US2487513A

US2487513A - Radio relaying system

Info

Publication number: US2487513A
Application number: US507696A
Authority: US
Inventors: Harold H Beverage
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1943-10-26
Filing date: 1943-10-26
Publication date: 1949-11-08
Anticipated expiration: 1966-11-08
Also published as: GB650446A

Description

New. 8, 1949 BEVERAGE 2,487,513

RADIO RELAYING SYSTEM Filed Oct. 26, 1945 Fig 1.

FRO/7 77/5 WEST 195 Cf VE/ IN VEN TOR.

H rold H. Bel/e rage ATTOB/VEK ther of two terminals troubles due to the quencies in different relay chain.

clude the following transmitting intelligence nals associated with shall be free from Patented Nov. 8, 1949 Harold H.

Delaware Application October 26, 1943,

Beverage, Riverhead, Radio Corporation of America,

N. Y., assignor to a corporation of Serial No. 507,696

- 8 Claims. (Cl. 250- 15) This invention relates to radio relay systems and. is particularly concerned with methods and apparatus for controlling relay stations from eiwhile avoiding feedback use of the same carrier frelinks of transmission in a Where unmanned relay stations are used in an ultra-high frequency communications system,

.feedback difficulties would Occur if the repeating frequency were to reach a remote transmitter having the same or a frequency with which it would cause undesirable heterodyning.

The advantages of using unmanned relay stations in an ultra-high frequency network are well known. Much thought has been directed to the solution of problems relating to radio relaying.

The improvements covered by my invention are set forth with particularity in the appended claims. The objects of the invention itself inas well as others which will be apparent in view of the subsequent detailed description. y A principal object is to provide a relay system using a minimum of equipment and a minimum number of frequencies.

It is a further object to provide a system for through a chain oi unmanned relay stations from either of two termisaid chain.

It is still another object of my invention to provide lock-out means whereby unmanned relay stations when selected for repeating communications from either of two-terminal stations shall not be subject to control by the other terminal station until released.

Again, it is an object to provide a relay system in which the carrier frequencies chosen for linkby-link transmission in a given chain of relays feedback troubles In the description to follow, reference is made :to the accompanying drawings, in which: I

Fig. 1 shows schematically an arrangement of terminal and relay stations, the system being such that a pair of receivers, each operable to receive from a different direction is connected to 9. common transmitter having a two-directional antenna system;

Fig. 2 shows more ment which I preferably in detail a circuit arrangeuse at an unmanned repeating station for selective control thereof irom avoid feedback and west station or at relay having an E-shaped core is substituted for two independent relays 44 and 45 in Fig. 2.

In some of the known relay systems, communications are possible inboth directions simultaneously. Such systems require a considerable number of carrier frequency assignments'in order to "interference singing. In my preferred arrangement feedback is avoided by allocating frequencies to transmitting and receiving equipment at a given repeating station which do not interfere with one another and do not reach to any other repeating station where the same frequencies are used for transmission.

In Fig. 1, the subscripts applied to letters T (for transmitter) and R (for receiver) represent different carrier frequency assignments. The frequencies assigned to the various radio links in the system are represented by wavelength legends the character M represents the operating wavelength on which the transmitter at the west terminal operates and represents the same frequency as that to which the receiver R1 at relay station A is tuned. Transmitter T2 at relay station A uses a carrier frequency represented by the character is to which receivers R2 both at the west station and at relay station E are receptive.

Following through the frequency assignments of the remainder of the relay chain, it will be observed that'transmitter T3 at station B operates on a wavelength M to which receivers Rs at both relay station A and relay station C are receptive.

"Transmitter T1 at station C communicates with length 7&3 sent out by transmitter T3 at the east terminal. I

In order to avoid feedback dilnculties, it is to be understood that station C is located sufficiently remote from the west terminal so that, despite a common frequency assignment, the two transmittel-s T1 are substantially non-interfering. Assume, for example, the effective reach of the signals is 30 miles and that the adjacent stations are 30 miles apart. will be located 66 miles away from the receiver R2 Then the receiver R2 at station B at the west terminal. Both of these receivers are responsive to the-carrier. is, of transmitter T2 at station A, but within the 30-mile radius or station A, no interfering carriers are used either at the station B. Furthermore, any two transmitters which have the same. wavelength assignment are located at least 90 miles apart, as between station A and station D, where the wavelength assignments, A2 of transmitters T2. are the same. Accordingly, my system provides a high degree of freedom from acoustic coupling, termed singing, and other undesirable heterodyning.

As a practical matter, it i found that most of the required relaying of communications by networks of the class described is in one direction only and it is only occasionally that it is desired to relay in the opposite direction. By taking advantage of this fact, a reversible one-way repeater system may be used requiring a minimum number of frequencies. Furthermore, as a practical matter, it becomes unnecessary for one-way reversible systems to duplicate the transmitter equipment at the several unmanned repeater Sta-- tions. Transmitters having bi-directional antenna systems are well known in the art and the use of such antenna systems is contemplated in carrying out my invention.

Referring now to Fig. 2, I shown therein a circuit arrangement which, although capable of modification in various ways, is suitable for remote control of an unmanned repeater station. The receivers R1 and R3 may be considered as differently tuned to signals derived from stations to the west and east, respectively. The transmitter T2 radiates towards stations both to the east and to the west and has assigned thereto a carrier frequency which is shared only by other trans mitters T2 which are sufliciently remote to cause no interference.

Each of the receivers R1 and R3 is arranged to actuate an electronic relay 4| and 42 respectively whenever a response is made to a carrier wave to which the individual receiver is tuned. Electronic relays are well known in the art and any one of a number of different types'of such relays may be chosen for use in the present invention. Preferably such a relay is made responsive to carrier currents, whether modulated or umnodulated. A so-called squelch relay may be used if desired. In this case the incoming carrier wave is rectified and produces a bias potential to be applied to a normally blocked amplifier tube.

When the tube is unblocked it closes a circuit path for operating an electromagnetic relay.

Grid-controlled tubes Whether of vacuum or gaseous discharge type may be used, depending upon the amount of power which is to be switched on and on". The circuit to be switched by relay 4| may be traced from a source of direct current 43 through the winding of an electromagnetic relay 44 and thence through normally closed contacts 46 of relay 45, and through conductor 41 and the space path (not shown) of the electronic relay 4| to ground.v

The circuit controlled by electronic relay 42 may be traced from source 43 through the winding of relay 45, through the normally closed contacts 48 of relay 44 and thence through conductor 49 and the space path of electronic relay 42 to I ground.

The purpose of contacts 46 and 48 is to lock out the operation of one of the relays 44, 45, after the other one has taken control. The un-operated relay must be rendered incapable of upsetting the station control conditions as established by signals first arriving at the repeater station from either terminal. Thus, when relay 44 is actuated, receiver R1 which receives signals from the west is connected to the transmitter T2 and relay having three the modulator of this transmitter is thereupon rendered subject to control only by signals originating at the west terminal. Likewise, when relay is actuated in response to a control carrier wave received on receiver R3, the intelligence by which this carrier wave may be modulated is applied to the modulator of transmitter T2 so as to repeat the signals to a succeeding station further to the west.

Means for applying the traffic signals to transmitter T2 from one or the other of the receivers R1 and R3 will now be described:

The detected signals which are impressed upon the output circuit of receiver R1 may be switched into the input circuit of the modulator in transmitter T2 by energizing coil 50 in a polarized relay so as to throw its armature 5| against contact 20. This establishes the desired connection between the output circuit of receiver R1 and the input to transmitter T2. Coil 50 of the polarized relay is .energized by the closure of contacts 52 on relay 44. This contact closure connects source 43 through coil 50 and thence through the winding of a relay 53 to ground. When relay 53 is energized, the pulling up of its armature 54 connects the positive terminal of a power supply (so labelled) to the tube equipment in the transmitter T2 whereby this transmitter is enabled to radiate a modulated carrier wave.

If reception is first obtained at a given repeater station from a point to the east thereof, then the detected traflic signals received on receiver R3 are applied to the modulator of transmitter T2 by throwing the armature 5| on the polarized relay against contact e. This is accomplished by energizing the coil 55 of this relay. The energizing circuit may be traced from source 43 through contacts 56 of relay 45, the coil 55 and thence through the winding of relay 53 to ground.

It will be apparent that the power supply is fed to the transmitter T2 byenergizlng relay 53 regardless of the source of the signals, or the particular receiver R1, R3 which is for the time being responsive. It is also apparent that once the transmitter T2 is associated with a given one of the receivers R1, R3 for reception from a particular terminal, no interference is possible as a result of receiving signals from the other terminal.

It is true that both receivers R1 and Rs may be allowed to remain in a standby condition in readiness for reception of any signals to which they are respectively tuned, but the tongue 5| of the polarized relay connects the transmitter T2 to only one of the receivers at a time. Furthermore, only one of the remote control relays 44, 45 is operable at anyone time, due to the fact that each of the windings of these relays is in circuit with break-contacts of the other relay. Reversal of fore, possible only after release and de-energizing of the relay which was first actuated.

' A modification of my invention is shown in Fig. 3 wherein it is apparent that the contacts 46, 48, 52, and 56 may be operated by means of a single positions. Such relays are well known in the art and are usually'so constructed that one winding draws the movable contacts against stationary contacts on one side, whereas another winding draws the movable contacts into engagement with stationary contacts on the In a neutral position, the normally 52 ant 56 are open with respect to both sides and the normally closed contacts 46 "and 48 remain normally closed until one or anather of the two coils l4, finisienergizedficirruit connections are not shown in Fig, 3, since theyJmay be-thesame as inFig..2,

Itrwill beapparent to those skilled, in the art that my improvements in radio relay Systems are to be found useful regardless of'the form of intelligence which is transmitted by .way of trafiic signals. Thus the system may be used forpointto-point communications, for broadcasting ofentertainment, whether by. frequency-modulation or amplitude-modulation waves, and alsofor, television and facsimile transmissions: v Itshouldbe; clearly understood that the illustration of Figure l.is given only by way of example and that a lesser or greater number of relay stations may be used as required .by thedistance separating the west and the east terminal sta- Itions. The only requirement isthat the. terminal stations .each have a transmitter and receiver adapted to operate with one of. thejreceivers and transmitters respectively, of the next, adjacent relay station.

. If the distance between the, two terminal stations is so short thatonly one intermediate relay .station would be required, it is apparent that the technique of relaying as hereinbefore described -may, nevertheless, be followed. without modification. Referring again .to Fig. 1,- it will-be seen that stations A and D utilize thesame combination. of frequencies in their respective receivers and transmitters Accordingly, proximity permits, station .A may be situated approximately halfway between the-west andeast terminals and a two-way communicationsystem'would be provided, subject", however, to the condition that the transmitter T2 at the repeater station would be alternatively controlled by its two associated receivers. Suchalternative control would be-sub- .ject to the transmitting times individually appropriated by the west and east transmitters; .'As soon as either terminal transmitter ceases to radiate, the remote control relays of the repeater station are restored to-normal and are made subject toreversal of the relaying direction ,by an incoming signal from the opposite terminal.

For other numbers of relaystations the operating frequencies of the transmitter and receiver at the east terminal may require alteration so that these elements will cooperate with the cor- "responding elements of theadjacent rel y sta tions. '7 V My invention is capable ofmodification in 'many ways to suit practical requirements, as may be found advantageous in-radio relay-systems. =;Such rnodifications will, of course, be understood to be comprehended within the scope of the invention.

I claim:

1. The method of utilizing a minimum number of carrier frequency assignments to the transmitters situated at terminal and repeater stations of a communications network, while avoiding mutual interference between adjacent links of said network, said method comprising the steps of allocating at least three different carriers individually to each of the single transmitters at one terminal station and at two stations nearest and next in order in said network, tuning each of two radio receivers at each repeater station so that reception may be had from either of two stations directlyassociated therewith, and connecting each repeater station transmitter exclusively to a selected one of the receivers of the same repeater station, thereby to repeat the transmission of terminal station, the

- station,

peater stations ltions, the combination of a receiver and peater station, each of ,carrier frequency assignments of one of three assigned the transmitter at I and switching means ,sponsive. to an incoming signal to cause each repeater station transmitter to be connected to the ,frequency B is assigned toa repeater station with in the transmission range of said one terminal station, frequency 0 is assigned to the next repeaterstation in the direction of the other terminal station and frequency assignments A, B and-C are: applied progressively to other repeater stations situated in the direction of said other transmitter frequency assignment of said other terminal station being different from that of the two repeater stations nearest thereto, means for causing the transmission range of each of said stations to be ineffective beyond twice, the distance to each related a pair of receivers at each repeater station individually tuned to one and the other of the two said frequencies which are exclusive of the transmitter frequency at the same repeater station, and means automatically operative for modulating each repeater station transmitter under the exclusive control of incoming signals accepted by whichever one of the two associated receivers produces the first response after a nosignalling period.-

3. In a radio relay system comprising two terminal stations and a plurality of intervening refor interlinking a one-way channel in either direction between said terminal staa transstation, the combination transmitter at each resaid transmitters having mitter at each terminal of. two receivers and a predetermined frequencies assigned progressively to said stations along said system from one to the other terminal station, means to cause the transmission range of said stations to be ineffective beyond twice the distance ,the receivers at each repeater station being indi- ;vidually tuned to three frequencies exclusive requency at the same repeater station, the re- ,ceiver at each to each related station,

one and the other of two of said of the transmitter terminal station being responsive three frequencies other than that that terminal station, at each repeater station reto one of said receiver which accepts said incoming signal to relay the same, and further switching means at each repeater station to isolate said transmitter from control by the other receiver thereat.

4. In a radio relay network comprising two terminal stations and a plurality of interveningrepeater stations, transmitting and receiving apparatus at each station, each transmitting apparatus having its carrier frequency assignment selected from three predetermined frequencies assigned progressively to stations from one terminal station to the other, means for causing the transmission range of each of said transmitters to be ineffective beyond the distance between alternate related stations to avoid feedback interference with other stations of said network hav- 7 ing the same carrier frequency assignment, the

' receivers at each repeater station being individually tuned to one and the other of the two of said three frequencies which are exclusive of the transmitter frequency at the same repeater station, and means for modulating the outgoing carrier wave ofeach repeater station transmitter by incoming signals of a message to which the receiving apparatus at that station first responds after a no-signalling period, said signals being borne by a carrier wave of one of said three predetermined frequencies, and lock-out means to isolate said transmitting apparatus from the mitter frequency assignment of each station being different from that of the two stations nearest thereto and no receiver being within twice the transmission range of any of said transmitters operating on a frequency to which the receiver is responsive, the receivers at each repeater station being individually tuned to one and. the other of the two of said three frequencies which are exclusive of the transmitter frequency at the same repeater station.

6. A radio relay system including a chain of repeater stations, each of said stations having two receivers and a transmitter, each transmitter being tuned to one of three predetermined fref quencies to which one receiver at each adjacent station is responsive, said three frequencies being assigned progressively to the stations along said chain, the receivers at each repeater station being individually tuned to one and the other of the two said frequencies which are exclusive of the transmitter frequency at the same repeater station, and a terminal station at each end of the system, each of said terminal stations including a transmitter and a receiver tuned to co-operate "with a receiver and transmitter of the adjacent repeater station, no receiver being within the transmission range of a transmitter having the same frequency assignment and located beyond twice the distance to each related station.

7. A radio relay system including a plurality of repeater stations interposed between two termi-.

nal stations, each of said repeater stations having elements comprising two receivers and a transmitter, the carrier frequency assignments of each of which element is one of three predetermined frequencies assigned in regular progression to the elements of repeater stations alongsaid system from one to the other terminal station, the transmitter frequency assignment of each station being different from that of the two stations nearest thereto, means for causing the transmission range of each of said stations to be ineffective beyond twice the distance to each related station, signal responsive means at each repeater station to apply operating potentials to the transmitter, and means to couple the modulating circuit of said transmitter exclusively to the one of the associated receivers at said station which first responds to signals after the lapse of a non-signalling period, and means for locking out the control of said transmitter by the other of the associated receivers.

8. A radio relay system comprising a chain of relay stations, each of said stations having two receivers and a transmitter, each transmitter being tuned to one of three predetermined frequencies to which one receiver at each adjacent station is responsive, means for causing the transmission range of each of said stations to be ineffective beyond twice the distance to each related station, the receivers at each repeater station individually tuned to one and the other of the two said frequencies which are exclusive of the transmitter frequency at the same repeater station, remote control apparatus in operative association with the receivers and transmitter at each repeater station, said apparatus including switching means responsive to incoming signals to establish exclusive control of the transmitter by whichever one of the two associated receivers first responds to said incoming signals, and means operative during such response to prevent the reversal of said switching means upon subsequent response of the other receiver to other incoming signals.

HAROLD H. BEVERAGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS I Date Number Name 1,624,966 Morris Apr, 19,1927 1,927,827 Goldsmith Sept. 26, 1933 2,106,806 Latimer et a1 Feb. 1,1938 2,146,301 Knotts et a1. Feb. 7, 1939 2,155,821 Goldsmith Apr. 25, 1939 2,250,950 Goldsmith July 29, 1941 2,292,222 Haigis Aug. 4, 1942