waves derived from the modulated Waves trol the frequency of said other oscillator. of given mean frequency with the said sum and 22. In a radio system, a station including a re difference waves, and utilizing a beat Wave de ceiving antenna, a low frequency oscillator of rived from the last heterodyning process. high frequency stability, another oscillator, means for modulating the Wavelength of the output of 40 28. The method of converting modulated Waves of given mean frequency to Waves of another said other oscillator by said low frequency oscilla mean frequency Which includes generating a local tor, converter means for mixing the ñrst upper carrier wave, generating a local constant fre sideband frequencies of the output of said modu quency modulating Wave, carrier suppression lator means with incoming high frequency ener gy from said reeceiving antenna for obtaining a 45 modulating the carrier with the 10W frequency 4 modulatingr Wave, ñltering the side bands result low intermediate frequency, and means for am plifying said intermediate frequency. 23. 'I'he method of Wave conversion Which in ing from the modulation, heterodyning the mod ulated Waves of mean frequency with one of the side bands to produce a relatively low, readily am cludes generating a relatively 10W frequency local wave. generating a local carrier wave, frequency 50 plifiable modulated intermediate frequency wave, amplifying the relatively 10W, readily ampliiiable modulating the'carrier wave With the local Wave intermediate frequency wave, and heterodyning to such a degree that the carrier has substantially the amplified intermediate frequency wave zero value in the Waves resulting from the modu lation process in order to facilitate filtering of against the other filtered side band to produce side bands on either side of the carrier, filtering a 55 the modulated waves of the desired mean fre quency. side band frequency resulting from the modula tion process. heterodyning a wave to be converted 29. The method as defined in the claim 28 Which includes the step of utilizing a portion of with the filtered side band, and utilizing a beat wave resulting from the heterodyning process. the carrier suppression modulated waves to con 24. The method of wave conversion which in 60 trol the frequency of one of the locally generated Waves. cludes generating a relatively 10W frequency local Wave, generating another local Wave. frequency 30. The method of wave conversion which in modulating said other local Wave With the first cludes locally generating a pair of Waves of dif mentioned local Wave to such a degree that the ferent frequency, producing sum and difference said other local wave has substantially zero value 65 frequency Waves from the locally generated in the Waves resulting from the modulation proc Waves, utilizing a portion of the sum and differ ess in order to facilitate selection of one of the ence Waves to frequency control the frequency remaining modulation products, selecting a side of one of the locally generated Waves, and suc band frequency resulting from the modulation cessively heterodyning waves derived from waves process, heterodyning a wave to be converted of one mean frequency with said sum and differ ence frequency Waves to produce a Wave of dif with the selected side band, and utilizing a beat Wave resulting from the heterodyning process. 25. The method of wave conversion which in ferent mean frequency. J. ERNEST SMITH.

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