US1884536A - Radio signaling - Google Patents

Description

Oct. 25, 1932.

W. R. BLAIR ET AL RAD IO S IGNALING Filed Nov. 24, 1928 2 SheetsSheet OOOOOOOQOQDDDDDDDDDDD wwwwadcccccccooooooooocoo Try/7501256)" Z77ve77%ra @Zaulu Oct. 25, 1932.

w n 6 .w 7 EA 6 "mg I oooaooooaoooooo oooooaoaooooboon 2 Km r0 0 ODJDANDODODDDDD M q no 0 CGCCOCCOGCCCCOC mwsmzz ier 2 2 Fans/ni er Patented Get. 25, 1932 UNITED STATES PATENT OFFlCE WILLIAM.R. BLAIR AND LOUIS COHEN, OF WASHINGTON, DISTRICT OF COLUMBIA RADIO SIGNALING Application filed November 24, 1928. Serial No. 321,688.

(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

.5 This invention relates to the art of radio signaling and more particularly to improved methods in the transmission of radio signals.

One of the objects of this invention is the elimination of harmonic frequencies in the transmission of radio signals.

Another object is the reduction to a minimum of the width of the frequency band occupied bya transmitter in the emission of signals.

A further object is to provide means for the simultaneous transmission of several radio signals of different frequencies from a single antenna.

In the production of electrical oscillations by the three electrode vacuum tube method,

and this is the method most generally used in practice at the present time, it is very difficult to produce oscillations of a pure sine wave form of a single frequency. The oscillations produced are generally of a distorted wave form, that is the oscillations comprise a fundamental frequency and harmonic frequencies. Also the fact that an antenna, which is an oscillator of an infinite number of degrees of freedom and can therefore respond resonantly to many frequencies, forms part of the transmitting oscillating system, helps to give emphasis to the harmonics in the radiation from the antenna. The useful signal transmission requires, of course, oscillations of one frequency only, and the transmission of the harmonic frequencies is an unnecessary cause of interferences, not serving any useful purpose whatsoever; it does not contribute in any way to the efficiency of transmission.

The presence of harmonics in the transmission of signals is very objectionable because of interference caused on other frequencies besides the one on which the signal is transmit- ,45 ted. Many attempts were made to remedy or at least to mitigate this evil, such as the use of amaster oscillator, filter circuits, and other devices, but it is found in practice that even with the aid of these improvements the har-- monies are not completely eliminated, and in some methods the apparatus required is too complicated for general use.

This invention contemplates a novel circuit system whereby the oscillations of the transmitter are impressed on'the antenna through the intermediary of a wave conductor, that is a conductor of distributed inductance and capacity on which a wave development is effected, and suitably adjusted in relation to the fundamental frequency of the transmit- 6Q ter oscillations. By this means the oscillations of the fundamental frequency only are impressed on the antenna, or a wire as the case may be, and the radiation is free from harmonics. This method also offers a convenient means for the simultaneous transmission of several signals of difierent frequencies from a single antenna or over a single Wire. The method is best understood by referring to the accompanying drawings which form part of this specification in which Figure 1 shows diagrammatically an embodiment of the invention in which the trans- ,mitter is connected to a wave conductor and a tuned antenna coupled to the wave conductor. i

Figure 2 shows a modification of the invention in which an untuned antenna is used.

Figure 3 is similar to Figure 2' except that the wave conductor is grounded. 0 Figure 4 is an embodiment of the invention showing the simultaneous transmission of two signals of different frequencies from a single antenna.

Figure 5 shows an embodiment oftheinvention illustrated in Figure 2 in its application to the transmission of signals over wires.

Having particular reference to the drawings in which similar numbers designate the same parts in all of the drawings, in Figure 1 1 the transmitter 1, which is preferably of the vacuum tube type, is associated with an oscillatory circuit 2, 3. The oscillatory circuit is connected at t to the metal shield 6, 6 which is placed in close proximity to the wave coilv 5, 5; The wave coil 5, 5 and metal shield 6, 6 as well as the coupling coil 7 are all shown in this figure in cross section. The wave coil 5, 5 Which is preferably in the form of a solenoidal coil, though it may be any other form 1 9 of coil, together with the metal shield 6, 6 forms a wave conductor that is one of distributed inductance and capacity and of sutlicient length in relation to the wave length of the transmitted oscillations to assure a wave development thereon. An adjustment of the wave conductor is effected by varying the distance separation of the metal shield 6, 6 from the wave coil 5, '5. The metal shield 6, 6 may be in the form of semi-cylinders partially surrounding the wave conductor or preferably flat plates. A coupling coil 7 is placed within the wave coil 5, and this coupling coil 7 is connected in series in the antenna which comprises also in series a variable condenser 9, a loading coil 10 and ground 11. By the proper tuning of the antenna and suitably adjusting the wave conductor, that is the distance separation of the metal shields from the wave coil, all in relation to the frequency of the transmitter, an adjustment is effected whereby considerable current is transmitted to the antenna, and only of a single frequency that of the fundamental frequency of the transmitter. In actual test it was found that with this arrangement the harmonics, though very pronounced in the transmitter, could not be detected in the antenna even by coupling a wave meter close to the antenna.

- Figure 2 shows an embodiment of the in vention by which the same results are accomplished with an untuned antenna. Here the point 4 of the oscillating circuit 2, 3 is connected to one end 13 of the wave coil 5, 5 and the antenna 8 is connected to the metal shield 6, 6 at point 12. The only adjustment'requiredjn this arrangement is the varying of the distance separation of the metal shield 6, '6 from the wave coil 5,5. With this ar- -mgement it is also found that the oscillations in the antenna are completely free from harmonics, the oscillations in the antenna are only those of the fundamental frequency of the transmitter.

The arrangement shown in Figure 3 differs from Fi ure 2 only in one detail and that is that t e other end of the wave coil is grounded. Results similar to those obtained b the arrangement shown in Figure 2 are a obtained with the arrangement shown in Figure 3.

The systems shown in both Figure 2 or 3 have a great advantage in that the antenna is nn tuned, simplifying considerably the adgstments required and also affording therea convenient means for multiplex transmission, that is operating several transmitters of different frequencies on the same antenna. This is shown in Figure 4 in which,

" for the purpose of illustration, only two transmitters are shown associated with one antenna. The oscillating circuit 15 associated with transmitter 14 is connected first at 18, and then at 19 to the wave coil 16, 16

and its metal shield 17, 17'is connected at 20 to the antenna 21. Similarly the oscillating circuit 23 associated with transmitter 22 is connected to the latter at 24 and then at 25 to the wave coil 26, 26 and its metal shield 27, 27 is connected to the same antenna 21 as at 28. The wave conductors 16, 16; 17 17 and 26, 26; 27, 27 are each separately ad justed in relation to the frequencies of the respective transmitter associated therewith. Additional transmitters associated with properly adjusted wave conductors could be connected on to the same antenna, thus affording a means for the simultaneous transmission of several signals of different frequencies from a single antenna.

Itis obvious that this system is also applicable for the transmission of signals over wires as the connecting of the transmitting station with a receiving station by means of a wire amounts simply to the extension of the antenna to reach from one station to the other. Since in this arrangement the tuning is altogether independent of the antenna, it is obvious that the antenna may be lengthened to any degree desired and thus obtain the desired condition of wire transmission. This is shown in Figure 5 which differs from that shown in Figure 2 only in that in place of the transmitting antenna, the transmitting circuit is connected to a wire 29 which extends all the way to a receiving station 30.

We claim:

1. In a system for the transmission of radio signals comprising an oscillation energy source associated with an oscillating circuit, awave conductor and an antenna, said wave conductor comprising a wave coil and a metal shield in proximity thereto, said oscillatin circuit being connected at one point to said metal shield, said wave coil being open at both ends, a coupling coil which is coupled to said wave coil being connected in series in said antenna.

2. In a system for the transmission of radio signals comprising an oscillation energy source associated with an oscillating circuit, a wave conductor and an antenna, said wave conductor comprising a wave coil and a metal shield in proximity thereto, said oscillating circuit being connected at one point to said metal shield, said wave coil being open at both ends, a coupling coil which is coupled to said wave coil being connected in series in said antenna, said an tenna comprising in its circuit a variable condenser and loading coil by which the antenna circuit is adapted to be tuned for the frequency of the oscillations of the transmitter.

3. In a system for the transmission of radio signals comprising an oscillation energy source associated with the oscillating circuit, a wave conductor and antenna, said wave conductor comprising a wave co'il'and a metal shield in proximity thereto, said oscillating circuit being connected at one point to said metal shield a coupling coil which is coupled to said Wave coil being connected in series in said antenna; the frequency of the oscillation source being adjusted for res onance to the natural period of the said wave coil.

4. In a system for the transmission of radio signals comprising an oscillation energy source associated with the oscillating tures.

WILLIAM R. BLAIR. LOUIS COHEN.

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