US2154923A - Signaling system - Google Patents

Description

April 18, 1939.

J.V C. WALTER SIGNALING SYSTEM AFiled oct. 3, 1956 3 Sheets-Sheet l April 18, 1939.` J. c. WALTER i SIGNALING SYSTEM Filed Oct. 3, 1936 3 Sheets-Sheet 2 IN V EN TOR.

ATTORNEY April 18, 1939.` J. C; WALTER 2,154,923

SIGNALING SYSTEM Filed Oct. 5, 1956-- 3 Sheets-Sheet 5 lil-:1.13-5

TRANSMITTER RECEIVER RECEIVER AREA AREA COVERED BY COVERED BY f=555o nos. Ef=173nu KCS.

17300 KCS' HEAvlSmE (Ef) REFLECTING 355m KCS. /Y n LAYER TRANSMITTER R RECElVER Q EARTH 77 IN V EN TOR. on C wolf/bev A TTORNEY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE SIGNALIN G SYSTEM ration of Delaware Application October 3,

2 Claims.

This invention pertains in general to signaling systems, and specifically relates to a multiple signaling system.

The present invention deals with the transmission of programs to several remote points. For example, it may be desired to transmit one or more programs to several distribution points, such as wired radio networks located in cities remotely situated from each other. When it is desired to transmit a signal to two such distant points by high frequency waves, the selection of the most effective frequency for each leg of the circuit must be made with respect to conditions controlled by the Kenelly-Heaviside effect. If the receiving points are considerably displaced from one another and from the transmitter, the selection of an eflicient frequency for simultaneous transmission to both receiving points becomes difcult and reaches the point of impossibility when the distances become remote from each other, as, for example, when the points of reception for daylight transmission are located approximately 1000 miles and 3000 miles from the transmission point. With respect to these particular distances, it has been found that 8650 kilocycles is the most reliable frequency for the 1000 mile transmission length, while a frequency in the neighborhood of 17,000 to 18,000 kilocycles is most eective for the 3000 mile transmission length. While using the 8650 kilocycles on the 1000 mile length, it is found that the signal is heard With marked intensity at points from 400 to 1200 miles from the transmitter, but beyond 1200 miles severe attenuation sets in. At the 3000 mile point, the signal is practically nonexistent. Although specific distances are used by way of illustration, similar conditions prevail for other correlated conditions.

A frequency of 17,300 kilocycles appears to be efficient for transmission to a reception point between 1800 and Li000 miles. However, the skip effect for this frequency makes it uneifective for transmission to the receiving point located 1000 miles from the point of transmission. The use of intermediate frequencies is also fraught with difficulty due to severe fading resulting from only slight changes in the Kenelly- Heaviside layer.

rlhe principal object of the present invention consists in providing a multiple transmission system for transmitting programs to plural reception points substantially displaced from one another.

A further object of the invention comprises providing a transmission system for simultane- 1936, Serial No. 103,921

(Cl. Z50-6) ously transmitting a program to a plurality of remote points by commonly developed frequencies of different orders.

A further object of the invention consists in the method of transmitting with respect to the 5 Kenelly-Heaviside layer for simultaneously propagating waves by reflection from a common transmission point to a plurality of remotely situated receiving points.

These and other objects are accomplished by 10 the following, reference being had to the accompanying drawings in which like reference numerals designate corresponding parts and in which:

Fig. l is a schematic representation of a pre- 15 ferred system of propagation in accordance with the principles of the invention;

Fig. 2 is a diagrammatic representation of circuits employed in the system of Fig. 1; 20

Fig. 3 is a graphical representation of transmission conditions in accordance with the invention; and

Fig. 4 is another graphical representation of transmission conditions in accordance with the invention. 25

Referring to the drawings in detail, and particularly to Fig. l, a program source l is connected with a common transmission unit 2 which controls the transmitter 3, designated as transmission unit A, and a transmitter 5, designated as transmission unit B. The program source I comprises one or more studios and audio amplication equipment for producing one or more channels of audio frequency program modulation energy. The program energy from source I is conveyed to the common transmission unit 2.

The common transmission unit 2 is connected with a master oscillator 2a for producing a base frequency and a harmonic generator 2b to develop a fundamental high frequency f from which is derived a second harmonic frequency 2f, both modulated by the program energy to produce carrier and side band modulation frequencies. The master oscillator base frequency 2q may be of any conventional type of crystal controlled electron tube oscillator, and the harmonic generator 2b may be of a conventional type for producing harmonics. Reference is made to United States Patents Nos. 1,912,322 and 1,766,047. When it is desired to transmit more than one program, the several programs can be individually utilized to modulate intermediate carrier frequencies, which carrier frequencies are utilized to modulate the frequencies f and 2f and appear in connection therewith as modulation ll-x side bands. The carrier frequencies f and 2f are conveyed to the transmitter units 3 and 4 which respectively comprise power'ampliers and associated circuits for transmitting the respective frequencies.

Fig. 2 illustrates, in more detail, part of the circuits utilized in the transmitting units shown in Fig. 1. Referring to Fig. 2, the common transmission unit 2 includes a push-pull amplifier having electron tubes I5 and I6 operating through a tuned circuit including inductance I'l and capacitor I8. Capacitive couplings are provided from the unit 2 to the unit 3 and to the unit 4.

The unit 3 includes an input tuned circuit comprising inductance I9 and capacitor 20 serving to energize the input electrodes of power amplifying electron tubes 2I and 22. The anode or output circuit of tubes 2| and 22 includes an output resonance circuit having the inductance 23 and capacitor 24. The inductance 23 is coupled with inductances 26 and 21 which operate through capacitors 28 and 29 to energize an antenna system including the array 30 and ground 3I. The antenna system S0-3l, in conjunction with the unit 3, as energized by unit 2, transmits the modulated carrier frequency f. Circuit components not shown in the unit 3 of Fig. 2 are of conventional form.

Unit 4 comprises circuit components corresponding with related parts of the unit 3 with the exception that the parameters of these circuit components are adjusted so that the circuit as a whole, in cooperation with antenna system 3Ilb-3Ib, transmits the modulated carrier energy at frequency 2f. For purposes of illustration, the frequencies f and 2f may be 8650 kilocycles and 17,300 kilocycles, respectively.

Referring again to Fig. l, the waves propagated from the antenna system of unit 3 are received by equipment 5, designated as receiver A. Equipment 5 receives the high frequency short wave signals from unit 3 and converts such signals into modulation energy suitable for controlling a local transmitter 6. The local transmitter 6 comprises a local master oscillator for producing a base frequency which may have an harmonic relationship with, and be controlled by, the frequency of the master oscillator of unit 2. This may be accomplished by a wire line connecting the latter oscillator with the local oscillator. Such wire line need not be of the high quality required to transmit a band of frequencies, inasmuch as it is required to transmit the base frequency only. It is preferable, however, in View of the long distance between the several transmitters to use a component of the space radio from receivers A and B to control respectively the frequencies of the local master oscillators. This may be accomplished in a known manner by frequency dividers. The purpose of this controlled or synchronized relationship is to insure that all of the transmission frequencies used in the system are kept directly or harmonically in step. The transmitter 6 also includes means in the form of a sub-harmonic polyphase generator for developing polyphase carrier frequency within a frequency range suitable for impression on a power transmission network such as within the range of 26-78 kilocycles. The master oscillator and harmonic polyphase generator may be of conventional form for producing the results desired. Preferably, the master oscillator is of a crystal controlled, electron tube type with the crystal ground to the same frequency as the frequency of the oscillator 2a, or a harmonic thereof. Reference is made to United States Patents Nos. 1,622,135; 1,730,412; 1,820,898 and 1,823,851. The program modulation energy is utilized to modulate such carrier frequency energy which is then placed upon the transmission medium I designated as transmission network A. The transmission network A comprises a power network such as the commercial alternating current distribution system of a municipality and includes power generators, voltage control equipment, and distribution lines to the consumers circuits which include both power and wired radio receiving equipment.

Equipment 5B, designated as receiver B, corresponds to equipment 5, designated as receiver A, except that the receiver B is adjusted for reception of frequency 2f after being transmitted from equipment 4, designated as transmission unit B.

The receiver B operates to receive the program energy transmitted from unit 4, as represented by the high frequency short wave signals comprising frequency 2. This received energy is converted into the modulation energy which controls the equipment 6B and equipment 'IB which correspond in nature and function with equipments t and 7, respectively, except that the two systems connected respectively with receiver A and receiver B are geographically displaced to a considerable extent. For example, the receiver A may be situated 1000 miles from the transmission point, and receiver B may be situated 3000 miles from the transmission point.

Fig. 3 illustrates the effective transmission eld areas in which receiver A and receiver B are located with respect to the transmitter. Fig. 4 illustrates the reiected propagation of waves to receivers A and B by virtue of the different frequencies. is reflected by the Kenelly-Heaviside layer to the receiver A, and that the frequency 2 ,f is reflected by the Kenelly-Heaviside layer to the receiver B, thereby permitting both receivers to receive the same program by frequencies harmonically related to each other and to a base frequency.

Although a specific embodiment of the system has been disclosed, it will be obvious that many changes and modifications can be made without departing from the intended scope of the inu vention. Therefore, no limitations are intended except as pointed out in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A signaling system comprising, a source of program modulation energy, a transmission source associated with said program source for producing from a base frequency and transmitting through space a plurality of different carrier frequencies all harmonically related to each other and to said base frequency and all modulated by said program modulation energy, receiving stations positioned at points geographically displaced with respect to said transmission source, said receivers being individually responsive only to a particular one of said carrier frequencies, a retransmission System connected with each of said receivers, said retransmission systems each including means for generating a local master frequency and deriving therefrom a sub-harmonically related retransmission frequency, said local master frequency being harmonically related to said base frequency, means including the output of said receivers for modulating said harmonically related retransmission It will be seen that the frequency f frequencies, and means for transmitting the frequencies thus modulated.

2. A signaling system comprising, a source of program modulation energy, a transmission source associated with said program source for producing from a base frequency and transmitting through space a plurality of different carrier frequencies all harmonically related to each other and to said base frequency and all modulated by said program modulation energy, receiving stations positioned at points geographically displaced with respect to said transmission source, said receivers being individually responsive only to a particular one of said carrier fre- 15 quencies, a retransmission system connected with each of said receivers, said retransmission systems each including means fo-r generating a local master frequency and deriving therefrom a sub-harmonically related retransmission frequency, said local master frequency being harmonically related to said base frequency, a Wired radio network including a power distribution system connected with each of said retransmission systems, means including the output of said receivers for modulating said harmonically related retransmission frequencies, and means for transmitting the frequencies thus modulated over said Wired radio networks.

JOHN C. WALTER.

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