US1995152A - Antenna - Google Patents

Description

March 19, 1935. H, J, LQFTIS 1,995,152 Q ANTENNA Filed Nov. 19, 1930 2 Sheets-Sheet 1 LUNG:

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m m m ['11 mm EE] III [II LLI [II III III III Patented Mar. 19, 1935 UNIT ED S T ATES ANTENNA Homer J. Loftis, Dayton, Ohio, assignor, b'ymesneassignments, to Radio: Corporation of America, New York, N. Y., a corporation of Delaware Application. November 19, 1930, Serial No. 496,605-

3 Claims. (Cl. 250-33) gested sections such as apartment houses; skyscrapers etc, it oftentimes becomes necessary to have a long lead-in that picks up disturbances that are usually local in origin and that are of such-a magnitude that their energy level is substantially equal to-and even greater than that of the desired incoming signal.

An object of this invention isrto reduce the undesirable disturbances'usually local in source that are picked up by long lead-ins. This has been accomplished by providing an aerial'and a counterpoise properly spaced and ,connectedto the primary winding of a transformer by means of a pair of lead-inslocatedin close proximity to each other and preferably twisted; said transformer,

having means for counteracting both electrostatically and electromagnetically the disturbing voltage impulses picked up by thelead-ins.

In the present modificationboth theaerial and the counterpoise are mounted at arelatively large distance from the earths' surface so'that the magnitude ofthe disturbing signals or impulses cutting. the aerial andthecounterpoise is relatively small.

Further objects=and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of one form of the present invention is clearly shown.

In the drawings:

Fig. 1 discloses a preferred modification of the present invention.

Fig. 2 discloses another modification.

Fig. 3 is a detailed view of a transformer.

' Fig. 4 discloses another modification.

In the drawings the reference character 10 indicates an aerial and 12 a counterpoise. The aerial 10 and the counterpoise 12 may be suspended between a pair of supports 14 and 16 and insulated therefrom by means of the insulators 18, 20, 22 and 24. The aerial 10 and the counterpoise 12 are, for all practical purposes, equivalent in that each picks up signals, different in amplitude however, that are transferred to the radio receiver. The aerial 10 is connected by a lead-in 26 to a terminal 28 of the primary winding 30 of a transformer 32 and the counterpoise 12 is connected by a lead-in 34 to the other terminal 36 of the primary windings 30. The terminals 44 and 46 of the secondary winding are connected to the input terminals '45 and 47- of a radio set shown conventionally at 49; r

The primary winding 30 has a center t'apiifi con nected to ground'at 40. Instead of acenter't'ap any equivalent voltage equalizing meansmay be' used, as" for example the onediscl'osed in Fig. 3, which will be described later. Itcan be readily seen that disturbing signals picked up by" the lead-in 26 and by the lead-M84 generate equal voltages between the terminals 28'and"38,--andv 36 and. 38, respectively, but opposite in phase'r'ela PAT-EN FF-ice:

tion so that electromagnetically the two voltagesare balanced out in the primary winding 30 so 'asto have practically no effect upon the" secondarywinding 42. This is probably the caselfor thereason that thetwo lead-ins are in substantially the same electrostatic and electromagnetic field throughout their entire length. Theincoming" signals cause voltage impulses in-th'e aerial. 1 .:0 designated by E1 and thevoltageimpulsesdn-the counterpoise 12 designated by E2. As the source of disturbance is usually near the ground and as this disturbancedecreases'very rapidly as the dis-' tance from the disturbance increases tlie-difference in voltages E1 andE-due t'o the disturbances is-very small whereas the voltage difference due to the selected-incoming signal is relatively large so" that the-energy level of the disturbances is-f-ar below the energy level of the selected incoming signal.

If a shield or the like is not used to neutralize the electrostatic forces acting between the primary and the secondary of the transformer 32 it can be readily seen that there will be a capacity coupling between the terminal 28 and one terminal 44 of the primary and secondary windings respectively, as best seen in Fig. 3. This will not be offset by the capacity between the terminals 36 and 46 for the reason that the terminal 46 being grounded is substantially at ground potential at all times. In my preferred modification, as seen in Fig. 1, I have overcome the capacity coupling between the terminal 28 and. the terminal 44 by inserting an electrostatic shield 48 grounded at 40. This electrostatic shield, as is well known to those skilled in the art, counteracts the electro-. static or capacity coupling but has no substantial effect upon the electromagnetic coupling as the electrostatic shield is made from a non-ferromagnetic material. such as copper, tin foil or the like. Where the primary and secondary windings are wound one on top of the other this shield is placed between the windings. In Fig. 2 the antenna 10 and the counterpoise 12 have been connected by the lead-ins 50 and 52 to separate primary windings 54 and 5 6 of a transformer having secondary winding 62. The primary windings are connected in series and wound in such a direction with respect to each other that when currents simultaneously enter the windings from the lead-ins and leave to the ground at 40, the magnetic fields set up by those currents in the windings oppose each other. The secondary winding has its terminals connected to the antenna post 64 and the ground 66 of a conventional radio disclosed at 68. Instead of using a shield as in Fig. 1 the electrostatic coupling between the ends of the coils 54 and 62 adjacent to the terminals 70 and 72 is neutralized by the'ground 74 of the winding 56, that is, the high potential end of one coil in the primary is adjacent to the ground potential end of the other primary coil.

This modification gives very good results for some installations.

Instead of connecting the center tap 38 on the primary to ground as disclosed in Fig. 1 the tap found in the midpoint of a high resistance 82 having its terminals connected to the lead- ins 84 and 86 causes the electromagnetic neutralization as bestv seen in Fig. 4. If this method is used for causing the electromagnetic neutralization it is necessary to use grounded electrostatic shield 88 between the primary and secondary windings, as shown, in order to overcome the electrostatic cou- 1-' pling. If not, undesirable disturbances picked up by one of the lead-ins will be transferred to the radio receiver electrostatically. In this modification any suitable radio frequency transformer maybe used by providing this resistance which -may in certain cases be provided with an adjustable center tap that may be adjusted for complete electromagnetic neutralization of equal voltage impulses impressed upon the opposite primary terminals. I 7

While theform of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be. adopted, allcoming within the scope of the claims which follow.

What is claimed is as follows:

1. An antenna circuit for a radio receiver remotely located, comprising in combination, an aerial, a counterpoise located near the aerial, a

transformer having its secondary winding conmoans nected to the input terminals of the radio re ceiver, transposed lead-ins connecting the aerial and the counterpoise to opposite terminals on the primary winding of said transformer, said leadins picking up substantially equal disturbing voltage impulses but unequal signal impulses, means for electromagnetically neutralizing said disturbing impulses including a common connection to ground from an intermediate electrical point of the primary and one terminal of the secondary and a grounded shield interposed between the primary and secondary windings of said transformer whereby said undesired impulses are not transmitted to the radio receiver electrostatically, and whereby only the signal impulses received by the aerial and the counterpoise are received by the radio receiver.

2. An antenna circuit for a remotely located radio receiver, comprising in combination, an aerial, a counterpoise located near the aerial, a

transformer having its secondary winding connected to the input terminals of a radio receiver, lead-ins connecting the aerial and the counterpoise to terminals on the primary winding of said transformer, said lead-ins comprising a pair of closely associated insulated conductors, an

electrostatic shield interposed between the primary and secondary'windings of said transformer, said electrostatic shield being connected to one terminal of the secondary of the transformer.

3. An antenna circuit for a remotely located radio receiver, comprising in combination, an

aerial, a counterpoise located near the aerial, a'

transformer having its secondary winding connected to the input terminals of a radio receiver, lead-ins connecting the aerial and the counterpoise to terminals on the primary winding of said transformer, said lead-ins including insulated and closely associated conductors, an electrostatic shield interposed between the primary and secondary windings of said transformer, said electrostatic shield being connected to one terminal of the secondary'of the transformer, and an'impedance connected across the primary of said transformer, said impedance having a variable tap intermediate its extremities and connect ed to ground. I

HOMER J. LOFTIS.

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