US2575377A - Short wave antenna - Google Patents

Description

Nov. 20, 1951 R J. wo.q 2,575,377

SHORT WAVE ANTENNA Filed Nov. 13, 1945 3wuwvvtom ROBERT J. WOHL Patented Nov. 20, 1951 SHORT WAVE ANTENNA Robert J. Wahl, UnitedStates Navy Apiflication November 13, 1945, Seflal'N'o. e2s;337

(Granted. under the act of March 3, 1883, as amended' April 30, 1928; 370 O. G. 757) 5 Claims.

This iifirention re1ates to an antenna for transmission er reception of short wave radio energy.

It isone object of this invention 130 provide a short.wave radio antenna suitable 101 transmissich o1 recep'tion of radio waves having any frequency within.a;wide frequency band.

It is another object of this invention to provid6 such an antenna smal1 in size and simple in constrution.

The invention Will be frther explained with reference 110 the attached d1awing, in which'.

Figure 1 showsone embodimeno of this inve'ntior1and Figure 2 shows. a second embodiment of the invention.

In accordahce.with the. present invention an ahtenna for transmissionor for reception of short wav.e radio energy is.provided comprising a broad conductorof I:hin cross section arranged. in the f0'rm of a helix having closely spaced adjacent turns, the longitudinal dimension of the helik being a small fraction of the operating wave-length and the transverse dimension 0f the helix being afraction the aforesaid longitudinal dimension. Additional loading of the antenna is efiected by means of a cap shaped conductor connected to one end of the helix.

Referring now 110 the drawings, and in the first instance to the embodiment shown in Figure 1, a thin strip III of a conducting material such as copper is wound helically upon a dielectric form II. The resulting he1ix is fed ab one end I2 by another conductor I3. Connected to the other end I4 is a cap-shaped member I5, formed of a conducting material such as copper.

In Figure 1 dielectric form II and member I5 comprise an airfoil Which is attached to a fuselage I6 of a vesse1 or a missile 130 be propellecl through space. The antenna shown may be used for any application requiring reception of radio signals over a fairly broad band. Since conducting strip I 0 is of very sma1l thickness and can be caused to adhere directly to the surface of form II, the contours of the airfoil will not be spoi1ed by the presence of the antenna. For purposes cf illustration the thickness cf conductor II) is great- 1y exaggerated in the drawing. Conductor I0 and the airfoil may be covered, if desired, by a thin coat of a dielectric such as nlastic or paint to he1p secure conductor I0 in nlace.

For a given airfoil, the width of the freauency band for which the ant-enna embodying this invention is suitable will be determined largely by the width of conductor III, the spacing of the turns in the helix, am]. the dimensions of member I5, The frequency a1: which quarter waVe 'resO-' nance occurs will be determined by the Width pi c0ndut0r III, the total length of conduct0r I0,; the nuinber of tu'rns in the helix and their spa eing", and th'e dimensions cf member I5 which 1'oadS the antehha. Not all thesie factors a're independrtends through an apert'ure in fuse1age I6, -bi'ng secured to. the fuselage in a suitable manrir.

The embodiment of Figu1"e 2 is designed t0 be placed entirely within the s'u1face cf an irfoil.-

In I1his embodiment Condu(ztor III is helicll3'r' W0und unon a frame comprising two spaced'ihsulating members I8 which are di'electric x'nateri'all As in the embodimrlt of.

such as polystyrene. Figure 1, one end I2 of conductor II! is com'1tected to feed cnnductor I3, and the other end I4 of. conductor I5 is connected mechanically and 616G- trically cap-shaped member I5 which is a part of the external surface of the airfoi1.

The Same factors influence the bandwidth and resonant frequency of the embodiment of Figure 2 as infiuence these two characteristics in the embodiment of Figure 1. For an actua1 specimen cf the arrangement of Figure 2,. the standing wave ratio over ehe frequency band 34.0 to 41.7 mc./sec. was measured to be less than 5 to 1, which was found to be suitable for the reception of radio waves over this band. The standing wave ratio for this specimen was also found to be lass than 2 to 1 from 36.6 mc./sec. to 38.6 mc./sec. The helical shape and capacitive toploading cf the antennas of Figures 1 and 2 result in considerable foreshortening efiect, as is exampled by a comparison of the physical and e1ectrical lengths of the abovementioned actual speciman of the antenna. In this specific embodiment, the specimen, a helix of 22 /2 turns, exhibited quarber wave resonance at 37.8 mc./sec. although its physical length of 14%" represented onl V about /23 of one wave length at this frequency.

It will be understood that the embodiments described and shown are exemplary of this Invention, the scope whereof may be ascertained with reference to the appended claims.

The inventio=n described herein may be manufactured and used by or for the Governrnent of I;he United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is clalmecl is: 1. A quarter wave resonant antenna fort transmission or reception of short wave radio energy comprising a conductor in the form of a helix having adjacent turns spaced by an amount substantially equal to the conductor width, the longitudinal dimension of said helix being less than the wave length of the operating wave, the transverse dimension of the helix being a fraction of said longitudinal dimension, the conductor having a broacl, thin cross-section, and a cap shaped conductor connected to one end of said helical conductor.

2. An antenna for transmission or reception of sho'itwave radio energy comprising a supporting stmcture of airfoil cross sectional characteristics, a conductor in the form of a spiral having. adjacent turns spaced by an amount substantially equal to the Conductor width wound on the supporting structure, the longitudinal dimension of said spiral beim; less than a quarter of the wavelength of the operating wave, the maximum transverse dimension of the spiral 'being a fraction of said longitudinal dimens'ion, and a cup shaped conductor disposed wound on the supporting structure, the longitudinal dimension of said spiral being less than a 'quarter of the wavelength of the operating wave, the maximum transwarse dimension of the spiral;being a. fraction of said longitudinal elimen sion a. cup shaped conductor disposed at one end of the supporting structure conductively, connected to one end of the spiral conductor, and means connecting another end of the spiral conductor to the radio energy transmitter or receiver.

4. An antenna comprising a conductor wound in the form of a helix having spaced adjacent turns, the longitudinal dimension of said helix being a small fraction of the wave length 0f the operating wave, the transverse dimension cf the helix being a fraction of said longitudinal dimension, the conductor having a broad, thin cross-section, and a cap shaped conductor counected to one encl of saiol helical conductor to further load the antenna.

5. An antenna comprising a supporting structure of airfoil cross-sectional characteristics a conductor wouncl on the supporting structure in the shape of a helix having spaced adjacent turns, the longitudinal dimension of said helix being less than a quarter of the wavelength of the operating wave, the maximum transverse dimension of the helix being a fraction 0f said longitudinal dimension, and a cup shaped comductor disposed at one end of the supporting structure conductively connected to one end of the helix conductor.

ROBERT J. WOHL.

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

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