US2632107A - Television antenna - Google Patents

Description

March 17, 1953 J.-'HLIVJAK 2,532,107

TELEVISION ANTENNA I Filed 001$. 23, 1952 2 SHEETS-SHEET. l

IN V EN TOR. Jab flak/ ul! BY March 17, 1953 J. HLIVJAK 2,632,107

TELEVISION ANTENNA Filed-Oct. 23, 1952 2 SHEETS-SHEET2 I N V EN TOR. \jkfi flzz'gez/r BY m Mm \j zi arvzew UNITED S'iAiis TELEVISION ANTENNA John Hiivjak, Chicago, 111., assignor to True Tronics, Inc., Chicago, 111., a corporation of Illinois Application October 23, 1952,'Serial No. 316%01 8 Claims. (Cl. 25t-33) l 2 This invention relates to antennas :and, more A further object of my invention is to afford a specifically, to antennas which are particularly novel dipole antenna having two end portions well adapted for use with both V. .H. F. and on which equalization of the wave lengths is im- U. H. F. television broadcast band receivers and proved.

.FM broadcast band'receivers. 5 A further object is to aiiord a novel antenna Various types of'antennas, both for indoor and of the aforementioned type which embodies a outdoor use, haveheretofore been'knownin the novel auxiliary antenna which affords improved :art. However,such antennas as have beenhereholding of the wave length and adds to the gain tofore known in the art have had several in- 'of-the antenna. heren't disadvantagessuch as,for'example, being Another object of my invention is to provide large and bulky in size; being difiicult to manua novel antenna which embodies an auxiliary anfacture and assemble; and being inefficient in tenna which is effective and affords improved operation. It is a primary object of my invenperformance in the so-cailed standard very tion'to overcome such disadvantages and to afhigh frequency wave lengths and also in the ford a novel emcient antenna which is relativel5 ultra-high frequency wave lengths. ly small in sizamay be readily and economically Yet another object of my invention is to promanufactured commercially, and maybe :quickly vide an antenna of the aforementioned type and easily assembled. which embodies a main dipole antenna and an .Another important object of my invention is auxiliary antenna constituted and arranged in to provide an-antenna oi-theaforementioned type 0 a novel and expeditious manner. which affords "an especially effective andefficient An object ancillary to the foregoin is to afindoor'antenna but Whichyif desired, may also ford a novel antenna embodying a novel auxbe used outdoors to afford a novel, effective outiliary antenna disposed in a plane extending be- .door antenna. tween the opposite longitudinal sides of a folded Another object of my invention is to afiord a dipole antenna. novel antenna of the aforementioned type which, Another object of my invention is to aiford a though relatively small in size, has improved gain novel antenna of the aforementioned type which characteristics. embodies, as a part thereof, a novel auxiliary an- A further object is to afiord'an antenna which tenna embodying two bars disposed in substanis efiicient in operation without requiring the tially end-to-endrelation with the adjacent ends antenna to be mounted high'in the air. disposed in spaced relation to each other and the Another object of my invention is to provide outer ends thereof electrically interconnected by a novel antenna which, in most instances, does a conductor of relatively high resistance. not require change of location when the receiv- A further object of my invention is to afford a ing channel ischanged in order to afford proper 36 folded dipole antenna having slidable sections receptionand embodying an auxiliary antenna disposed Many 'th antennas heretofore known in the between the bars of the trombone in a manner r n p i lly he in r n a r hi hto effectively capture the wave length of the 1y sensitive to the gain or interference afforded transmitting station.

v' b y f person wh n h tperson i Other andfurther objects of the present inm n r st n some instances, vention will'be apparent from the following deelenwhen person 15 'Standmg relatively scription and claims and are illustrated in the close proximityto theantennasuch as, for exaccompanying drawings which by way of i11uS ample, when the'person is tuning thereceiver. nation, Show a preferred embodiment of the h makes (hm-cm}; to properly tune t present invention and the principles thereof and ceiver for good reception because of the different What I now consider to be the best mode in receiving characteristics encountered when the which I have contemplatpd applying these 1mm person is in close proximity to the antenna and Dimes ofher embodiment; of the invention when he is at the normal, and considerably greatbodylng the same or equivalent prmciples may er, distance therefrom for viewing the program. so be used and Structural changes may be made as It i an cb'ect of m invention to fiordan 3 y desired by those skilled in the art Without deantenna which is relatively non-sensitive to a person maneuvering the isamg or Standing in partingfrom the present invention and the purview of the appended claims close proximity thereto. 7

Another object of .my invention is-tojafford a 5x the g A Fig. 1 15 a front elevational view of an annovel antenna of the aforementioned type which is less susceptible to .electrical and automotive tenna embody the p p s Of y mvelfltlon;

disturbances thaniantennas. heretofore known in Fig. 2 is a top plan View of the antenna shown thee-rt. in Fig. 1;

Fig. 3 is a rear elevational view of the antenna shown in Fig. 1;

Fig. 4 is a detail sectional view taken substantially along the line 44 in Fig. 3;

Fig. 5 is a detail elevational view of a portion of the antenna shown in Fig. 3;

Fig. 6 is a detail sectional view taken stantially along the line 66 in Fig. 5;

Fig. '1 is a detail sectional view taken stantially along the line 11 in Fig. 5;

Fig. 8 is a detail sectional view taken stantially along the line 88 in Fig. 5;

Fig. 9 is a detail sectional view taken substantially along the line 9-9 in Fig. 5; and

Fig. 10 is a detail sectional view taken substantially along the line |-lfl in Fig.

To illustrate the principles of my invention, an antenna 20 comprising a preferred embodiment of my invention, is shown in the drawings. The antenna 20 comprises, in general a dipole folded antenna 22 and an auxiliary antenna 24 mounted on a stand 26 and constituted and arranged in a novel and expeditious manner to afford a novel, and highly effective unitary antenna for receiving television broadcasts as will be discussed in greater detail hereinafter.

The dipole folded antenna 22 embodies two pairs of bars 3| and 32, and 33 and 34, respectively, in the form of hollow tubes mounted on a terminal block or mounting block 35, and projecting outwardly therefrom in opposite directions. Two substantially U-shaped slides 36 and 31, each having two spaced, substantially parallel legs 36a and 36b, and 31a and 31b, respectively, are mounted in the two pairs of tubes 3|-34 with the legs 36a, 36b, 31a and 31b mounted in the tubes 3|, 32, 33 and 34, respectively.

The mounting block 35 may be made of any suitable dielectric material such as, for example, porcelain or wood and has a front face 35a and a rear face 3517, Figs. 1 and 3. Three substantially parallel grooves 4|, 42 and 43, Figs. 5 and 6, are formed in the rear face 35b of the mounting block 35 and are normally disposed in substantially horizontal position, the groove 4| being formed in the upper end portion of the mounting block 35, the groove 43 being formed in the lower end portion of the mounting block 35, and the groove 42 being formed in the mounting block 35 midway between the grooves 4| and 43.

The bars or tubes 3| and 33 are mounted in the groove 4| with the respective inner terminal end portions 45 and 46 thereof terminating in spaced relation to each other, Fig. 5, and with the respective outer terminal end portions 48 and 49 thereof projecting in opposite directions substantially horizontally outwardly from the mounting block 35. The bars 3| and 33 are releasably secured in operative position in the groove 4| by bolts 5| and 52, respectively, and nuts 53 and 54, the bolts 5| and 52 extending through the mounting block 35 and the respective inner end portions of the bars 3| and 33, Figs. 5 and 8.

The bars 32 and 34 are similarly mounted in the groove 43 with the respective inner terminal end portions 56 and 51 thereof disposed in spaced relations to each other and the respective outer terminal end portions 58 and 56 thereof projecting in opposite directions outwardly from the mounting block 35. The bars 32 and 34 are releasably secured in the groove 43 by nuts 6| and 62 mounted on bolts 63 and 64 which subsub-

sub-

project through the mounting block 35 and the inner end portions 56 and 51 of the bars 32 and 34, respectively.

The tubes 3|-34 may be formed of any suitable electrically conductive material, such as, for example, aluminum and the slides or trombones 36 and 31 are formed of suitable material such as, for example, aluminum bar stock. The legs 36a, 36b, 31a and 31b of the slides 36 and 31 are of such diameter that they fit into the respective tubes 31-34 with a snug sliding fit so that good electrical contact is afforded between each leg 36a, 36b, 31a and 31b and the respective tube 3|34 into which it is fitted.

The auxiliary antenna 24 embodies two elongated bars 1| and 12, Figs. 1 and 2, made of any suitable material such as, for example, aluminum tubing mounted in the groove 42 in the mounting block 35 with the inner terminal end portions 14 and 15 thereof, respectively, disposed in spaced relation to each other, Fig. 5, and the outer terminal end portions 11 and 18 of the bars 1| and 12, respectively, projecting outwardly in substantially opposite directions from the mounting block 35. Like the bars 3|-34, the bars 1| and 12 are releasably se cured in the mounting block 35 by nuts and bolts for quick and easy assembly and disassembly, bolts 82 and 83 extending through the mounting block 35 and the respective inner end portions 14 and 15 of the bars 1| and 12 and having nuts 8| and 82 mounted thereon.

A tension coil spring 85, Figs. 2 and 3, having books 86 and 81 at the opposite ends thereof, is normally mounted in tension between the bars 1| and 12, the hook 86 being hooked into the open outer terminal end 11 of the bar 1|, and the hook 81 being hooked into the open outer terminal end 18 of the bar 12. The spring 85, which forms a part of the auxiliary antenna 24, is of particular importance in my novel antenna to which it is used in the reception of broadcasts transmitted on ultra-high frequency wave lengths. It not only affords a greater horizontal spread for the reflector antenna which is of importance in the reception of U. H. F. waves but, of course, aifords a greater total antenna length and surface. In addition, the spring 85, being constructed of coiled relatively thin wire, affords a relatively long total length of wire of relatively high resistance which forms the only electrical connectioi between the two sides L and R of the antenna 20.

It will be remembered that the spring 85 is of particular importance when the antenna 20 is used for receiving U. H. F. wave lengths. However, although under certain conditions when my novel antenna 28 is used in the reception of V. H. F. wave lengths the spring 85 may be removed from the bars 1! and 12 and the antenna 26 successfully used without the spring 85 such as, for example, in areas where the signal to be received is what may be called average, that is, neither weak nor strong, the spring 85 does improve the reception obtained with my novel antenna 20 of V. H. wave lengths, especially in areas of strong signals and in the fringe areas where the signal is weak. In the areas where the signal is strong the spring 85 prevents the flooding of the antenna heretofore common with antennas known in the art, and in the fringe areas where the signal is weak the spring affords an effective additional antenna surface which is of assistance in pulling in the signal.

The inner end portions 45 and 14 of the bars 3! and II, respectively, are electrically connected by means of a conductor-of any suitable material, such as, for example, a strip of copper sheet 9|. Figs. and 6, mounted on the bolts SI and 82 and releasably secured thereto by means of the nuts 53 and 80, respectively. Similarly, the inner end portions 46 and I5 of the bars 33 and I2 are electrically connected by means of a conductor such as a strip of copper sheet material 92, Figs. 5 and '7, mounted on the bolts 52 and 83 and held thereon by the nuts 54 and BI, respectively.

Two lead wires 94 and 95, Figs. 1, 3 and 5, are mounted on the bolts 63 and 64, respectively, and are held in good electrical connection with the inner end portions 56 and 51 of the bars 32 and 34, respectively, by the nuts BI and 02. The lead wires 94 and 95 aiiord the conductors by means of which the antenna may be connected to the antenna terminal posts of the television receiver with which it is to be used such as, for example, the terminal posts 91 and 98 on a television receiver 39, a corner of which receiver is shown in Fig. 1.

The stand 26 of the antenna shown in the drawing embodies a supporting base IOI, Figs. 1, 2, and 3 and l, having an upwardly opening, substantially rectangularly shaped pocket I02 formed therein. An L-shaped mast 04 of substantially rectangularly shaped cross section, and having a normally vertically disposed leg I05 and a horizontally disposed leg I05, Figs. 1, 4 and 6, is mounted on the supporting base II with the lower end portion of the leg I05 disposed in relatively close fitting relation in the pocket I02. The horizontal leg I06 of the mast I 54 is bifurcated having an elongated slot I08 formed therein which extends inwardly from the outer terminal end of the leg I00. Near the outer terminal end portion thereof, the slot N38.

HM and Ii ia and two outwardly diverging legs Ii 31) and H41), respectively, are mounted in a recess IIB formed in the central portion of the rear face T52) of the mounting block 35, Figs. 5'

and 6', and is held in position therein by bolts II8 and nuts II9, the bolts extending throughthe mounting block 35 and the legs I I3!) and I I41 in position to hold plates II 3a and II 4a of the v bracket plates H3 and H4 in substantially parallel spaced relation'to each other. is mounted between the legs IISa and II4ct of the bracket plates H3 and H4 and is held in position thereinby a rivet I23 extending through the legs Ba and HM, Figs. 6 and 10.

In mounting the mounting block 35 on the mast I05, the leg I05 of the mast I04 may be slid into position between the legs lI3a and Ilsa of the bracket plates I I3 and I I4, and the roller I2I may be moved inwardly through the guideway A roller I2! Iiil into the socket I09, which is complementary.

in shape thereto and wherein the roller I2I is firmly but releasably clamped or gripped between the bifurcations of the leg IE5.

The lowerend of the vertical leg i 05 of the mast I05 may be may be readily shipped in a partially assembled condition wherein it is separated into three units. the dipole folded antenna 22, the auxiliary antenna 24, and the mounting block 35 forming one unit, the mast I04 formin another unit, and the supporting base IOI forming another unit. The antenna may be quickly and easily assembled from such partially assembled condition by slipping the leg I06 of the mast I04 into position in the bracket II2 and then inserting the leg I05 of the mast I04 into the pocket N2 of the supporting base I04. Likewise, the antenna 20 may be quickly and easily disassembled into the aforementioned partially assembled condition by merely pulling the mast I04 out of the supporting base IOI and then pulling the mast I04 out of the bracket I I2.

If desired, of course, the slides 86 and 31 may be removed from the bars 3I-34, and the bars iii-34 and II and i2 may be readily removed from the mounting block 35, and the antenna 20 may be packed and shipped in this more completely disassembled condition. However, the partially disassembled antenna affords a compact shipping package and will be found to be normally suitable for shipment of my novel antenna.

As is best seen in Fig. 2, the bars TH and 72 of the auxiliary antenna 24 each project substantially horizontally rearwardly at an acute angle from the dipole folded antenna 22. Such construction, it has been found, results in better absorption of the wave lengths, and affords better performance than if the bars II and 12 are disposed in the same vertical plane as the ba 3I-34.

Theoretically, it may appear that best performance would be afiorded, at least in the reception of V. H. F. broadcasts, with the bars II and 12 disposed in the same vertical plane as the bars 3i--34. However, I have found that for practical purposes an included angle of from ten degrees to thirty degrees should be maintained between the bars 'iI and i2 and the antenna 22. If the included angle between the bars II and i2 and the antenna 22 is permitted to become less than ten degrees undesirable operating conditions may be obtained and if the angle is per mitted to become greater than thirty degrees too weak a signal is afiordecl. For reception of V. H. F. broadcasts I prefer to use an included angle between the bars II and '12 and the antenna 22 of ten degrees.

As is best seen in Figs. 5 and 10, the inner ter-- minal end portions i4 and I5 of the bars 'II and '52 are flattened to aiTorcl a firm practical support for the remaining portions of the respective bars ii and i2 which'project therefrom at an angle.

I have found that for receiving present-day television broadcasts on standard V. H. F. wave lengths and for receiving U. H. F., I prefer, for practical purposes, to construct the-antenna 20 for use as an indoor antenna as follows:

(I) The bars 3I3i, H and l2 made from aluminum tubing eight and three-quarter inches in length and having an outside diameter of threeeighths of an inch and a wall thickness of thirtyfive'thousandths of an inch, with the outer end portion of the bars 3I--3t rolled to decrease the inside diameterthereoi to an extent where a bar having an outside diameter of one-quarter of an inch may be received with a snug sliding fit;

(2) The slides 35' and 3? made from round aluminum bar stock having a one-quarter inch outside'diameter, each trombone having an over- 7 all length from closed end to open end of nine and five-eighths inches and the closed end to be rounded on a two and one-quarter inch inside diameter;

(3) The mounting block 35 made from porcelain or other suitable dielectric material and having a length of three and five-eighths inches, a width of two and one-quarter inches, and a thickness of one inch.

(4) The bars H and 12 to be mounted in the block midway between the bars 3| and 33 and the bars 32 and 34;

(5) The spring 85 made from spring steel and comprising a closely wound spring having an unexpanded length of ten inches from the outside of the hooks at each end, and having an inside diameter of one hundred and thirty-two thousandths of an inch and an outside diameter of one hundred and fifty-two thousandths of an inch; and

(6) The stand 26 having an overall height of substantially seven and one-half inches.

Such construction it will be seen aifords a relatively small, compact antenna which may be readily packed for shipment in a relatively small package, and which antenna I have found provides improved performance over antennae heretofore known in the art which were considerably larger.

It will be appreciated that variations may be made from the above set forth dimensions without departing from the purview of my invention. However, for the reception of television broadcasts on V. H. F. and U. H. F. wave lengths the construction of my novel antenna would not substantially exceed the following limits:

(1) The bars 3l34, H, and 12 should not be shorter than five inches, nor longer than twentyeight inches; the outside diameters thereof should not be substantially less than one-quarter of an inch and not substantially more than one inch; and the thickness of the walls thereof should not be substantially less than twentyeight thousandths of an inch and not substantially more than thirty-eight thousandths of an inch;

(2) The slides 36 and 31 should not be substantially shorter than three inches in over-all length between the closed and open ends thereof nor substantially longer than thirty-three inches, and, of course, should be of proper diameter to fit snugly into the bars 3l34;

(3) The distance between the outer surfaces of the bars H and T2 and the adjacent outer surfaces of the bars 3l34 should not be less than one-half an inch and not more than three inches; and

(4) The dimensions of the tubes 31-44, II and 12 should always be equal within plus or minus one-eighth of an inch.

I have found that if the length of the bars 3l-34, H, 12, 36 and 31 substantially exceed the aforementioned limits in length too strong a signal results, and if the lengths are substantially less than the aforementioned limits too weak a. signal results.

Likewise, I have found that if the space between the outer surface of the bars H and 12 and the adjacent surfaces of the bars 3|-34 is substantially less than one-half inch too strong a. signal results, and if the space is substantially more than three inches too weak a signal results.

From the foregoing it will be seen that with an antenna constructed in accordance with my invention, a novel antenna is aiforded which hasa left side L anda right-side R when-viewed from the front, as seen in Fig. l, and wherein the left side L embodies the bars 3|, 32, and 1|, the slide 36, and the conductor 9i, and the right side R embodies substantially identical parts, namely, the bars 33, 34 and 12, the slide 31, and the conductor 92. Thus, the antenna 20 comprises a substantially completely split antenna, the only continuity between the left side L and the right side B being the spring which, being of relatively thin, tightly coiled wire, has a relatively high resistance.

Such construction affords improved performance both in the reception of V. H. F. wave lengths and in the reception of U. H. F. Thus, for example, in areas where the signal is strong, and flooding of antennae heretofore known in the art would normally result, the construction of my novel antenna is such that flooding thereof does not result, one principal reason being belived to be because of the absorbing effect of the spring 85.

Also, the spring 85 is of importance in aifording the improved characteristics of my novel antenna in the reception of U. H. R, my novel antenna having a higher gain because the spring coils afford a higher gain area.

As is well known, the impedance of a folded dipole antenna is approximately three hundred ohms, and with the antenna constructed in accordance with the principles of my invention it will be seen that this is divided substantially equally between the right side R and the left side L, the two sides of my novel antenna being substantially separated from each other, only being connected by the spring 85 which embodies relatively great wave length absorbing or holding characteristics, so that current flow through the lead wires 94 and 95 are, under normal operating conditions, substantially equal.

It will be understood, of course, that the slides 36 and 31 may be slid longitudinally inwardly and outwardly relative to the bars 3l34 to thereby adjust the antenna 20 for the reception of different strength signals, and the like.

From the foregoing it will be seen that I have afforded a novel antenna which is partially well adapted for the reception of television broadcasts; which is efiicient in operation and compact in form; and may be readily and economically produced commercially.

Hence, while I have illustrated and described the preferred embodiments of my invention, it is to be understoodthat these are capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within purview of the following claims.

I claim:

1. An antenna comprising dielectric supporting means, four elongated substantially straight bars, each of said bars having an inner end port1on and outer end portion and being disposed in spaced relation to each other with said inner end portion mounted on said supporting means and said outer end portion projecting outwardly from said supporting means, said bars projecting from said supporting means in two substantially oppositely projecting pairs, each of said pairs comprising an upper bar and a lower bar disposed in vertically spaced substantially parallel relation to each other, two substantially U- shaped bars, each of said U-shaped bars having two;elongatedtlegs and being sliclably mounted on a respective one of said pairs of bars in outwardly projecting relation thereto and with each of said legs mounted on a respective bar of said pair for movement longitudinally thereof, two other elongated bars substantially straight throughout their length, each of said other bars having an inner end portion and an outer end portion and being disposed in spaced relation to the other of said other bars and said four bars with said inner end portion mounted on said supporting means and said outer end portion projecting outwardly from said supporting means, each of said two other bars being disposed between said upper and lower bars in a respective one of said pairs and being disposed at a horizontal acute angle to said respective pair, means selectively electrically connecting said inner end portion of each of said two other bars to said inner end portion of only one of said bars in said respective pair, and electric lead wires selectively connected to said inner end portions of only the other of said bars in each of said pairs and projecting therefrom.

2. An antenna as defined in claim 1 and which includes conductor means directly interconnecting said outer end portions of said other bars.

3. An antenna comprising dielectric supporting means, four elongated substantially straight bars, each of said bars having an inner end portion and outer end portion and being disposed in spaced relation to each other with said inner end portion mounted on said supporting means and said outer end portion projecting outwardly from said supporting means, said bars projecting from said supporting means in two substantially oppositely projecting pairs, each of said pairs comprising an upper bar and a lower bar disposed in vertically spaced substantially parallel relation to each other, two substantially U- shaped bars, each of said U-shaped bars having two elongated legs and being slidably mounted on a respective one of said pairs of bars in outwardly projecting relation thereto and with each of said legs mounted on a respective bar of said pair for movement longitudinally thereof, two other elongated bars substantially straight throughout their length, each of said other bars having an inner end portion and an outer end portion and being disposed in spaced relation to the other of said other bars and said four bars with said inner end portion mounted on said supporting means and said outer end portion projecting outwardly from said supporting means, each of said two other bars being disposed between said upper and lower bars in a respective one of said pairs and being disposed at a horizontal acute angle to a respective one of said pairs, means selectively electrically connecting said inner end portion of each of said two other bars to said inner end portion of only one of said bars in said respective pair, and electric lead wires connected to the inner end portion of said first mentioned bars.

4. An antenna as defined in claim 3 and in which the acute angle at which each of said other bars is disposed relative to said respective one of said pairs is not substantially less than ten degrees and not substantially more than thirty degrees.

5. An antenna comprising dielectric supporting means, four elongated substantially straight bars, each of said bars having an inner end portion and outer end portion and being disposed in spaced relation to each other with said inner end portion mounted on said supporting means and said outer end portion projecting outwardly from said supporting means, said bars projecting from said supporting means in two substantially oppositely projecting pairs, each of said pairs comprising an upper bar and a lower bar disposed in vertically spaced substantially parallel relation to each other, two slides, each of said slides extending between and electrically interconnecting the bars in a respective one of said pairs and being movable longitudinally thereof, two other elongated bars having inner end portions and outer end portions, said other bars being mounted at their inner end portions on said supporting means in spaced relation to each other and having their outer end portions projecting horizontally away from said first mentioned bars, electrical conductor means selectively connecting the inner end portion of each of said other bars to the inner end portion of a respective one of said bars in a respective one of said pairs, other electrical conductor means mounted on and directly interconnecting said outer end portions of said two other bars, and means connected to said first mentioned bars for connecting the latter to a receiver.

6. An antenna as defined in claim 5 and in which said other electrical conductor means comprises an elongated conductor consisting of material of substantially smaller cross-sectional area than said other bars.

7. An antenna as defined in claim 5 and in which said other electrical conductor means comprises a tension coil spring mounted on and extending in tension between said outer end portions of said other bars.

8. An antenna comprising dielectric supporting means, two reversely bent bars, each bar having two elongated legs disposed in spaced relation to each other at one end to form an open end portion and connected together at the other end to form a closed end portion, said bars being mounted on said supporting means with said open end portions disposed in spaced relation to each other and said closed end portions projecting away from each other, said one end of each leg in each of said pairs being electrically connected to said one end of the other said leg in said pair only through said closed end portion of said pair. two elongated bars having inner end portions mounted on said supporting means in spaced relation to each other and having outer end portions projecting horizontally away from said first mentioned bars, electrical conductor means selectively connecting said inner end portion of each of said elongated bars to said inner end portion of a respective one of said two legs of a respective one of said bent bars, electrical conductor means mounted on and directly interconnecting said outer end portions of said elongated bars, and electrical conductor means connected to said bent bars for connecting the latter to a receiver.

JOHN HLIVJAK.

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

UNITED STATES PATENTS Number Name Date 1,581,123 Mackenzie Apr. 20, 1926 2,258,406 Carter Oct. 7, 1941 2,494,665 Marshall Jan. 17, 1950 2,495,579 Ferris et al. Jan. 24, 1950 2,614,220 Doerner Oct. 14, 1952

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