US2240298A

US2240298A - Dipole antenna

Info

Publication number: US2240298A
Application number: US264294A
Authority: US
Inventors: Harold J Heindel; Milton B Sleeper; Cawein Madison
Original assignee: ANDREA RADIO CORP
Current assignee: ANDREA RADIO CORP
Priority date: 1939-03-27
Filing date: 1939-03-27
Publication date: 1941-04-29
Anticipated expiration: 1958-04-29

Description

April 29; 1941.

H. J. HEINDEL ETAL DIPOLE ANTENNA Filed March 2'7, 1939 Bi/a 60 ohms 121112272622; M116 Zae per fliazuezifi/ INVENTOR6 WM ATTORNEY I Patented Apr. 29, 1941 DIPOLE ANTENNA Harold J. Heindel, Flushing, Milton B. Sleeper, New York, and Madison Cawein, Manhasset, N. Y., assignors to Andrea Radio Corp, Woodside, N. Y.

Application March 27, 1939, Serial No. 264,294

4 Claims.

The present invention concerns electro-magnetic wave antennas and in particular a novel form of dipole antenna useful at ultra high frequencies.

One object of the present invention is to provide an improved dipole antenna.

Another object is to provide a dipole antenna having improved electrical characteristics and at the same time improved mechanical characteristics. Y

A further object is to provide a novel dipole antenna adapted to simple adjustment for optimum directional and frequency response characteristics.

A still further object is to provide a novel ligh ning arrester in conjunction with the impedance matching means of a dipole antenna.

These and other objects of the invention will be evident from the detailed description of the various figures of the drawing.

A dipole antenna of the type utilized in the present invention comprises two equal, oppositely directed, horizontal antenna elements. The two antenna elements are mounted coaxially and spaced apart by a small distance. Lead-in wires are connected to the inner ends of the two elements.

The present antenna embodies a number of novel features. The two antenna elements are mounted on a central weather-proof housing containing preadjusted impedance matching elements, the connections to the lead-in wires and a lightning arrester. The housing is mounted on a coupling block adapted to fit over the end of an antenna pole. he two antenna elements are further supported by means of stream-lined arms mounted in the coupling block and supporting the antenna near its outer ends. A coupling section is provided in the pole allowing the antenna to be rotated to an optimum receiving angle after which it may be permanently fastened in position. The outer ends of the antenna elements are scored at points at which they may be out-off to provide shifting of the optimum or average frequency response point of the antenna. We prefer to call our novel antenna a teleceptor.

In the drawing:

Fig. 1 shows a complete teleceptor antenna constructed according to the present invention.

Fig. 2 shows a curve of impedance of the present teleceptor antenna.

Fig. 3 shows an equivalent circuit of the present teleceptor antenna.

4 shows one form of lightning arrester incorporated in the present teleceptor system.

Fig. 5 shows an alternative lightning arrester in the teleceptor antenna system.

In Fig. 1 is shown a dipole teleceptor antenna according to the present invention. The two dipole elements I and 2 are mounted on insulators 3 and 4. Insulators 3 and 4 are symmetrical hemispherical shaped and enclose a weatherproof space by clamping together with a bolt ll, block I9 by means of bolts I and 8 and an annular weather-proofing washer Is. In opposite ends of insulators 3 and 4 are mounted the metal fittings H and i5 which are spun over on the outside to provide a water-proof seal. Fittings II and I5 are provided with blind tapped holes IQ and i4 adapted to receive the threaded ends of antenna elements 2 and I. Securely mounted on elements I and 2 are flanges I3 and 9 adapted to press against fittings I5 and I I providing a good electrical contact between the antenna elements and the fittings and providing mechanical stability and locking. Fitting II and I5 are provided with inwardly directed projections l2 and it such that the separation between the ends of projections l2 and I6 provides a predetermined electrical impedance over the high frequency operating range. Projections I2 and It also provide terminations for a transmission line iii-32 to a television or other receiver. The transmission line ends are soldered to projections I2 and IE to provide low resistance connections. The weatherproof housing provided by insulators 3-4 protects these connections from deterioration.

Insulator housing 3-4 is mounted on a mounting block Iii by means of bolts 1 and 8 passing thru feet 5 and 3. Block I9 is provided with two horizontally directed

holes

20 and 23 and a downwardly directed hole 26. Wooden support rods 2i and 24 tapered at their outer ends to reduce wind resistance are fitted into holes 2%] and 23. Near the outer ends of. supports 2I and 24 are mounted

vertical insulators

22 and 25 adapted to engage antenna elements 2 and I near their upper ends. The upper section 21 of a vertical supporting pole fits into hole 25. A second section 29 of the vertical pole is provided. The two vertical pole sections 21 and 23 are interconnected by means of a coupling 28. The lower end of coupling 28 is fastened to pole 29 while the upper end is initially free to allow rotation of the antenna into the most favorable directional position. When the desired position is found the upper pole is secured to coupling 28 by passing a pin or screw it thru the two.

The distance between supporting

insulators

22 and 25 is made such that the shortest antenna elements I and 2 to be used project somewhat beyond them. The outer ends of elements l and 2 are scored or partly cut thru at

points

34 and 33 to provide an easy means of removing sections of these elements as will be more fully described below.

Fig. 2 shows a plot of the impedance of the dipole antenna at the ends of fittings I2 and it as the sum of the lengths of elements I and 2 are varied plotted in terms of wavelength cor- Antenna elements to be broken oil at score ielei lsion bands points 44-50 megaeycles 50*56 megacycles 44-50 niegacycles }Usc full 60 inch lengths.

Remove antenna elements beyond 52 inch 50-56 megacycles" score points.

66-72 megacycles 50-56 megscycles. o

p r l 7 (H2 mcgacycles Remm c at inch score loints 44-50 megacyeles 50-56 megacycles" 66-72 megocycles. 78-84 megocyclos. 84-90 megacycles R move at 45 inch score points.

Due to proximity effect the apparent impedance of the antenna. will be somewhat greater than the theoretical value as shown in Fig. 2. Also there will be some unavoidable mis-matching due to operating over a band of frequencies. A good practical matching impedance for the antenna has been found to be 100 ohms. Using this impedance to terminate the receiver end of the transmission line and using a 100 ohm impedance line provides a coupling to the antenna over the bands as shown which will not introduce objectionable reflections. Large values of mis-match at either end of the transmission line will set up reflections which may be visible in the television picture as extraneous images displaced from the primary image. The inner ends of fittings l2 and t5 should be separated approximately 1 inch as greater separations will increase the impedance of the antenna as seen from the transmission line input terminals. Thus antenna elements each 60 inches long scored at 54, 50 and 45 inches may be quickly adapted to operate most efficiently over the various frequency hands given. It will be clear that many other combinations are possible. In the example given the

insulators

22 and 25 may be located at approximately 42 inches along each antenna element.

Fig, 3 shows an equivalent circuit of the dipole antenna shown in the present disclosure. Each element has a series inductance L, and equivalent lumped capacity at the outer ends of C and a lumped capacity at the inner ends of nC. The signal voltage is assumed to he introduced in series with each element at points x and :0. With overall length equal to L the impedance Z at J is as was shown in Fig. 2. The transmission line T is attached at J and looks into an impedance Z.

Fig. 4 shows a lightning arrester enclosed within the weather-proof housing 3-4. A conducting element is located within the housing and is symmetrically located to provide equal gaps between it and fittings I2 and IS. Element 35 is connected to ground G by means of a lead 36.

Fig, 5 shows an alternative lightning arrester comprising conducting elements 31, 38 and 39 located within a housing M! which may be scaled and evacuated or may be filled with a 10W pressure gas. Element 39 is connected to ground G and is spaced symmetrically with respect to elements 3'! and 38 which are connected to transmission line wires 3| and 32 respectively. Transmission line 3l32 continues on to a television receiver or other utilization means 6 1.

While only one embodiment of the invention together with a few modifications has been shown it will be evident to one skilled in the art that many modifications are possible Without departing from the invention as set forth in spirit and scope in the appended claims.

What is claimed it:

1. In a. high frequency antenna system, the combination of, a pair of tapered conductors each threaded at one end and scored at a plurality of predetermined points near the other end, a housing comprising a pair of cup-shaped insulators each carrying a fitting at the apex and means for clamping said insulators together at their peripheries to form an enclosed space, said fittings including inwardly directed projections to form a predetermined air-gap within said housing and outwardly directed threaded sockets to receive said threaded conductors, and a two conductor transmission line terminated upon said projections.

2. In a high frequency antenna system, the combination of, a pair of linear conductors, a hemispherical housing including fittings for holding said conductors in a substantially straight line, a plurality of score marks at predetermined points near the outer ends of said conductors, a support pole, a pair of support arms, a coupling block for holding said arms in perpendicular relation to said pole, means for mounting said housing on said block, means for supporting said conductors from said arms at points between said score marks and said housing and transmission line electrically connected to said fittings within said housing.

3. In a high frequency antenna system, the combination of, a pair of linear conductors, a hemispherical housing including fittings projecting thru the sides of said housing for holding said conductors in a substantially straight line, a support pole, a pair of support arms, a cou pling block for holding said arms in perpendicular relation to said pole, means for mounting said housing on said block, means for supporting said conductors from said arms, a coupling section in said pole to permit rotation of said arms, and means for clamping said coupling to prevent rotation of said arms.

4. In a high frequency antenna system, the combination of, a housing comprising a pair of cup-shaped insulators each carrying a fitting at the apex and means for clamping said insulators together at their peripheries to form an enclosed space, said fittings including inwardly directed projections to form a predetermined air-gap within said housing and outwardly directed sockets for holding a pair of linear conductors in suhstantially in-line relation, and a two conductor transmission line clectricaily terminated at said projections.

HAROLD J. IIEINDEL. MILTON SLEEPER. MADISON CAWEIN.