US1561273A - Radio system - Google Patents

Description

Nov. 10,1925. 1,561,273

, H. W. NICHOLS RADIO SYSTEM Filed Nov. 24. 1924 Patented Nov. 10, 1925.

HAROLD W. NICHOLS, OF MAILEWOOD, NEWJERSEY, ASSIGNORTO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OE NEWYOBKg N.' Y., AiCOBPORATION OF NEW YORK.

RADIO SYSTEM;

Application led. November 24, 1924.1 Serial` No. 751,728.

l all who/1L z'z may concern.

Be itlmown that I, Hnnonn YV. Nici-rois, a citizen-of the United States of America, residing at Maplewood, in the countyA of 5 Essex-and State of New Jersey, have invented certain new and useful' Improvements in Radio Systems, of which the` followinO is ay full.l clear concise and eXact` description.

'Ihisinvention relates to radio systems andmore particularly to high power apparatus foritransmittingspeech over great distances.

In one type of radio telephone systems heretofore proposed, which incliidedamplitying devices supplied with rectified alternating current, it' has-been the practice to employ some forni of filtering devicel for supA ressing` the ripple component present in therectified current` supplied to the amplitiers. This was done in order to eliminate theV distorting effect due to the ripples, whereby the speech currents produced at the receiving station, except for extraneous interference, are substantially faithfulreplicaf of Vthe transmitted speech.

In relatively lowi power arrangements, involving'voltages offthe order ofa few thousand'volts` in which energy of upwards of one kilowatt is suppliedto the antenna, the cost ofthe filters and the power dissipated in them is small, and hence their use does not materially affect the cost of installation and maintenance, nor the efficiency of the system.

In high power systems, however, where energy is supplied to the'rectifying devices at several'thousand volts andenergyy ofthe amount of one hundred kilowatts or more is supplied to the transmission circuit, the initialcost of the filters would bier-great and the power dissipated in them would Lbe large. As a matter of fact in` such a system, the .filters would represent a relatively large percentage ofthe cost of installation and maintenance of the transmitting station and would introduce large power losses.

Ina second system which has been previously proposed, the speech currents are impressed.l upon the input circuit ofthe rectifying devices supplying energy to the amplifiers, and the-resulting speech modulated :rectifiedtcurrent is supplied'to the-plate circomponentwvhich appearsin the output cir-` cuit-ofthe oscillator as a-tone. Upon detection at the-receiving station the ripples mask the reproduced speech.

The presentV invention provides a systemy including alower power apparatus for producing a speech modulated carrier wave, the modulation products of which do not contain alcomponent of carrier frequency; impressing the resultantI components upon the input circuit of high power amplifying devices supplied with space current having.

af relatively large ripple component, and transmitting the resultant carrierI wave modulatedby bothl speech and the ripple component. Inthis arrangement, the rip,- ple component is superimposed upon the speech modulated side-band componentY and does not produce'a tone effect inthe wave supplied to the transmission .circuit. At the receiving station the quality of the-speech produced is somewhatimpaired, but the intelligibility of themessage is practically unaffected. Again, since the ripple component isonly` transmitted during the time when speech'modulatedwaves are radiated there isa materialsaving in the energy supplied tothe antenna ascomparedwith previously known systems.

An'ob'ject ofthis invention is to improve the efficiency of highpower apparatus for transmitting speech 'modulated carrierwaves without affecting the intelligibility of the message reproduced at the receivingjstation.

For a complete understanding of the invention, reference should be made to the following specification read in conjunctionwiththe attached drawing in which Fig. l

illustrates a radio transmitter embodying the invention, andzFig; 2 shows an alternative method of coupling the lower power.

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stance is shown as including a microphone 2 and battery 8 and may, therefore, be a telephone line, to a modulating apparatus 4 which is supplied with a wave of carrier frequency by a source 5.

The modulating apparatus may be of any well lmown type, but is preferably similar to that disclosed in U. S. Patent 1,343,307, June 15, 1920 to J. R. Carson. In accorciance with the disclosure in this patent, the speech currents from circuit 1 and the carrier wave from source 5 are combined to produce a modulated wave in which the component of carrier frequency is suppressed. Modulation products, therefore, consist solely of the side band components.

The side band components supplied by the modulator 4 are impressed upon the filter which is of the general type described in U. S. Patents 1,227,113 and 1,227,114, May 22, 1917 to G. A. Campbell and is designed to pass Without appreciable `attenuation one side band of the modulated wave, the other side band being thereby sup-A pressed.

The side band selected by the filter is ampliiied by the device A which may include as many stages of amplification as may be desirable. The amplified wave is transmitted through the coupling circuit C and impressed upon the input electrodes of the power amplifier Ap consisting of a plurality of parallel connected three-electrode space discharge devices 7. lVhile but three discharge devices are illustrated, it is to be understood that the power amplifier may consist of any number of parallel connect-ed devices of this type.

The coupling circuit C comprises Y a capacity 8 of low impedance for the high frequency wave shunted by resistance 9, in series with a loop circuit including an inductance 10, a branched circuit having an inductance 11 in one branch and a resistance 12 in the other branch, and a condenser 18. The elements 10, 11-12 and 13 are connected in series, to constitute a loop circuit tuned to the frequency of the high frequency wave. The potential drop across the branch circuit 11-12 is impressed upon the input electrodes of the power amplifier.

Heating current for the cathodes of devices 7 is supplied by the source 15 through a transformer 16.

Space current is supplied to the discharge devices 7 by an alternating current source, herein represented by the secondary winding of a six-phase transformer S, through rectiiiers 14 which are illustrated as twoelectrode space dischargedevices. An alternating current source 17 supplies heating current to the cathode of each of the rectiers 14 through a transformer 18.

rllhe siX-phase windings of the transformer are arranged in two groups hav-- ing their neutral points connected together by an inter-phase reactor 19. An intermediate point of the reactor is connected to the anodes of the devices 7. lilith this arrangement, and using a 60 cycle source, for example, the rectified current supplied to the anodes of the power amplifier will contain a principal ripple component of the order of 360 cycles which, therefore, lies in that portion of the speech range within which the larger portion of the energy of speech is concentrated. Ripple components which are multiples of the principal ripple component will ordinarily be too small to be talren into account but they will produce results of the same nature as the principal ripple component and hence may be considered to act in the same manner.

rfhe space current path of the devices 7 may be traced from ground at 20 to the anodes of the rectiliers 14, across the discharge paths within them to their cathodes, the different phase windings of the transformer S, reactor 19, anodes of the devices 7 across the spaces within them to their cathodes and ground at 21.

The alternating current output circuit of the power amplilier Ap extends from the anodes of devices 7 through the condenser 22, the circuit comprising the parallel connected condenser 3 and coil 24, tuned to the high frequency wave, cathodes of devices 7 and across the discharge paths within them to their anodes. The coil 24 is inductively associated with the coil included in the antenna circuit.

Fig. 2 illustrates an alternative arrange ment for coupling the amplified A to the power amplifier Ap. This coupling unit may be substituted for that shown between the section lines a-a and iof Fig. 1. The primary winding of the transformer 26 is included in the alternating current output circuit of the amplifier A. The secondary winding'of this transformer is connected in series with condenser 28 and resistance 29. The secondary winding of transformer 26 and condenser 28 cooperate to constitute a circuit tuned to the frequency of the modulated wave supplied by the ampli.- tier A.

The drop of potential across resistance 29 is impressed upon the input electrodes of thi,` amplifier Ap.

This method of impressing the high trequency wave upon the power amplicr serves to reduce the tendency to produce oscillations of undesired frequencies in thc ampliiier circuits. This is effected by using a resistance 29 of a value such that the amplitude of the wave impressed upon the input electrodes of the amplifier Ap is so limited that the coupling` between its input and outputl circuits is insufficient to maintain the production of undesired oscillations.

A systemsimilar to thatidescribed above, used for. transatlantic telephone transmission, consisted of twenty parallel connected:

devices eachiadaptedto supply upwards of ten kilowattsl to theantenna. Current'produced by rectifying 60 cycle alternatingcur-v rent. was supplied at from 10,000to 12,000 voltseto the parallel connected'devices. The discharge devices are. operated'with a comparatively. large negative; grid polarization,

ponent was of the order of 360 cycles and constituted approximately 15% vofz'the power suppliedto the devicesz';.intelligible speech of relatively goed quality was reproduced at the receiving station. rl-his may be explained by the fact that the high frequency modulated wave wasy impressed upon the input electrodes offthe devices 7 while the ripple component is-applied to the output circuit of these devices and;consequently the voltage variationsdue to the ripple do not appear as a tone in the output circuit of the amplifier. The effect of the ripples is to cause the modulated `band to shift back and forth in the frequency spectrum` by an amount corresponding to the ripple component, whereby the width of the band transmitted:A is extended. ln other words, the ripple appears in the received signal, not as waves of the ripple frequency but as waves of the speech frequency plus and minus the ripple frequency.

At the receiving station, the incoming widened frequency band was selected by means tuned to pass it without appreciable attenuation and was combined with locally generated oscillations of carrier frequency.

There was, therefore supplied to the tele-v phone receiver a composite current consisting of variations representing speech having the ripple component superposed thereon. Thus if the signal wave be represented in frequency as s and the ripple frequency by r there will appear in the received signal components of frequency s-r and s-l-rlas well as s. If the components of frequencies .9*1" and s-l-r are not too large the effect upon the intelligibility and naturalness of the speech is quite immaterial..

The alternating current may be supplied to power amplifiers from a source of four or more phases, whereby the principal ripple component will lie within the range where speech energy is largely concentrated, and the intelligibility of the conversation will not be materially affected. However, the application of the invention is not limited to the use of any particular number of phases.

Fromthe preceding description, it will be seen that the present invention provides a system in which 4expensive ripple filters are dispensed with. and hence their initiallcost. andthe power losses consequent upon their use are eliminated. Again, since the ripple component is produced onlyduringpthe time speech is transmitted, the. power losses cntailed by the presence of the ripples is considerably reduced. Also the intelligibilityy of the speech reproduced at the distant station is substantiallyv unaffected.

. As compared with previously known systems, the arrangement described in this application embodies features of considerable importance, especially when applied to high power systems, since their use permits the initial cost of installation and maintenance, and'power losses to be considerably reduced while permitting intelligible speech to be V transmitted over long distances.

1v'vlhile the invention has been described with reference to a specific embodiment and specific details have been given inorder to clearly andcompletely discloseits nature, it

is to be understood that this invention is not limited to the particular use or details hereinset forth but only by the scope of` the attached claims.

That is claimed is:

l. A radio transmitting system, comprising means for producing a carrier wave modulated in accordance with speeclrcur.- rents while suppressing the component of carrier frequency, and means for raising said wave to high power comprising an amplifier supplied with energy having an appreciable ripple component. p

2. A radio transmitting system, comprising means for producing a single side band speech modulated wave, an amplifier for raising said wave to high power, and means for supplying to said amplifier energy having an appreciable ripple component.

3. A radio transmitting system, comprising means for producing a single side band speech modulated carrier wave, a space discharge amplifier' for raising said wave to high power, and means for supplying to said space discharge amplifier energy having an f appreciable ripple component.

t. A radio transmitting system, comprising means for producing a single side band speech modulated carrier wave, means for raising said wave to high power comprising a power system including space discharge devices, and means for supplying to said devices energy having an appreciable ripple component.

5. A transmitting system havingl means for producing al single side band of a signal modulated wave, a space discharge amplifier for amplifying said wave, a source of alternating current of a plurality of phases, and rectifying means for said alternating current, whereby said amplilier is supplied with direct current.

6. A transmitting system having inea-ns for producing a single side band of a signal 5 modulated wave, a space discharge amplifier for amplifying said wave, a source of alternating current of a plurality of phases, and rectifying means for said alternating current, whereby said amplifier is supplied l0 with direct current having ripples of material value superimposed thereon.

'i'. A radio transmitting system, comprising means for producing a single side band speech modulatedL carrier wave, means for raising said wave to high power comprising a power system including space discharge devices, and means for supplying space cui'- rent to said devices comprising an alternating current source of at least four phases and a rectifier.

8. A modulating systeii'i comprising means for producing` a single side bandpecchmodulated carrier wave, a high power amplifier therefor comprising space discharge devices supplied with space current by a plural phase alternating current source and a rectifier in which the ripple component resulting from rectification is supplied to the space paths of said devices.

9. A radio transmitting system, comprising means for producing a single side-bandspeecli-modulated carrier wave, aliigh power amplifier therefor including space discharge devices, means for impressing the modulated wave upon the input circuit of said amplilier, and means for supplying space current to said devices from a plural phase alternating current source and a rectiiier, whereby the ripple component resulting from rectification is superposed upon said modulated carrier wave.

l0. A modulating system having means for producing a single side band of a signal modulated wave, a space discharge amplitier for amplifying said wave, al source of alternating current of a` plurality of phases, rectifying means for said alternating current, whereby said amplifier is supplied with direct current, and inea-ns for supplying alternating' current for heating the filaments of said devices.

ll. A modulating system comprising means for producing a single side-bandspeech-modulated carrier wave, a high power amplifier therefor comprising space discharge devices supplied with space current by a plural phase alternating current source and a. rectifier in which the ripple component resulting from rectification is supplied to the space paths of said devices, and means for supplying alternating current for heating the iilaments of said devices.

In witness whereof, I hereunto subscribe niy name this 21st day of November A. D., 1924.

HAROLD W. NICHOLS.

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