US1868795A

US1868795A - Antenna

Info

Publication number: US1868795A
Application number: US161769A
Authority: US
Inventors: Clarence W Hansell
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1927-01-18
Filing date: 1927-01-18
Publication date: 1932-07-26
Anticipated expiration: 1949-07-26
Also published as: DE491416C; NL23498C

Description

July 26, 1932. w, N ELL 1,868,795

ANTENNA Filed Jan. 18. 1,927

INVENTOR C.W HANSELL TORNEY U E STATES PATENT OFFICE CLARENCE W. HANSELL, F ROCKY POINT, NEW YORK, ASSIGNOR TORADIO CORPORA- Patented July 26, 1932 TION' OF AMERICA, A CORPORATION OF DELAWARE ANTENNA Application filed January 18, 1927.1 Seria1 no. 161,769.

This invention relates to antenna arrangements, and more particularly to short wave antennae lead-in wires, and a method and means for coupling them to the antenna.

In arranging for the radiation of high frequency energy it is frequently tound'that the length of lead-in from the antenna is considerably greater than a wave length, and that in this lead-in standing waves are set up Which cause great losses. In fact, I find that the flow of large quantities of'wattless' current over even a straight conductor may sometimes create a. potential gradient of hundreds of volts per inch, inasmuch as the high fre! quency makes for high reactance.

Another disadvantage of an ordinary lead in system is its tendency to. radiate energy which may be "differently directed and out of phase with that radiated by the antenna It is an object of my invention to overcome these difiiculties, and to providea lead-in which will obviate the possibility of standing waves and high losses, and which will not effect appreciable radiation.

I accomplish these objects by providing,

instead of a simple-lead-in or a haphazardly arranged pair of lead-in wires, a pair'of lead-f in wires'so coupled to the antenna that they possess the characteristics of an infinite transmission line. I 'f The specification is accompanied by a drawingin which Fig. 1 is a wiring diagram of an arrangement according to my invention; Fig. 2 is a schematic layout, inperspective', of an embodimentot my invention; and

Fig. 3 shows an antenna of harmonic length.

Certain characteristics of a transm ssion line which may be'demonstrated' mathematia cally I shall more simply illustrate by reference to asupposititious transmission line extending to infinity. Such a transmission line of infinite length wouldobviously be characterized by a total absence of reflections and standing waves, for the reason that the impressed'energy wouldnever reach the end of the line to be reflected, and standing waves usually are caused by a reflected wave com.-

bining with the'original wave. 7 r

If a source of current were connected to such a fictltious transmissionjllne there would be no apparent difi'erence betweenthe conse quent eitect and that which would be caused by connecting a resistive load to the same source, would be dissipated in it, for such energy could not conceivably reach the end ofthe line. As in the case of a resistiveload, there would he a definite limit to the rate of flow of energy, because the rapidity of energy absorption would dependupon'theflow velocity in the line,and this in turn depends, for both The energy supplied .to the "line a finite and aninfiniteline, upon the relative inductive. and capacitive characteristics or the line, 'asdetrrmined by'the physical dimensions and spacing of the conductors composing it. o a

' This equivalent resistance or apparent im'e pedanceof a transmission line of specified transverse dimensions when supposedo finfi'- nite length is termed the characteristic ime pedance of the'line. In the case ottwo A wires,approximately one foot ap art,'thecha'r-f acteristic impedanceis about 600ohms.

Now suppose that at a finite distance from the beginning of such a fictitious infinite transmission line a. break is'made; Then,

because a finite subtracted from an'infinite leaves an infinite, the line extending from the break to infinity would stillbe an infinite transmissionline, and would'stillhave the same characteristic impedance; as before. The finite transmlss on lme extending to the break typlfiesa transmission line in use,and

it, across the remote terminals of this finite tI'fiIlSllllSSIOIlllIlB, an m'pedance is connected equal to the characteristic impedance of the infinite transmission line, I then the :finite transmission line will possess all of the tide sirable, features already attributed tofthe fictitious line, namely, no refie ctions and standing waves, substantially unity power factor, and substantially no wattless current losses. I I

Referring to the drawing, the. short wave antenna is represented by the numeral 2, and

to it there are coupled the conductors 4,

which, byway of the blocking condensers 6,

are coupled to the output inductance 8 ofthe transmitter 10. According to my invention the points A and B are so spaced that the impedance therebetween is equal to the characteristic impedance of the conductors 4:, considered as a transmission line.

One simple procedure for determining when the proper location of the points A and B has been obtained utilizes a plurality of ammeters inserted along the lead-in wires, which are made to read alike. To avoid the possibility of locating the ammeters symmetrically with respect to a standing wave, at least three ammeters should be used, and these should be spaced unequally. In Fig. l the ammeters are 22, 24, and 26, and the space between 22 and 24: is different from that between 24 and 26.

Referring now to Fig. 2, the antenna is the conductor 2, and it is supported upon the masts l2 and insulated therefrom by the insulators 14;. The conductors l, as before, are coupled to the antenna at the properly spaced points A and B, and these conductors are guided to the building- 16, in which the transmitter is housed. The point of bend of the transmission line l may be supported by a wire 18 and insulators 20.

The antenna need not necessarily be one half a wave in length. It is desirable that the coupling points be symmetrically located with respect to a potential node and a current antinode. Thus in Fig. 3 a. linear oscillator one and one half waves in length is illustrated. In both Fig. 1 and Fig. 3 the solid curve indicates potential, while the dotted curve indicates current.

The lead-in wires do not elfect appreciable radiation because they tend to neutralize one another, and also because they extend in the direction of their wave propagation, instead of transversely thereof.

It is prefectly feasible that the antenna be horizontal, oblique, or vertical, but it is well in the case of a vertical or oblique antenna to increase the elevation in order that the capacitance from each half of the antenna to ground may not be appreciably unbalanced.

What I claim is:

1. In combination, means to radiate high frequency energy including a simple linear oscillator, and a plurality of lead-in wires directly coupled thereto at points so spaced that the external impedance across which the lead-in wires are connected is equal to the characteristic impedance of the lead-in wires.

2. An antenna arrangement for the radiation of very short waves comprising a simple linear oscillator an odd number of half wave lengths long, and lead-in wires directly symmetrically coupled thereto at points so spaced that the impedance therebetween equals the characteristic impedance of the lead-in wires.

3. An arrangement for the radiation of short waves comprising a transmitter havingan output circuit, a short wave antenna,

comprising a linear radiator an odd num-' ber of half wave lengths long, blocking condensers, and lead-in wires coupled to the output circuit through said blocking condensers, and directly coupled to the linear radiator of the antenna at points so spaced that the external impedance across which the lead-in wires are connected is equal to the characteristic impedance of the lead-in wires.

a". An antenna arrangement for the radiation of very short waves comprising a straight wire oscillator an odd number of half wave lengths long, and lead-in wires directly symmetrically coupled thereto at points so spaced that the impedance of the portion of straight wire of the oscillator therebetween equals the characteristic impedance of the lead-111 wires.

5. The method of adjusting the coupling of a transmission line to an antenna so that there will be no reflection of energy from the antenna end of the line back into the line which includes varying the coupling at the antenna end of the line until a plurality of indicating devices, responsive to high frequency currents, placed in the line, and spaced other than a half wave length or a whole multiple thereof apart, read alike.

(5. in a high frequency communication system employing lead-in wires coupled to an antenna, the method of coupling the lead-in Wires to the antenna which includes placing a plurality of indicating devices, responsive to high frequency currents, in the lead-in wires unequal distances apart the distances taken being other than one-l1alf wave length or a whole multiple thereof, and varyin the coupling of the lead-in wires with the antenna until the indicating devices, responsive to high frequency currents, read alike.

7 in a high frequency communication system employing load-in wires directly coupled to a short wave antenna, the method of locating the antenna coupling points for the leadin wires which includes placing a plurality of indicating devices, responsive to high frequency currents, in the lead-in wires unequal distances apart, the distances taken being other than onehalf wave length or a Whole multiple thereof, and varying the coupling points on the antenna until the indicating devices read alike.

8. In a system for transmitting intelligence from one geographically situated point to another by means of propagated electromagnetic wave energy derived from the flow of high frequency undulatory electrical currents operated upon in accordance with the intelligence to be transmitted, the combination of a simple linear oscillator, and, a plurality of lead-in wires directly coupled thereto at points so spaced that the external impedance across which the lead-in wires are connected is equal to the characteristic impedance of the lead-in wires.

9. In a system for transmitting intelligence from one geographically situated point to another by means of propagated electromagnetic wave energy derived from the flow of high frequency undulatory electrical currents operated upon in accordance with the intelligence to be'transmitted, the combination of a simple linear oscillatoronehalf wave length long, and, a plurality of lead-in wires directly coupled thereto at. points so spaced thatthe external impedance across which the lead-in wires are connected is equal to the characteristic impedance of the lead-in wires. J

10. In combination, means to radiate high 4 frequency energy including a simple linear oscillator substantially one-halfwave length long, and a plurality of lead-in wires directly coupled thereto at points so spaced that the external impedance across which'the lead-in wires are connected is equal to the characteristic impedance of the lead-in wires.

c w. HANSELL.