US2110444A - Transmission of messages or pictures over long distance lines - Google Patents

Description

March 8, 1938. J. .1.V LAUB ET AL TRANSMISSION OF MESSAGES OR PICTURES OVER LONG DISTANCE LINES Filed July 3l, 1933 Amr:

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Y WWTP Patented Mar. 8, 1938 UNITED STATES TRANSMISSION OF MESSAGES OR PIC- TUBES OVER LONG DISTANCE LINES Jacobo J. Laub, Breslau, and Friedrich Kirschsten, Berlin-Tempelhof, Germany, assignors to Radio Patents Corporation, New York, N. Y.

Application July 31, 1933, SerlalNo. 682,922 In Germany July 30, 1932 35 Claims.

(Granted under the provisions of sec. 14, act of March 2, 1927; 357 0. G.

It ls well known to use high-frequency carrier waves upon which low-frequencyv or other currents representative of intelligence to be transmitted are modulated directly or by the use of in- 5 termediate frequencies, for so-called wired wireless transmission from point topoint along telephone or telegraph wire lines. 'I'he original audio or other current modulated upon the carrier at one point is then demodulated from the carrier wave by means of a detecting receiver at another point. By using a number of carrier waves having sufliciently different frequencies, a corresponding number of telephone conversations or other communications can be carried on and transmitted,

l" respectively, simultaneously over one line. i

'Ihe carrier waves generally are greatly weak- -ened (damped) while proceeding along the line. It has hitherto been believed that such weakening or attenuation of the carriers increases with increasing frequencies. For this reason carrier wave frequencies below 40 kilocycles per second or. what means the same, of more than A'7,500 meters in length, have only been used in practice. Higher carrier frequencies, i. e. shorter carrier waves, have not been 'used because their damping, or attenuation, by aperiodical long-distance telephone circuits and lines was considered to be so excessive that no considerable distances could be bridged over by them. It was also believed that the use of such short waves in wired wireless transmission is accompanied by an undesired lateral radiation of energy in the 'form of electromagnetic Waves proceeding transversely from the lines, thereby destroying secrecy of the signals andnessages going to be transmitted.

The limitation of the carrier frequency range to below 40 kilocycles had the eect that only a small number e. g. of conversations could be carried on simultaneously over one line (about 4 at the utmost) from one point to another one, and that the different conversations could be separated at the receiving points of the lines only with great difficulty and by means of extremely large and accordingly expensive lter chains. In addition hereto, the disturbance (or noise) level within that frequency range has been proven to bekv'eiygreat in practice, especially on open-air lines so'that hitherto one expected only a comparatively low amplification of the incoming carrier wave current.

Extensive investigations of the inventors showed the surprising result that carrier waves within the range of about 85 to 10,000, and more, kilocycles per second can be used and are of particular and extreme advantage in comparison with far lower carrier wave frequencies hitherto used. This applies not only to lines comprising aperiodical open-air lines, but also to cable lines (trunk lines) comprising aperiodical non-concentrical conductors.

'Ihe reasons for that phenomenon as investigated and established by the inventors are, among others, the following:

It was first found that, contrary to common expectation, no essential losses of energyvor power caused by electro-magnetic radiation from the lines take place if carrier frequencies from about 85 to about 10,000, and more, kilocycles are used. For instance, at a distance of 100 meters laterally from an open-wire line along which a modulated carrier wave of 40 meters length (7500 kilocycles) and of ar few watts energy has been transmitted, no messages modulated upon that carrier could be picked up even with most sensitiver receivers. Consequently, by the use of carrier wave frequencies within the range of the invention practical secrecy o f all intelligence transmitted thereon is secured. Very surprisingly it was also found that the damping, or attenuation, of carrier waves transmitted over a given distance does not increase with their frequency in the high ranges, concerned by this invention, in the way as was hitherto generally believed. The inventors seek an explanation of this fact therein that the damping of those waves is merely due to the so-called copper losses inthe wires and not substantially to radiation losses, the latter .being found much less than expected.

Equally surprising it was found that the disturbance or noise level of the line decreases rapidly with increasing frequency of the carrier wave so that the degree of amplification of thereceiving circuit or circuits can be easily increased, and this to a greater extent than in the casel of carrier waves of the range hitherto used.

While a damping, or attenuation, equivalent to 4 Neper at the carrier frequency heretofore used was so far assumed to be the highest admissible one between two points of a line, according Vto the invention and obviously due to its surprising findings outlined above, dampings or attenuations e. g. up to 10 to 12 Neper on open-wire lines at the frequency used, and in case of cables and trunks even up to Neper and more, could be safely overcome by using the high-frequency v range suggested by the invention.

In other words, by means of the invention far greater distances between a transmitting and a receiving point can be bridged over than heretofore.-

This may be explained by reference to the drawing which shows, in a diagrammatical way only, in Fig. 1 as ordinates the valuesof the losses of energy (level of damping or attenuation),-if transmitted over aperiodical open-air lines, per unit of length of the line and the course of the disturbance (noise) level, both on the same scale and dependent upon the carrier wave Ileqllencies whlchlare shown as absclssae. As it rio ample it may be meniloned thatfby meansof` waves within the frequency range accordingto the invention. and with a transmitter output energyofafewwattsdistancesof800to380v miles causing an attenuation of e. g. to` -12 carried on and transmitted simultaneously over ofothermaterialsuchasironorsteelcanbe Neper at the carrier frequency, can still be served over substantially aperiodicalopen-air lines comyrisingwiresofadiameteroH millimeter-with-` out applying anyintermediateamplification, and if cablesk with substantially aperiodicai non-concentrical conductors are used. distances up to miles and more. causing a still higher attenuation tban 10 to 12 Neper at the carrier frequency. can be safely 'bridged over in the same The use of carrier waves having a high irequency range in accordance with the present invention offers, amom others, the following fundamental advantages in comparison withthe lower ranges hitherto used in practice. vThe number of talks-and other communications to be one line ls practically unlimited. l'br the'purpose of separating the dierent talks on moduvlated carriers at a receiving point simple selective' ampliiler circuits as provided in ordinary broadcast receiving sets can be used. Owing to ltheirhigh` frequency, the carrier wave currents eiiter but-sllghtlyinto the surfaceof copper wires. Consequently, conductors of the type havinga thin copper coating on a wire, or support,

used as well as solid copper conductors. Thereby the price of 'carrier-lines can be considerably reduced. The transmission and receiving circuits and equipments can be ofthe type as normally manufactured in the broadcast lndustry.

' 'use is therefore not lucrative. Tra and v Consequently, they are so low in price that their use is also economicalin case of transmission of intelligence, including pictures, over short distances where as it is well known equipments for long-waveservice are very expensive and ltheir receiving equipments for use with our invention yare in general easily portable and can therefore ybeusedinvariousiipecialservicsuchastelephonein trains, military or policepurposes, etc. By meansof bleh-frequency ampliiiers tuned to the carrier waves by means of oscillatory circuits, a hihly elective intermediate `amplification can tance obtainable is practically unlimited Iii-in a multiple transmission of intelligence a thesametime over thesame line by means of carrier waves of dierent high frequencies within the range vof lthe present inventioneachofthesecarrierwavesrepresentsasocalled individual channel through which the neouslytransmittedindivldnalchannelsormodulated carrier wavescaneasilybeseparatedat thereoeiverstatlonbymeansofselectivetimed three-electrode tubes in known electricaiarrangement to generate -high frequency carrier oscillations `upon which are modulated inuencing' currents representative of intelligence and of any frequency, from lowfrequency up to a frequency as high as e. g. currents which 'reproduce pictures, i. e. of thetelevision range. 'lbe thus modulated carrier waves having a frequency withintherangeoftheinventionaretrammitted` over non-concentrical and spaced apart. wires indicated in the drawing by dotted line representative of such cable or open-wire lines. or of a combination thereof. Obviously this line is aperiodical, i. e. not. timed to the particular frequency of the carrier wave used. '111e receivingsetmaybeanordinarybroadcastingreceiver comprising a selective tunable amplifier circuit coupled by condensers with the line. But there mayalsobeusedinsuchareceiversetaspeclal connectionasshownbyestablishedsymbolsin Pig. 2 which do not need any further explanation.

Without limiting the broad scope ofthe invention as covered by the appended claims, to illustrate by way of example the nature of our invention in that it comprises the transmission of intelligence including messages, signals and pictures (television) along substantially aperiodical open-air lines over great distances. suchas 'ml1es, 125 miles and more, up to about 300 and 400 miles and more, using carrier waves including .frequencies of kilocycles up to about 10,000 kiloeyeles, and more, should a signal energy of e. g. about 3 'watts be used. In case greater distances, causing corrpondingly hither attenuations, are tobe bridged over, an intermediate amplification may be suitably provided for by using an amplifier with selective input circuit tuned to the carrier wave and coupled tothe lines e. g. by suitable condensers. Should our invention be used in connection with Asubstantially aperiodical cables or trunks, distances up to 30 -miles and more. can easily be served using carrier wave frequencies of 85 kilocycles and more, including upto about 3000 kilocycles, and operating with a signal energy of e. g. about 3 watts.

In every such casethe input circuit of the .ampliner at the receivingy point simply has to be tuned to the carrier wave frequency. which is to be received thereby.

VIt is to be understood that the invention is not limited to any exempliilcation given hereinbefore.

the appended claims.`

what is claimed is: I

l. A method ofi-transmitting lisnals and communicatiousl of low frequencies up to khigh frequencies including the television range along -but is to be derived in its-'broadest aspectrrom laperiodical communication lines of the type com# Pricing non-concentrical conductors with modu- 2. A method of transmitting signals and coin-v munications of low frequencies up to high frequencies including the television range along aperiodical communication lines of the typecomprising spaced apart non-concentrical conductors with modulated carrier frequencies in the range of and above 85 kilocycles over distances corresponding to an attenuation of about 4 or more Neper at the carrier frequency used.

3. A method of transmitting signals and communications of low frequencies up to lhigh frequencies including the television range along communication lines of the type as ordinarily used for telephone and telegraph communication and comprising aperiodical spaced apart nonconcentrical conductors, with modulated carrier frequencies in the range of and above 85 kilocycles over distances corresponding toan attenuation of about 4 or more Neper at the carrier frequency used.

4. A method of transmitting intelligence of low frequencies up to high frequencies including the television range along communication lines comprising aperiodical open-wire lines with modulated carrier frequencies in the range of and above 85 kilocycles over distances corresponding to an attenuation of about 4 or more Neper at the carrier frequency used.

5. A method of transmitting' intelligence of low frequencies up to high frequencies including the television range along communication lines comprising aperiodical spaced apart non-concentrical cable lines with modulated carrier frequencies in the range of and above 85 kilocycles over distances corresponding to an attenuation of about 4 or more Neper at the carrier 'frequency used.

6. In a method of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point employing selective amplifier circuits at the receiving point; the transmission of modulated carrier waves over wires comprising aperiodical wires within the high frequency range above and including about 85 kilocycles and 'over distances where the signal level substantially surpasses the noise level.

'7. A method of multiple transmission of intelligence of low frequencies up to high frequencies including the .television range along communication lines with modulated carrier frequencies forming individual channels over distances corresponding to an attenuation of .about 4 or more Neper at a carrier frequency used, said lines substantially comprising aperiodical open-wire lines, selecting said carrier frequencies within a range of about 85 to about 10,000 kilocycles. and separating the individual channels by tuned amplifier circuits at the receiver station.

' 8. A method of multiple transmission of intelligence of low frequencies up to high frequencies including the television range along communication lines with modulated carrier frequencies forming individual channels over distances corresponding to an attenuation of about 4 or more Neper at a carrier frequency used, said lines substantially comprising aperiodical spaced apart non-concentrical cable lines, selecting said carrier frequencies within a range of about 85 to about 10,000 kilocycles, and separating the individual channels by tuned amplifier circuits at the receiver station. 9. A method of multiple transmission of intelligence of low frequencies up to high frequencies including the television range along communication lines with modulated carrier frequencies forming individual channels over distances corresponding to an attenuation of about 4 or morev Neper at a carrier frequency used, saldlines substantially comprising aperiodical open-wire lines,

-selecting said carrier frequencies within a range of about 85 to about 10,000 kilocycles, separating the individual channels by tuned amplier circuits at the receiver station, and removing local weaknesses in reception, if occurring, by slight alterations of the carrier frequency or by tuning of the receiver.

' 10. A method of multiple transmission of intelligence of low frequencies up to high fre quencies including the television range along communication lines with modulated carrier frequencies forming individual channels over distances corresponding to an attenuation of about 4 or more Neper at a carrier frequency used, said lines substantially comprisingaperiodical spaced apart non-concentrical cable lines, 'selecting said carrier frequencies within arrange of about 85 to about 10,000 kilocycles, separating the individual channels by tuned amplifier circuits at the receiver station, and removing local weaknesses in reception, if occurring, by slight alterationsV of the carrier frequency or by tuning of the receiver.

11. In amethod of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point employing selective ordinary broadcast receivers at the receiving point: the transmission of modulated carrier waves over aperiodical wires within the high frequency range where the signal level substantially surpasses the noise level and over distances the attenuation of which exceeds about 4 Neper at said carrier frequency.r

l2. In a method of wiredwireless transmission of intelligence of low frequencies up to high frequencies including the television range from point tov point employing ordinary selective broadcast receivers at the receiving point, the transmission of waves over aperiodical lines substantially comprising cable wire lines, as ordinarily used for telephone and telegraph communication, in the frequency range of or above 85 kilocycles and over distances vthe attenuation of which exceeds about 4 Neper at said frequency.

13. In a. method of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point employing ordinary selective broadcast receivers at the receiving point, the transmission of waves over aperiodical lines substantially comprising open-wire lines, as ordinarily used for telephone and telegraph communication, in the frequency range of or above 85 kilocycles and over distances the attenuation of which exceeds about 4 Neper at said frequency.

14. In a method of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point employing tunable selective amplifying receives at the receiving point, the transmission of carrier waves over aperiodical lines substantially comprising cable wire lines, as ordinary used for telephone and telegraph communication, in the frequency range from about 85 kilocycles up to about 10,000 kilocycles, said wired transmission carried over distances the attenuation of which exceeds about 4 Neper at said carrier frequency.

irlnametlmdofwiredwirelesstransmission of intelligence oi' low frequencies up to high frequencies including the television range from point i s to point employing tunable selective amplifying receivers latthe receiving point, the

of carrier waves over 'aperiodical lines substantiaiiy comprising open-wire lines. aswordinarily t ined for telegraph and telephone communication. lo inthefrequencyrangefromabout kilocycles e upto about 10,000 kiiocycles. said wiredtrans-r carried over distances the attenuation cf which exceeds about 4 Neper at said carrier frema. v'

ls v1li. m s method orwirca wil-dess transmission.

ci' intelligence of low lfrequencies up to high frequencies including l the television range from point to point employing selective ampliiiervcircuits at the receiving point: the transmission of 30 modulated carrier waves over lines comprising aperiodical open-wire lines within the high-frequency range above and including about zkilocyclesand over distances where the attenuation level of. said line at the carrier frequency-apu preaches or surpassesthe noise'levelof said line atthecarrierfrequencvm` .y 17. In a method ofwired wireless transmission of inteliigenceoflowfrequencies up to high frequencies including the television range from point l0 tcpcint'empicyinsfseiective ampliacicircuits at the receiving-point:` theftiansrnission of modurlated carrier waves'over flines comprising spaced apart non-concentrical cablev lines A'within i the l high-frequency range above `and including 'about 35 05 kiiocycles and over dlstancesvwhere theattens uation level of said line at thejcarrier frequency approaches or surpasses the noise level of said line at the carrier frequency. i `1.0. Asystem of wired wireless transmissioncof intelligence of low frequencies up to high frequencies including kthe television range from point vto point'comprising atransmitting circuit `itt* one point for modulatedl carrier waves, a viselec i tive amplifier circuit for receiving said carrier dl waves at anotherfpoint; `said transmitting and said receiving circuits coupled to a line of the type comprising aperiodical non-concentrical conductom said can'ierwaves'being in the range above and `including about 85 kilocycles where'the atn tenuation level .of said line` at the carrier frequency approaches or surpasses the noise level cf said line at the carrier frequency.

10. A system of wired wireless transmission of: intelligence of low frequenciesy up to high frequencies including the television rangefrom point to point comprising a rtransmitting circuit at one point for modulated carrier waves inthe range of and above 85 kilocycles. a selective ampliercircuit for receiving said carrier wavesrat4 l). anotherpoint. said transmitting and said receivf' ing circuitslcoupled to a lineof the type comprising aperlodical non-concentrical conductors. said carrier proceeding from said transmitting circuit tovsaidreceivingeircuitalong said line over a es distance causing yan attenuation of and exceed- Neper at said carrier frequency. 20. Asystemofwiredwireless noi intelligence ,of lowv frequencies up to high frequencies including ,Y the television range Vfrom 7s nantis `point comprising Vsi transmitter st cnc g point modulated carrier waves within the fre-f cycis, a selective ordinary broadcast receiver-for said rrier waves at another point. said transquency.

stantially comprising an aperiodieal open-wire line,said tosaid-receiveralongsaidwii'elineover aiis-` tance causing an attenuaticnexceedingaboutl Neper atsaidcarrierfrequency.

21.1Asystem cf wired-wireless transmision of intelligence of low upto highfrequencies including thetelevisicn range from point topoint compxisingatransmitteratonepointfor.

carrier waves within the frequency 10 range from about 86 utoabout 10.000 kiiocycln. a selective ordinary broadcast receiver forsaid carrier waves latanother point, said transmitter and said receiver coupled to a line substantially. comprising an aperiodical non-concentrioalil spacedapart cable wireline asordinarily forv telephone or telesraph communication.` said carrierproceedingifrom said transmitter to said receiver'alongsaid wine lineover a causing an attenuation exceeding valilcut ,4 Neper 80 atsaid carrier frequency.r yi' 21A system ofwiredvwireleas intelligence. of ylow .frequencies up to high frequencies including the `television range fran.

point to 'point comprising a' transmitting circlt- 2li` at one point for carrier waves upon which said intelligenceis `modulated,` a` selective amplifier i circuit for receiving said'carrier waves at another point, said transmitting and said'. receiving geircuits coupled to a lineoi' the', type 3 aperiodicai open-wire lines. saidV circuits tuned to a carrier-high frequency and spaced from each.` other so that the attenuation level of said lineat the carrier frequencyfapproaches ,ori surpasses the noise level oi' said lineattire carrier, fre- 35 quency.

23. A system of wired wireless transmisaionof intelligence of low ,frequencies up to quenciesincluding the television-range from poirity to point comprising atrannnitting circuit at one, 40 point for carrier waves `upon which said nintelligence is modulated, a selective amplifier circuit for receiving said `carrier'waves at another point.' said transmitting and'said receiving cir'- cuitscoupled to;a line ofthetype comprising 4s frequency approaches or surpasses the noise level so to point comprising a transmitting 'circuitat one ss point for kmodulated carrier`- wavespa` selective: ampliiler circuitfor receiving said carrlerfwaves at another point, said transmitting and said re-,

ccivmir circuits coupled to sunset tnetype cmi:-`

prising aperiodical non-concentrical `conductors n and tuned to a carrier yhigh frequency vin the range where 'the attenuation level of said line at thecarrier frequency approaches or t the noise levelk of said line at ,the carrier fre- `intelligence of low frequencies up to high point for carrier waves upon which said 'intellifw gence ismodulated,'as elective amplificaI circuit for Y mcsivingssidcarrierwsvesstanctnsrpoinesaai transmitting and said receiving circuits coulled to alineofthetypecomprising aperiodical nonconcentrical conductors. said circuits tuned to a 1g carrier high frequency and spaced from each other so that the signal level substantially surpasses the noise level at the carrier frequency.

26. A system of wired Wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point comprising a transmitting circuit at one point for carrier waves upon which said intelligence is modulated, a selective amplifier circuit for receiving said carrier Waves at another point, said transmitting and said receiving circuits coupled to communication lines of the type as ordinarily used for telephone and telegraph communication and comprising aperiodical spaced apart non--concentrical conductors, said transmitting and said receiving circuits tuned to a carrier high frequency arid spaced from each other so that the signal level substantially surpasses the noise level.

27. A system of Wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point comprising a transmitting circuit at one point for modulated carrier waves, a selective amplifier circuit for receiving said carrier waves at another point, said transmitting and said receiving circuits coupled to a line of the type comprising aperiodical non-concentrical conductors and tuned to a carrier high frequency in the range where the attenuation level of said line at the carrier frequency approaches or surpasses the noise level of said line at the carrier frequency, the distance of said transmitting and said receiving circuit being such that the attenuation caused by said line amounts to or exceeds about 4 Neper at the carrier frequency.

28. A system of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point comprising a transmitting circuit at one point for carrier Waves upon which said intelligence is modulated, an ordinary selective broadcast receiver at the other point, said circuit and said receiver coupled to a line substantially of the type as ordinarily used for telephone and telegraph communication andcomprising non-concentrical spaced apart conductors, said circuit and said receiver tuned to carrier frequencies exceeding about 85 kilocycles and spaced from each other so that the attenuation caused by said line between said circuit and said receiver equals or exceeds about 4 Neper at a carrier frequency.

29. A system of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point comprising a transmitter at one point for modulated carrier waves within the frequency range from about 85 to about 10,000 kilocycles, a selective ordinary broadcast receiver for said carrier waves at another point, said transmitter and said receiver coupled to a line substantially ccmprising an aperiodical open-wire line as ordinarily used for telephone and telegraph communications, said transmitting circuit and said receiving circuit spaced from each other for a distance causing an attenuation exceeding about 4 Neper at said carrier frequency.

30. A system of wired wireless transmission of intelligenceof low frequencies up to high frequencies including the television range from point 31. A system of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point .to point comprising a transmitting circuit at one point for carrier waves upon which said intelligence is modulated, an ordinary selective broadcast receiver at the other point, said circuit and said receiver coupled to a line comprising aperiodical non-concentrical conductors, said circuit and said receiver tuned to carrier frequencies exceeding about 85 kilocycles and spaced 'from each other so that the attenuation caused by said lin-e between said circuit and said receiver equals or exceeds about 4 Neper at a carrier frequency.

32. A system of multiple wired Wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point comprising transmitting circuits at one point for carrier waves upon each of which intelligence is modulated, selective tunable amplifier circuits for receiving said carrier waves prising aperiodical spaced apart non-concentrlcal conductors, said transmitting circuits capable of transmitting high carrier wave frequencies different rfrom and not interfering with each other, each of said receiving circuits tunable to one of said carrier frequencies thereby separating them from each other, said transmitting and receiving circuits `tuned to carrier high frequencies of about and exceeding 85 kilocycles and spaced from each other so that the attenuation caused by the line between said points equals or exceeds about 4 Neper at a carrier frequency.

33. A system as described in claim 32, said line comprising aperiodical open Wire lines.

34. A system as described in claim 32, said line comprising aperiodical spaced apart non-concentrical cable lines. A

35. A system of wired wireless transmission of intelligence of low frequencies up to high frequencies including the television range from point to point comprising a transmitting circuit at one point for modulated carrier waves in the range of and above about 85 kilocycles, a selective amplifier circuit forY receiving said carrier waves at another point. said transmitting and said receiv-

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