US2175252A

US2175252A - Short wave antenna

Info

Publication number: US2175252A
Application number: US147817A
Authority: US
Inventors: Philip S Carter
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1937-06-12
Filing date: 1937-06-12
Publication date: 1939-10-10
Anticipated expiration: 1956-10-10
Also published as: GB515795A

Description

' .Oct. 10,1939, I s. CARTER v SHORT WAVE ANTENNA Filed June 12, 1937 l I I I 1 nvsuur/o/v I m FREQUENCY v APPARA rus I INVENTOR I PHIL/P 5.04pm? I BY v v ATTORNEY r Patented a. 10, 1939 2,175,252

UNITED STATES PATENT OFFICE 2.1mm snoa'r wave ANTENNA Philip 8. Carter, Port .Ieilerson, N. Y., assignmto Radio Corporation of America, a corporation of Delaware Application June 12, 1937, Serial No. 147,817

6 Galina. (Cl. 250-33) The present invention relates to short wave of the antennas constructed in accordance with antennas, and has for its primary object to prothe principles of the invention.

vide a short wave antenna which will present Referring to Fig. 1, there is shown an hournegligible reactance at its terminals over a wide glass type of antenna comprising two conducting frequency range such is may be used in telesurfaces of revolution inthe form of hollow-cones 5 vision transmission or reception. I and 2 symmetrically arranged about a vertical Where a wide band of frequencies is used, such axis, the apices being placed adjacent each other. as in the transmission of television programs, it The cones are excited at their adjacent apices is desired that the antenna act, in an ideal case, by means of a concentric transmission line TL as a pure resistance of constant magnitude over which extends from a remotely located trans- 10 a wide range of frequencies, in order to prevent mitter 3, usually flve or more wavelengths away wave reflections (i. e., standing waves) along from the antenna, .the inner conductor being the feeder, inasmuch as reflections cause variaconnected to the apex of one of the cones, let us tions in the input impedance of the transmission say the upper cone l, as shown, while the outer line at the transmitter and increased losses in the conductor is connected to the other cone 2. transmission line. Such effects are especially The energy radiation'pattem obtained by the deleterious when the length of the transmission system of Fig. 1 is indicated in dotted lines by P, line feeder to the antenna is relatively long with which it will be noted is similar to that of a respect to the wavelength, such as flve wavehalf wave dipole, It will be observed that there lengths and greater. is obtained maximum radiation at right angles 20 It has been observedthat it is extremely diflito the axis of the cone; the pattern being circucult, if not impossible to attain the ideal case in at right angles to the drawing, and a figure 8 mentioned above, where an antenna will act as in the plane of the drawing. 9. pure resistance of constant magnitude over a Fig. 2 illustrates a modification of the antenna wide range of frequencies. Consequently, in conof Fig. 1 and employs a single hollow cone 4 dis- 25 structing an antenna for the purpose hereinabove posed above a reflecting surface which may be the described, it is essential to bear in mind that in conducting roof of a building. This surface may most cases the introduction of a reactance combe at ground potential. Similarly, as in Fig. 1, ponent of an impedance (such as an antenna) a concentric transmission line TL may be emloading a line, sets up considerably more reflecplayed to energize the cone, the inner conductor 30 tion in the line than a moderate variation in the connecting to the apex of the cone while the resistance component, outer conductor is connected to the reflecting The present invention provides a highly desirsurface. able type of short wave antenna for use over a Fig. 3 illustrates an arrangement which was wide frequency range, which presents at its teractually used in practice with the dimensions 35 minals an impedance appearing almost asa pure indicated on the drawing. The length of the resistance, the phase angle of the impedance becone indicated is the mean wavelength of the ing very small. Putting it another way, the range of wavelengths over which the antenna is antenna of the invention introduces practically designed to operate. It will here be noted that no reactive component with variation in frethe transmission line is a two-wire line. instead 40 quency. of..the coaxial line shown in Fig. 1. The two In brief, the antenna of the invention com.- cones l and 2 are maintained in position with reprises one or more conducting surfaces of revospect to each other by fo r insulating. rods 5 lution in the form of cones, preferably energized fastened to the edges of the cones, as shown.

at their apices. In accordance wtih one embodi- With such an antenna, the impedance of the an- 45 ment of the invention, there are employed two tenna was an almost pure resistance for a range conducting cones symmetrically arranged along of wavelengths varying from 1.36 meters up to the same axis, apex adjacent to apex, in such 1.55 meters, the phase angle of the impedance manner as to give the appearance of an hourin all cases being less than 4 or 5. The impedglass. In accordance with another embodiment, ance characteristic was determined from meas- 50 the antenna comprises a single cone disposed urements made along the transmission line feedabove a reflecting surface or ground. 1 ing theantennai'a The resistance varied linearly A more detailed description of the invention from a "value 'of 75"ohms at 1.55 ineters to 104 follows in conjunction with a drawing, wherein ohms at 1.36 meters. It should be noted that Figs. 1 and 2 illustrate two diflerent embodiments although there was a moderate variation in re- 55 sistance, there was only negligible reactance over the range of frequencies employed.

Although the antenna of the system has been shown arranged vertically, it should be distinctly 5 understood that the cones can be disposed at any angle to the vertical and that the transmission line may be any desired type and may be connected to the cones at points other than the apices for purposes of impedance matching. It 10 will also be obvious that the antenna may be used both for transmission or reception. The cones may have other angles and may, in some cases, be solid.

What is claimed is:

1 1. In combination, a short wave antenna comcones symmetrically located with respect to a common axis passing through their apices, said spines '0 being adjacent one another, a two conductor transmission line having the length relatively long with respect to the operating wave length directly connected to said cones, a translating apparatus connected to said transmission line,

a the length and diameter of each of said surfaces of revolution being such that the impedance of said antenna is substantially a pure resistance of constant magnitude over a wide range of frequencies.

3. The combination with a short wave antenna comprising a surface of revolution in the form of a cone, of translating apparatus, and a line connecting said translating apparatus to the apex of said cone, the length and diameter of said surface of revolution being such that the impedance of said antenna is substantially a pure resistance of substantially constant magnitude over a wide range of frequencies.

4. An antenna comprising two surfaces of revolution in the form of cones symmetrically located with respect to a common axis passing through their apices, the length of each surface of revolution as measured from its apex to the end being at least .23 wavelength at the operating frequency, each surface of revolution making an angle of 45 with said common axis, said surfaces of revolution presenting at their apices substantially a pure resistance over a wide range of frequencies.

5. A short wave antenna system comprising a surface of revolution in the form of a cone mounted vertically with its apex pointing downwards, and a horizontal reflecting surface mounted below the apex of said cone, said reflecting surface being at zero radio frequency potential, said cone being so constructed and so arranged with respect to said reflecting surface that the impedance of said antenna is substantially a pure resistance over a wide range of frequencies.

6. An antenna system as defined in claim 1, characterized in this that a coaxial transmission line connects said high frequency apparatus to the apices of said cones, said transmission line extending along the axis and through one of said cones, the outer conductor of said line being coupled to one apex, and the inner conductor of said line being connected to the other apex.

, PHILIP S. CARTER.