US1976910A - Multiple radio receiving system - Google Patents

Description

LMA 3 Oct. 16, 1934. E v MY Er AL 1,976,910

MULTIPLE RADIO RECEIVING SYSTEM Filed D80. 4. 1929 PIC-3.2

5 I", RADIO RECEWER ta I20 6 RADIO RECEIVER fr'fiwiifi '12 BY Ju/m: C. flceve: (1% ,1, 6? m ATTORNEY OR IN 343/846 Patented Oct. 16, 1934 UNITED STATES MULTIPLE RADIO RECEIVING SYSTEM Ernest V. Amy and Julius G. Aceves, New York, N. Y., assignors to Amy, Aceves 8: King. Incorporated, New York, N. Y., a corporation of New York Application December 4, 1929, Serial No. 411,435

10 Claims.

This invention relates to a multiple high frequency or radio receiving system for operating a plurality of high frequency receivers oi! the same pickup device with minimum interference or interaction between said receivers, and is particularly applicable to simultaneous operation of a number of radio receivers operating from the same antenna, as for. example, in the case of an apartment house or hotel where a single antenna 10 is provided to which a number of radio receivers are connected. More particularly this invention is an improvement on the system disclosed and claimed in our copending application, Serial No. 357,652, filed April 24, 1929, entitled Multiplex receiving system", to which reference may be had for an understanding of the more fundamental aspects of our system.

In the application above-referred to we have disclosed a system in which there is provided an antenna and a lead-in extending to a plurality of radio receivers to be served by said antenna and finally to ground through a terminating resistance. In the said application we disclose a meth- 0d and apparatus for loading the lead-in conductor in such a manner that interference or interaction betweenthe various receivers connected to the lead-in are minimized. This is done by interposing loading coils in the lead-in or line conductor between the receivers and interposing between the antenna terminal of the receiver and the leadin or line conductor a condenser, the coils and condensers having certain constants as therein pointed out. The lead-in conductor is loaded in such a manner that it acts as a uniform attenuation line, the top frequency of which is equal to T-VLC and is terminated at ground through a terminal It is an object of this invention to provide a system of the class described, wherein the lead-in or line conductor may be installed entirely within the building, except for such initial portion as may be required from the antenna to the point of entry into the building.

It is a further object to provide a system of the class described in which the lead-in may be run .through conducting protective grounded conduit without serious interference with the operation of the system, or without serious loss of efllciency. It is a further object of this invention to'provide a system of the class described wherein maximun; energy. delivery from the antenna to any point in the line is obtained, and wherein the lead-in conductor or transmission line acts as a uniform attenuation line passing with substantially equal efflciency all frequencies desired to be received, even though the line runs within a conducting conduit.

It is a further object of this invention to provide a system of the class described in which the lead- 55 in or transmission line and its leading coils are protected from picking up interference while maintaining the desired transmission characteristics as fully as possible.

It is still a further object of our invention to provide a system of the class described in which the necessity of carrying the lead-in through the exterior wall of the building for each receiver is eliminated, and the appearance of the system is improved and in which the risk of installation is 7 reduced by the elimination of the necessity for working on the outside of the exterior walls of the building.

It is still a further object of this invention to provide a system of the class described in which 90 additional signal energy may be introduced into the lead-in or line conductor throughout its iiegigth to compensate for energy losses in the Still other objects and advantages of our invention will be apparent from the specification.

The features of novelty which we believe to be characteristic of our invention are set forth with particularity in the appended claims. Our invention itself however, both, as to its fundamental principles and as to its particular embodiments will best be understood by reference to the specification and accompanying drawing, in which I is a diagrammatic view of the complete syst m:

Fig. 2 is a perspective view of the outlet box with a loading unit in position showing the cover removed, and Fig. 3 is a circuit diagram of a modified form.

Referring now more particularly to Fig. 1, 1 designates an antenna or pickup device which may, for example, be installed upon the roof of the apartment house or hotel. A suitable lightning arrester may be connected between the an- 1 5 tenna and, ground as shown atically. 2 designates a lead-in or line conductor, and 3 indicates diagrammatically a form of conduit within which the line conductor 2 is carried.

4, 5, 6 and 7 designate outlet boxes of a type similar to thme customarily used in the installation of electric-light wiring. 9 and 10 are radio receivers of any usual type such as are likely to be found in the hands of the users. While we .have indicated only two radio receivers, it will be understood that this is merely for convenience of illustration and that additional radio receivers may be provided if desired. Within the outlet boxes 5 there is provided a coupling unit which is designed as will'be more particularly pointed out herein, and which for example, may have the form disclosed and claimed in the copending application of Ernest V. Amy,filed June 19, 1929, Serial No. 372,177, entitled Multiplex receiver system." The coupling unit consists of a pair of coils 11a and 11b connected in series and also preferably comprises a condenser 11c,

one side of which is connected to a point electrically intermediate the coils 11a and 11b. The other terminal of the condenser 110 is connected to the antenna terminal of the radio receiver 9 and the ground terminal of said receiver is comnected to the outlet box 5. Since the precise manner of this connection per se forms no part of our invention, it is not described in detail. It is believed that it will suflice to say that a cover plate is provided for the outlet box 5 which cover plate may carry a pair of terminals to which the user may connect the antenna and ground terminals of his receiver; the terminals on the cover plate being appropriately marked and the aerial terminal being insulated from the cover plate and from the outlet boxes and connected to one terminal of condenser 11c as already stated.

' The ground terminal on the cover plate is preferably directly connected to the cover plate and to the outlet box. The arrangement is indicated more particularly in Fig. 2 wherein the outlet box 5 is shown partly cut away with the connecting unit comprising coils 11a and 11b and condenser 110 shown in dotted lines in position therein. It will be noted that three leads C1, C2, C3 extend into the unit. Leads C1 and C2 are connected to the incoming and outgoing sides of the transmission lines whereas lead C3 is connected to the aerial terminal of the cover plate. No lead is ordinarily necessary for the ground terminal of the cover plate, connection being established when the cover is fastened in position. We have shown the outlet box as also being supplied with a light orpower outlet 0 of standard form, energized from supply leads L1 In, of the house power system. Connection for energizing the radio receiver may be made to said outlet.

We have found that the so-called BX cable ordinarily used in installing electric-light wiring within buildings is not as satisfactory for our purpose as unitary solid piping, for example. ordinary iron pipe. It is necessary, however, if best results are to be obtained, to provide good electrical contact between joints in the conduit and for this reason it is advisable to provide bonds 15 electrically joining the separate sections of conduit, and this is true even though mechanical connections are made between said sections as for example by means of threaded joints, since ordinarily the resistance of such joints may be so high as to interfere with the operation of our ystem.

The conduit system is grounded as at 8 and it will therefore be seen that there will exist a considerable distributed capacity between the lead-in conductor 2 and the conduit and between the various coils and conduit. We have found that in using piping approximately 1" in diameter and using No. 12 copper wire for the lead-in, this capacity may amount to 8 m. m. f. per foot. This may be compensated for by reducing the capacity in the coupling units, that is the capacity 110, 12c, etc. from the value they would have if the conduit were not used.

Under certain conditions, also, it is possible that due to imperfect dielectric and due to eddy currents in the piping the impedanceof the line may be much smaller than the value obtained by calculation, using the formula Ifthisisthecaseandiftheantennausedhas a very large impedance, it is desirable to interpose between the antenna and the beginning of the transmission line an auto-transformer such as shown at 16 in outlet box 4. The lead-in conductor terminals 17 and 18 are preferably both variable so that the best adjustment for each may be obtained by trial in the particular case. Also in terminating the line, while theoretically it should be terminated or grounded through a resistance equal to if the line has considerable energy dissipation due to the eflective resistance introduced by the piping and by the radio receivers, it may be found desirable to terminate the line through a resistance 30 somewhat higher than that given by but not greatly different. In practice we have found that a terminal resistance of 1,000 ohms is satisfactory with aline in which is equal to 517. Under certain conditions it may be desirable to provide an inductance 31 as well as a resistancein the termination unit. This will be the case particularly when the dissipation of energy along the line is relatively high. It is also to be noted that the line in its conduit may be regarded as a double wire transmission line, the conduit acting as a return circuit and ground for the radio receivers. This has a tendency to neutralize the self-induction of the line per unit length and therefore the inductance of the coupling units may be increased somewhat over the theoretical value to compensate for this factor.

The construction of the auto-transformer 16 should be such that there is a minimum amount of magnetic leakage from primary to secondary as otherwise there will not be as much transfer of energy from one side to the other as would'be the case if the transformer were not used, and under this condition the energy transfer will be a function of frequency which is undesired, it being of course desirable to have no substantial difference in the performance of the transformer over the frequency band to be transmitted as, for example, the present broadcast band. While in general it is desirable to wind the coil 16 in such -a manner that the tightest possible coupling is obtained between primary and secondary yet under certain conditions, if desired, a certain amount of leakage reactance may be provided between these windings to partially neutralize or compensate for the capacity reaction of the antenna over a narrow band of frequencies.

Under certain conditions, as for example, in th case of very tall buildings. or under conditions where the dissipation of energy in the line conductor 2 is unusually high it may be desirable to provide within the conduit a direct low resistance path to ground, and means for introducing additional high frequency energy into the line at points relatively far removed from the antenna. We find that this latter may be very satisfactorily done in the following manner.

We may provide an auxiliary antenna 20 which is preferably so located with respect to the main antenna 1 that the antenna 20 does not deprive the antenna 1 of any energy which it may otherwise pick up. For example, the antenna 20 may be located on a different part of the roof of the building from the antenna. 1 and may be strung at an angle thereto. A separate down-lead 21 is provided for the antenna 20. This down-lead is carried through the conduit 3 in which the downlead 2 is carried and may extend the entire length of the down-lead 2 and is grounded through a resistance 22 which has a value of approximately 1,000 ohms, the resistance 22 serving to drain of! static charges and the like. For best results, this additional down-lead should be loaded in a manner similar to down-lead 2.

It will be apparent, however, that in cases where it is not a disadvantage to have the antenna 20 electrically floating the lower end of the downlead 21 may be left free. Also it will be understood that if desired. the antenna 20 may be tuned by means of a tuning circuit of any well-known type associated with the antenna or with the down-lead. Preferably the tuning circuit is placed at the lower end of the down-lead 21 and is indicated diagrammatically by the variable inductance 23. In case difficulty is found in receiving signals of a particular frequency the antenna 20 may be sharply tuned to this frequency. thereby increasing the pickup of energyof that frequency or if desired, the various arrangement shown and described in the first application above-referred to may be utilized. If it is merely desired to increase the pickup over the entire broadcast band or a part of it, the tuning may be less sharp.

It will be apparent that since the down- leads 2 and 21 are run in the same conduit and are necessarily closely adjacent to each other, there will exist capacity coupling between these downleads and by reason of this coupling energy will be transferred from the down-lead 21 to the down-lead 2. This transfer of. energy will be distributed since the capacity is distributed. It will be understood, however. that if it is desired to cause this energy transfer to take place to a greater extent at a particular point, this may be done by increasing the capacity between these leads at such point as by connecting them through a capacity of the desired size.

Also it will be understood that if desired, in

stead of utilizing the conduit itself as a ground for the various radio. receivers an additional ground wire may be rim through the conduit 3, or the down-lead 21 may be utilized as the ground lead. in case the auxiliary antenna 20 is not employed. In installing our system we prefer to provide two wires within the conduit 3. one of which is utilized as the down-lead 2 and the other of which is utilized as the ground wire, as shown in Fig. 3.- This ground wire is preferably connected at its upper end to the low side of the secondary of autotransformer 16 and at its lower end directly to a low resistance ground. In such case, a direct connection from the said ground wire is made to the ground terminal of the various radio outlets. 1

While we have shown and described certain preferred embodiments of our invention it will be understood that modifications and changes may be made without departing from the spirit and scope of our invention as will be understood by those skilled in the art.

Weclaim:

1. In a multiple: high frequency receiving system for operating a plurality of receivers from the same antenna, a line conductor connected to said antenna a plurality of radio receivers connected to said line conductor and ground. loading coils interposed in said line conductor between said receivers and means interposed between said antenna and said line conductor for matching the impedances thereof.

2. In amultiplex high frequency receiving system for operating a plurality of receivers from the same antenna, a line conductor connected between said antenna and ground, a plurality of radio receivers connected between said line conductor and ground. loading coils interposed in said line conductor between said receivers, and a transformer connecting said antenna and said line conductor. said transformer having its constants so chosen as to match the impedances of said antenna and line conductor.

3. In a multiplex high frequency receiving system for operating a plurality of receivers from the same antenna, a line conductor connected between said antenna and ground. a plurality of radio receivers connected between said line conductor and ground. loading coils interposed in said line conductor between said receivers, and an auto transformer connecting said antenna and said line conductor, said transformer having its constants so chosen as to match the impedances of said antenna and line conductor.

4. In a multiplex high frequency receiving system for operating a plurality of receivers from the same antenna, a line conductor connected between said antenna and ground, a plurality of radio receivers connected between said line conductor and ground, a second antenna, a line conductor connected thereto. the last-mentioned line conductor being positioned closely adjacent said first line conductor during at least a portion of its length.

5. In a multiplex high frequency receiving system for operating a plurality of receivers from the same antenna, a line conductor connected between said antenna and ground. a plurality of radio receivers connected between said line conductor and ground. a second antenna. a second line conductor connected to said second antenna. said line conductors being positioned closely adiacent and capacity coupled to at least a portion of their length.

6. In a multiplex high frequency receiving system for operating a plurality of receivers from the same antenna, a line conductor connected between said antenna and ground, a plurality of radio receivers connected between said line conductor and ground. a second antenna, a second line conductor connected thereto. both said line conductors being enclosed during at least a porradio receivers connected between said line conductor and ground, loading coils interposed in said line conductor between said radio receivers, a second antenna, a second line conductor, said 5 line conductors being so arranged that energy from said second antenna is ted into said first line conductor at several portions thereof.

8. A multiplex high frequency receiving system for operating a plurality of receivers from the same energy pickup device, comprising, in combination, means for picking up high frequency energy to be received, a transmission line associated with said pickup means, said line being positioned within an enclosing conductor through at least a portion of its length and being loaded at predetermined points to act as a uniiorm attenuation line passing energy up to the highest desired frequency; a ground conductor positioned withinsaid enclosing conductor through at least a. portion or its length and a plurality of receivers coupled to said line at points electrically intermediate to said loaded points and coupled to said ground conductor.

9. In a multiplex high frequency receiving system for operating a plurality of receivers from the same antenna, a line conductor connected to said antenna. a ground conductor connected to said ground, a plurality of radio receivers connected to said line conductor and ground conductor, loading coils interposed in said line conductor between said receivers and means interposed between said antenna and said line conductor tor matching the impedances thereof.

10. In a multiple: high frequency receiving system for operating a plurality of receivers from the same antenna in combination. an antenna, a ground, a line conductor connected between said antenna and ground, a ground conductor connected to said ground, a plurality of radio receivers connected between said line conductor and said ground conductor and loading. coils interposed in said line conductor between said receivers, said line conductor and said ground conductor being positioned through at lest a portion of their length within a metallic conduit.

ERNEST V. AMY. JULIUS G. ACEVES.

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