US1976909A

US1976909A - Multiplex receiver system

Info

Publication number: US1976909A
Application number: US357652A
Authority: US
Inventors: Ernest V Amy; Julius G Aceves
Original assignee: Amy Aceves & King Inc
Current assignee: Amy Aceves & King Inc
Priority date: 1929-04-24
Filing date: 1929-04-24
Publication date: 1934-10-16
Anticipated expiration: 1951-10-16

Description

jTI'OSS Reference E Oct. 16, 1934. E} v. AMY ETAL 1,976,909 I MULTIPLEPX REbEIVER SYSTEII Filed April 24, 1929 2 Sheets-Sheet l FIG. 1 RECEIVER REC.

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REC.

INVENTOR M I ATTORNEY Examinel Cross HgEi-arence E. v. AMY ET AL MULTIPLEX RECEIVER SYSTEM Oct. 16, 1934.

2 Sheets-Sheet 2 Filed April 24, 1929 FIG. 5

REC.

REC

' INVENTOR ERNEST v. AMY AND BY JULIUS amzvzs \ATTORNEY aUNlTED sTATEsPATENT OFFICE I MoLrrPLEx RECEIVER SYSTEM Ernest V. Amy and Julius G. Aceves, New York,

1. York N. Y., assignors to Amy, Aceves & King, Incorpcrated, New York, N. Y., a corporation of New e Application'April 24, 1929, Serial No. 357,652

, This invention relates to a multiplex high frequency receiving system for operating a plurality of high frequency receivers from the same pickup device with minimized interference or in- 1;. ter-action 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 ease of an apartment house or hotel, where a single antenna .10 is provided to which a number of radio receivers are connected.

, Heretofore, in cases where it is desired to operate a considerable number of receivers in the same building, as for example, in the case of apart- 11 ment houses, hotels and the like, in which there {3- ber of aerials by individuals, each one of whom are or may be a considerable number of radio receivers, it has been customary for each operator to provide his own antenna and lead-in system connected to his receiver. The antennas are usu- 'Ifg ally erected upon the roof of the building, and

usually this results in the erection of a consid- Ierable number of aerials in adjacent positions in which the coupling between the aerials is so great that the operation of any receiving set Can- .5 2 nected to one aerial is materially affected bythe operation of another set connected to an adjacent aerial.

In addition to interference between receivers soconnected and operated, the erection of a nummay have different ideas" of construction, disfigures the building and may even result in property damage to the building and actual danger to the tenants if, for example, the aerials are not properly grounded and protected against lightning.

It is an object of this invention to provide a system whereby a number of receivers may be operated from the same antenna.

.- I It is a further object of this invention to provide a system whereby a number of receivers may be operated from the same antenna and may be tuned to different frequencies, the system being so arranged that a variation of tuning of one receiver will not change the signal voltage fed tenna by a greater percentage than if the second receiver were operated on its own aerial under 7 in which each of the receivers connected tothe antenna is fed with a signal having a strength .55 as good rbetterthan the receiver would obtain 2 Claims. (01. 250-9) to another receiver connected tothe same anif it were fed by its own antenna under the conditions hereinbefore described. f, .It is a further object of this invention to provide a system of the class described, in which the lead-in conductor may pass from floor to floor or may pass to a plurality of receivers located on the same floor without introducing undesirable effects from one receiver to another, as already pointed out.

It is a further object of this invention to provide 4 a system of the class described, in which the leadin conductor acts as a uniform attenuation line passing all frequencies of the band desired to be received by any receiver connected thereto, and which is so arranged as to prevent the production 21 0 of standing electrical waves upon the lead-in conductor.

It is a further object of this invention to provide a system of the class described which may be so arranged as to reduce the strength of sig- 2 :5 nals of any particular frequency fed to the associated receivers.

1 will best be understood by reference to the sped-.

fication and accompanying drawings, in which like reference numerals indicate like elements,

-and in which: 1

ing the preferred method of coupling a single receiver to the transmission line or lead-in con- Figure 3 shows, diagrammatically, a modifiedarrangement according to our invention, and

Figures! and 5 show still further modified forms of our invention.

In its fundamental aspect our invention comprises a pickup device such as an antenna, which may, for example, be mounted upon the roof of the building, provided with a lead-in conductor passing from floor to floor and, if desired, to a plurality of locations upon one or more floors. .-,A

number of radio receivers are coupled to said'iIO The intermediate loading coils preferably all have substantially equal inductance, while the initial and final loading coils preferably have'an inductance equal to one-half that of the inter mediate loading coils.

For the purpose of preventing standing waves on the transmission line, the end of the line or lead-in is preferably connected to ground through a resistance equal to the terminal or surge impedance of the line, that is While we do not desire to limit ourselves to particuiar constants, we have found that very satisfactory results are obtained in broadcast receivers when the intermediate loading coils have inductances of micro-henrys, the initial and final loading coils inductances of 40 micro-henrys, and the coupling condensers for the various receivers have capacities of 250 m. m. f., and the terminal resistance has a value of 400 ohms. Under such conditions the transmission line will pass frequencies as high as 1600 kilocycles, approximately.

Referring now more particularly to Fig. 1: 1 designates the antenna or pickup; 2 the lead-in conductor; -3 and 6 the initial and terminal loading coils, and 4 and 5 the intermediate loading coils. The lead-in conductor 2 is grounded through resistance 7, equal to the surge impedance of the line, and the

various receivers

9, 11 and 13 are connected at their ground terminal to a suitable ground such as the radiator pipe 14 extending through the building, which in turn is grounded as at 15. The antenna terminal of the various rece'vers is connected through

condensers

8, 10

1 and 12, respectively, to-points intermediate the loading coils 34, 45 and 56, respectively.

The insertion of the radio receiver in series with the coupling condenser will change the value both of the resistance and the reactance of the line at that point, but it is desirable that this change bemade so small that the effect on the other receivers will not be greater than-the inter-action which would obtain between such receivers if they were eachconnected to their own antenna mounted upon the roof under the conditions heretofore usual. If the impedance of the receiver is approximately 1000 ohms, the revoltage which issuppliedto the receiver. In general; it-r'nay be'stated that the best values actence of the condenser coupling the receiver to the lead-in conductor should be of the same order of magnitude. Condensers of smalier capacity and loading coils of larger inductance may be used if it is desired to reduce still further the action 'of one receiver on ancther, but it will be understood that this will tend to decrease the signal of inductance and capacity for any particular In installing the lead-in conductor, it is preferable, although not necessary, to install it as shown more in detail in Fig. 2, wherein 18 indicates, diagrammatically, the N floor of the building, and 19 the (N+1) floor. The lead-in conductor 2 is preferably cut at each floor and se- 80 cured in position by means of an insulator 16. The loading coil here indicated as 4 is connected to bridge the gap in conductor 2, formed by the insertion of the insulator 16. The receiver 9 has its ground terminal connected to ground, as for 35 example on the radiator pipe or water pipe, and its antenna terminal connected to one side of condenser 8, the other side of which is connected to the lead-in conductor 2 and the top end of loading coil 4. I

It will be understood that while we have shown a definite number of receivers in the drawings, this is merely by way of example and that the number of receivers connected may be varied.

In the various figures the same reference characters have been used to indicate similar elements, but it will be understood that the constants of such elements will be chosen under any particular condition so as to give the best results.

Referring now more particularly to Fig. 3, we have indicated diagrammatically a system wherein a number of receivers upon the same floor, as well as receivers upon different floors, are 0perated from the same antenna. In this figure (N+1), (N+2) and N+3 represent the various floors, and it will be noted that on the N floor,

receivers

13, 25 and 27 are operated connected to the lead-in 2 by means of condensers 12, 24 and 26, respectively, and separated by

loading coils

20 and 21, respectively.

Referring now more particularly to Fig. 4, we have shown an arrangement which may be utilized when it is desired .to reduce the voltage of any particular frequency fed to the various receivers for any reason, for example if the antenna is located in the vicinity of a powerful transmitter. In this arrangement a trap circuit, consisting for example of inductance 30 and condenser 31 in parallel therewith, may be inserted in series in thelead-in 2 and tuned to the frequency of the signal which it is desired to reduce. In addition, other trap circuits may be inserted at other points if desired; for example, the trap circuit shown as condenser 32 and inductance 33 connected in series may be connected from the lead-in 2 to ground and tuned to the frequency of the signal which it is desired to reduce.

It may also be desired to increase the strength of a signal of a particular frequency, and this. may be done as shown by way of example in Fig." 5. The lead-in conductor 2 may be connected at an intermediate point on inductance 35, which thus constitutes an auto-transformer and is tuned, forexample, by means of condenser 36. One terminal of inductance 35 may be cc-nnected to the grid of an ordinary vacuum tube amplifier 38, while the other terminal of inductance 35 is connected to one end of variable resistance 37, the other terminal of which is connected te o ground and to the'filament of amplifier-38. The operating potential for the plate circuit of amplifier 38 may be supplied by a suitable source of potential 40, preferably connected in series with inductance 39. A tuned circuit, for example in -11 ductance 41, in series with condenser 42, is connected to the commontermin'al of the platen! amplifier 38 and inductance 39 and to the trans mision line 2, and a variable resistance 43'n'1ay be connected between this point and noun-$15 By tuning the

circuit

35 and 36 to the frequency which it is desired to increase, and by properly choosing the values of inductance 35, condenser 36 and resistance 37, and also by varying the position of the tap upon inductance 35, the voltage available on the grid circuit of amplifier 38 is made greater for signals of the frequency which it is desired to increase than for other frequencies, since it will be understood that the potential difference across resistance 37 is impressed across the input of amplifier 38 at all frequencies, whereas voltages of the frequency to which condenser 36 and inductance 35 are tuned are effective only at frequencies at or near resonance. By properly choosing the values of the various variables, such as inductance 35,'condenser 36, resistance 37, and also inductance 41, condenser 42, the desired curve of selectivity may be obtained. More specifically, in the plate circuit the value of inductance 41 and condenser 42 may be controlled with respect to the plate resistance of the tube to give the desired steepness to the selectivity curve.

In this case also we have indicated variable resistance 43 connected between the transmission line and ground. This should be of a value close to the terminal impedance of the transmission for best results.

It will be understood that the antenna itself has certain values of inductance capacity and resistance, and that under certain conditions these may not be the optimum value desired from a theoretical standpoint. Therefore, under certain conditions it may be found desirable to provide a compensating network at the beginning of the transmission line or lead-in conductor 2 for the purpose of matching the antenna and line. However, we find that under most conditions this is not essential and may be omitted.

It will be understood that'in accordance with our invention a number of radio receivers may be supplied from the same antenna, regardless of whether these receivers are located on the same floor or on diiferent floors, or whether a plurality of receivers are located on each floor. It will also be understood that our invention is not limited to any particular type of condenser or loading coil, and, if desired, the loading coil may be formed by winding the desired number of turns directly upon the insulator which secures the adjacent ends of the lead-in conductor.

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.

We claim:-

1. 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 plurality of effectively grounded radio receivers connected through a coupling impedance to said line conductor, and loading coils interposed in said line conductor between said antenna and the first receiver, between said receivers and between the last receiver and ground,

the inductance of all of said loading coils, except the first and last, being substantially equal, and the inductance of said first and last loading coils being substantially equal to one-half the inductance between said receivers.

2. A multiplex high frequency receiving system for operating a plurality of receivers from the same antenna, comprising, in combination, an antenna, a ground, a line conductor connected between said antenna and ground through a terminating impedance, a plurality of radio receivers connected between said line conductor and ground, loading coils interposed in said line conductor between said receivers, and means associated with said system for selectively changing the relation between the amount of energy of a predetermined frequency absorbed by said antenna and delivered to said receivers.

ERNEST V. AMY JULIUS G. ACEVES.