US2366634A - Antenna - Google Patents

Description

S. LUDWIG Jam. 2, 1945.

5 Sheets-Sheet 2 ATTORNEYS S. LUDWIG Jam 2, 1945.`

ANTENNA Filed July 22, 1941 3 Sheets-Sheet 3 INVENTOR SIDNEY LUDWIG ATTORNEYS roc. ff. el

Lw, Utili Patented Jan. 2, 1945 ANTENNA Sidney Ludwig, Cleveland, Ohio, assignor to The Ward Products Corporation, Cleveland, Ohio, a corporation of Ohio Application July 22, 1941, Serial No. 403,521

(Cl. Z50-33) 9 Claims.

This invention relates to improvements in radio antennas, and, more particularly, to telescopic antennas employed on automobiles or other vehicles.

Heretofore, the Well-known telescopic antennas comprised of telescoping assemblies of metal tubes or tubes and rods have been found to be themost satisfactory antennas for radios installed in automobiles or other vehicles. Such antennas were usually assemblies of chromeplated brass or other electrically conductive metal tubes mounted on the side cowl of automobiles, for example, and connected to the radio receiving set through an insulated stanchion and grounded cable. It was considered essential that such telescopic assemblies be of electrically conductive material in order to pick up radio-frequency signals. While such metallic tubular assemblies were satisfactory, they were not free from objectionable features, as will be pointed out below.

An object of my invention is to provide a telescopic antenna comprising an assembly of nonmetallic, non-conducting tubes, such as, for example, tubes of organic materials generically known as plastics The advantages of employing plastic tubes in a telescopic antenna are manifold. First, such plastic tubes are much cheaper and lighter than the brass or like metal tubes universally employed heretofore. Second, such plastic tubes will provide the necessary strength and rigidity in a telescopic antenna and permit the function of picking up radio-frequency signals to be performed by a line metal strip or Wire carried Within the tube, thus reducing the amount of metal required in the antenna to a minimum, a fraction of a percent of the metal required heretofore.

Another object of this invention is to effectively eliminate atmospheric corrosion. Heretofore, the outer surfaces of telescopic antennas were usually chrome-plated to reduce corrosion, Due to the fact that antennas on automobiles or boats, for example, were subjected to extremely corrosive atmospheric conditions, such plating had to be heavy and was, consequently, expensive. Furthermore, such plating was not permanent. In my antenna the problem of atmospheric corrosion is substantially eliminated. Furthermore, my antenna may be made in an almost infinite range of colors to match, harmonize, or contrast with the color of the vehicle on which it is mounted.

A further object of my invention is to eliminate the problem of lubrication between the telescoping sections of antennas. In the metal antennas employed heretofore, it was necessary to maintain a lm of lubricant on the movable sections of the antenna. With my plastic antenna, no such lubrication is necessary. A still further advantage of my antenna is that it is more flexible and less likely to be deformed or broken than the metal antennas employed heretofore.

My telescopic antenna may comprise a telescopic assembly of tubes either having a thin conductor carried by each tube with means for establishing contact between the separate conductors or having a single conductor or cable carried by the uppermost tube and extending through the lower tubes, preferably to a means for taking up the single continuous conductor when the antenna is collapsed.

It is a still further object of this invention, therefore, to Provide take-up means for a telescopic antenna having a single cable extending through the tubular members of the antenna assembly. An advantage of my antenna with a single continuous cable extending through the telescopic antenna tubes is that the problem of establishing electrical contact. and, therefore, the problem of noise caused by a loose contact between sections is eliminated. This also simplies the construction and assembly of the antenna tubes and may offset the additional cost of the take-up means.

Another advantage of my single continuous cable type of antenna is that it may be provided with a driven take-up reel, thus allowing the antenna to be extended or telescoped by remote control; that is, the antenna may be a so-called automatic" antenna. In such automatic antennas, however, it is substantially essential that the antenna may also be extended or telescoped manually. Otherwise, the automatic" mechanism may be jammed or broken by service men, car washers, or children, for example. It is yet another object of this invention to provide a remotely controlled automatic antenna mechanism which will not bind and which will permit the telescopic antenna. to be actuatedmanually without jamming the automatic mechanism.

Other objects and advantages of this invention will be apparent from the following specication, claims, and drawings, in which:

Fig. 1 is an elevation of one embodiment of my telescopic antenna fully extruded but having portions broken away for purposes of illustration.

Fig. 2 is an enlarged fragmentary longitudinal section taken at a joint of the antenna shown in Fig. 1.

Fig. 3 is a further enlarged cross-section taken along the line 3-3 of Fig. 2.

Fig. 4 is an enlarged fragmentary longitudinal section taken at the stanchions of the antenna shown in Fig. l and shortened for purposes f illustration.

Fig. 5 is an elevation of another embodiment of my telescopic antenna fully extended but having portions broken away for purposes of illustration.

Fig. 6 is an enlarged section taken along the line 6-6 of Fig. 5.

Fig. '7 is an enlarged detail side elevation of the reel case shown in Fig. 5.

Fig. 8 is an enlarged section, partly curved, taken along the line B-Bin Fig. 'l and to show the take-up assembly.

Fig. 9 is a detailed elevation of the reel employed in the embodiment illustrated in Fig. 5.

In the drawings, in which like reference characters refer to like parts, Figs. 1 to 4 show a preferred embodiment of my manually telescopic antenna in which a conductor is carried by each tube in the telescopic assembly and means are provided to establish electrical contact between the several sections. In Fig. 1, my telescopic antenna assembly I0 is comprised of a xed outer tube I2 and an inner tube I4 telescopically slidable in the outer tube I2.

Preferably all of the tubes in my antenna Ill are of non-metallic non-conducting organic plastic material such as, for example, extruded tubes of polystyrene, cellulose acetate, cellulose nitrate,

ethyl cellulose, polymerized vinyl resins, polymerized methacrylate resins, phenolic condensation products, hard rubber, or any other like plastic material. While such tubes are preferably of such extruded plastic materials having incorporated pigments and/or dyes, the tubes may be built up, as by spiral winding, not only from strips of such plastic materials but also of other nonmetallic non-conducting materials such as vulcanized fiber, paper or fabric impregnated with thermo-setting resins, such as alcohol modified urea-formaldehyde resin, for example, or like materials capable of being formed into comparatively thin-walled small diameter tubes having appreciable rigidity without being especially brittle. The foregoing materials are set forth by way of example and not by way of limitation; in each material the dimensions of the tubes maybe varied to meet the expected wind and shock loads to which the antennas may be subjected, In the case of plastics, the preferred material, the amount of plasticizer may be varied to give the tubes the required stiifness and flexibility. Insofar as the operativeness of an antenna made according to this invention is concerned, glass tubing may be used, although such tubing would not generally be practical because of its low shock strength. Plastic materials, such as cellulose acetate, polystyrene, polyvinyl resin, andthe like, are also preferred because they may be obtained in the form of smooth surfaced tubes which will permit one to slide within the other without lubricants and yet with suflicient friction to main` tain itself in its adjusted position under normal conditions; furthermore, such plastic tubes are strong enough to remain fairly straight under ordinary wind loads but, when struck or intentionally exed, they will not break easily but will return to their normally straight condition without permanent deformation.

As shown in Figs. 1 to 3, the tube I2 is provided with an internal conductor I5 extending substantially the length of the tube I2 and being either secured to the wall of the tube I2 or of sufficient rigidity so that it will not collapse within the tube. In the embodiment disclosed, the conductor I5 is a narrow strip of spring metal, such as phosphor-bronze, curved to t the inner wall of the tube I2 and to increase the rigidity of the conductor. The bore of the fixed tube I2 is made large enough to carry the conductor I5 and also to accommodate the telescoping tube I4. However, the upper end of the tube I2 is preferably provided with a narrower neck I6, the bore of which engages the outer surface of the telescoping tube I4 with a close sliding lit. A collar or ferrule I'I may be employed to reinforce the neck I6, which serves as a bearing for the tube I4.

The tube I4 is also provided with an internal conductor IB similar to the internal conductor I5. In order to establish electrical contact between the conductor I8 and the conductor I5, the telescoping tube I4 carries a contact shoe I9 to which the conductor I8 is electrically connected. In the embodiment disclosed, the contact shoe I9 comprises a short sleeve secured to the lower end of the tube I4 and having an expanded split skirt which bears against the inner wall of the tube I2 and the conductor I5. Thus, the portion of the radio signal which is picked up by the conductor I8 is conducted tothe conductor I5 through the contact shoe I9 in whatever position the tube I4 is telescoped within the tube I2. By making the contact shoe in the form of a sleeve having a substantially continuous surface, rather than the customary flexible finger, rotation of the tube I4 with respect to the tube I2 will not tend to bend or break the shoe or interrupt Contact with the conductor I5.` The friction between the contact shoe and the tube I2 augments the friction betweenthe collar I6 and the tube I4, so that the antenna will remain in its adjusted position. By having the shoe I9 ttedv on the outside of the tube I4, as shown, it also acts as a stop to prevent the tube I4 from being withdrawn from the tube I2. In this connection, it should be noted that the neck IB is preferably provided with a flat shoulder so that the shoe will not wedge or jam when it engages the neck I6.

For simplicity of illustration, the antenna` I Il has been shown as a two-section antenna. Usually, however, the antenna. will be comprised of an assembly of three, and perhaps more, telescopic tubes. In case it is desired to make a three-section antenna, for example, a smaller tube will simply be slidably mounted in the tube I4 in the manner in which the tube I4 is mounted in the tube I2, and the slidable contact between the conductor carried by the smaller tube and the conductor I8 may be the same as the contact between the conductor I8 `and the conductor I5. By simply repeating the joint, as shown in Figs. 2 and 3, the antenna I0 may be made of any convenient number of telescopic sections.

One manner of mounting the antenna I0 and connecting it to the lead-in of the radio set is best shown in Fig. 4, wherein 20 represents a Wall of the vehicle on which the antenna is mounted, as, for example, the side cowl wall of an automobile. The antenna is mounted in two more or less conventional stanchions 2l and 22, each comprised of the intertted pad 23, hollow insulator 24 and cap 25 mounted externally of the Wall 20. The antenna I0 passes through the caps 25 and is engaged thereagainst by the ring of the bolt 26, which is, in turn, secured in the hollow `insulator 24 by the nut 21. The bolts 26 extend iii" through the wall 26 into the shield cans 28 provided with the insulators 29 which insulate the bolts 26 from the wall 20. By suitable securing means (not shown) on the ends of the bolts 26 within the shield cans 28, the stanchions 2| and 22 are secured to the outer surface of the wall 26 and the shield cans 28 are grounded to the inner surface of the wall 20. Although the bolt 26 in the upper stanchion 2I is not connected to the conductor I because it engages the non-conducting tube I2, the bolt 26 is in inductive relationship with the conductor I5, and it is, therefore, preferable to insulate and shield the bolt 26 in the stanchion 2 I.

In order to provide a direct electrical connection between the conductors of the antenna IIl and the radio set lead-in 30, the bottom of the tube I2 is tted on a conductive plug 3| which is connected to the conductor I5, thereby leading the signals picked up by the conductor I5 to the outside of the non-conducting tube I 2. The plug 3| is both mechanically and electrically engaged by the bolt 26 of the lower stanchion 22, which bolt 26 is connected within the lower shield can 28 to the conventional shielded lead-in cable 36. This double stanchion mounting is shown by way of illustration only. Because the plug 3l, or other suitable means, may be used to serve as an electrical lead from the internal conductor I5 to a point outside the fixed tube I2, any other type of mounting suitable for a manually extensible antenna may be employed, as, the type of antenna mounting known commercially as a Flex-angle mounting, shown in my copending application, Serial No. 314,253, U. S. Patent No. 2,251,889, granted August 5, 1941, or the type of concealed mounting known commercially as a Bi-flex mounting, shown in my copending application, Serial No. 383,600, U. S. Patent No. 2,252,671, granted August 12, 1941.

In operation, the tubes I2, I4, et cetera, are set at the desired length permitted by the telescoping assembly. The internal conductors I5, I8, et cetera, in the antenna I0 pick up radiofrequency signals which, as will now be appreciated, are not insulated from the conductors by the non-conducting telescopic tubes, I2, I4, et cetera. Such signals are led into the radio set through the plug 3 I, bolt 26 of the lower stanchion 22, and the lead-in cable 30.

Single conductor telescopic antenna In the foregoing description of a telescopic antenna in which the non-conducting telescopic antenna tubes are each provided with a conductor, the several conductors are connected by sliding contact means. Because the sliding contact means may, unless carefully made, eventually become loose and cause noisy reception, I have provided a telescopic antenna having a single continuous conductor, as shown in Fig. 5, which eliminates the problem of maintaining contact between the telescopic sections of the antenna. As shown in Fig. 5, the antenna 40 is comprised of a plurality of telescopic tubes 42 and 44 of non-metallic non-conducting material similar to the tubes I2 and I4 of the antenna I0. Because, as will be apparent, no problem of maintaining electrical contact between the sections of the antenna 40 is present, any suitable type of frictional joint between the telescopic tubes 42, 44, et cetera, may be employed. As shown in Fig. 5, the joint between the tubes 42 and 44 is the ferrule-less type, such as disclosed in my copending application Serial No. 408,486. `Of course, a ferruled joint` may be employed, as shown in Fig. `1. In the event the telescopic joint between the tubes does not provide sufcient friction to maintain the tubes in their adjusted telescopic position, friction shoes may be carried on the bottom of the telescoping tube, similar to the shoe I9 shown in Fig. 2, for example.

In the antenna 40, a single continuous conductor 45, such as a wire or tape, is carried by the inner telescoping tube 44 and extends through the outer xed tube 42 and its mounting 50, which secures the antenna 40 to the vehicle wall 5I The particular mounting 50 shown in Fig. 5, is a Biflex type of mounting described in detail in my copending application Serimgwllm From the open lower end of the tube 42, the con uc or 45 runs to a take-up device 60, provided with a lead-in sleeve 65, which is in electrical contact with the conductor wire 45. To insure an electrical contact between the conductor wire 45 and the lead-in sleeve, a spring contact nger (not shown) may be provided on the sleeve. The leadin sleeve 65 is provided with a lead-in pin 66 adapted to be connected by any conventional lead-cable to the radio set.

In operation, the antenna 40 is set at the desired length within the range permitted by the telescoping tubes 42 and 44. As the antenna is adjusted from its fully telescoped length to its maximum length, the conductor wire 45 moves into the antenna 40 from the take-up device 60. Radio frequency signals picked up by the conductor wire 65 are conducted to the radio set leadin cable through the lead-in sleeve 65 and lead-in pin 66. Thus, no sliding contact is required between the telescoping sections of the antenna.

The take-up device for the Wire 45 may be of any suitable type, preferably the so-called automatic type 60, described at length below.

Automatic antenna My antenna 40, having a continuous wire cable 45 extending the length thereof, may be operated as an automatic antenna, that is, an antenna Y which may be raised or lowered by remote control by means of the automatic take-up device 60, as shown in detail in Figs. 5 to 9. In such an automatic antenna, the wire cable 45, while ilexible, should be stiff enough to have spring characteristics and should be stiff enough so that it will not be crushed or deformed within the bores of the antenna tubes by any longitudinally applied force great enough to extend the antenna 46 from its telescoped position.

The automatic take-up device 60 is comprised of a grounded metallic shielding case 6I and removably secured case cover 62, the case 6I being preferably secured to the mounting 50 and electrically connected to the grounded members thereof. Within the case is a xed drum cap 63 and rotatable drum 64. If the drum cap 63 and drum 64 are not made of non-conducting material as shown, they should be insulated from the grounded case 6I and cover 62.

The insulated lead-in sleeve 65 is carried by the case 6I, so that the bore of the lead-in sleeve is aligned with the bores of the telescopic tubes in the antenna 40. The lead-in sleeve 65 is electrically connected with the antenna 40 and is provided with the offset lead-in pin 66 adapted to be connected to a conventional shielded lead-in cable through the opening 61 in the grounded case cover 62.

As shown in Fig. 6, the cover 62 carries a bearing 68 for the drum shaft 6,9 to which the drum search Stoom 64 is fixed. Suitable means, such as the drum shaft shim 10, spaces the drum 64 from the cover 62. The periphery of the drum 64 is provided with a deep annular spooling slot 1| to receive the wire 45. The radial width of the slot is greater than one diameter but preferably less than two diameters of the wire 45 to allow ample clearance for free axial movement of the wire within the slot while preventing one turn of wire from passing over another turn to snarl the wire in the slot 1|. The wire 45 is laid and secured in the bottom of the spooling slot 1I, as, for example, by inserting the bent tip 46 of the wire 45 in the axially extending socket 12 and pinning the wire against the bottom of the slot by the pin 13 extending radially through the slot at a point spaced from the socket 12. By so laying and securing the wire 45 in the bottom of the spooling slot 1I, the resilience of the wire will tend to draw the wire toward the bottom of the slot. Thus, as successive turns of the wire are wound into the spooling slot, the wire will be self-laying within the spooling slot due to the tendency of the successive turns of the Wire to move toward the bottom of the slot. The length of the wire 45 is preferably selected so that at least one turn will remain in the slot 1| when the antenna 40 is fully extended.

The fixed drum cap 63 is provided with a circular face concentric with and axially opposite the open end of the annular spooling slot 1|. A clearance is provided between the face 15 and the drum 64, the clearance being large enough so that there will be no tendency of the rotated drum to rub or bind and small enough so that the wire 45 cannot fall into the clearance and jam the drum. This clearance will be main tained by the thrust of the wire remaining in the slot 1| when the antenna 40 is fully extended, as will be pointed out hereafter. To insure the clearance, however, the case 6| may be provided with a boss, for example, which the inner end of the drum shaft will engage before the drum can. engage the face 15.

The drum cap 63 is provided with a slot 16 to receive the lead-in sleeve 65 so that the axis of the lead-in sleeve will be maintained tangent to the surface of a cylinder defined by the center of the spooling slot 1|, said cylinder being hereinafter referred to as the cylinder of feed. The lead-in sleeve preferably ends at the point of tangency between the cylinder of feed and the axis of the lead-in sleeve. The cylinder of feed may also be defined as a theoretical surface on which the axis of the wire 45 would lie when wound into a helix having a slight clearance with the actual surface of the drum 64.

Where the axis of the lead-in sleeve is perpendicular to a plane passing through the axis of the cylinder of feed, as in the embodiment disclosed, a means should be provided for feeding the wire 45 in a helical direction into the spooling slot 1|. In the preferred embodiment dis closed, such means is provided by the arcuate helical feed slot 11. The feed slot 11 is preferably cut so that it is wide enough to provide no more than a good running t for the wire 45 and so that its center line lies on the surface of the cylinder of feed. The pitch of the feed slot 11 may be cut at any desired helical angle soy that the wire 45 will not tend to kink or bind in the lead-in sleeve 65 as it moves in the feed slot 11. Preferably, the pitch of the feed slot 11 is also greater than the natural pitch of the length of wire remaining in the spooling slot 1| when the antenna 4U is fully extended. Thus, the slot 11 will force the wire 45 across the clearance between the drum 64 and the drum cap face 15 into the spooling slot 1 maintaining a thrust on the drum 64 away from the drum cap face 15. The helical feed slot 11 will, of course, tend to feed the wire 45 toward the bottom of the spooling slot 1|, thus aiding the pin 13 in causing the wire to be self-laying in the slot 45. Furthermore, by having a pitch greater than the pitch of the wire in the slot 1|, the feed slot 11 will prevent the wire from snubbing in the slot 1I.

As shown in Fig. 6, the drum shaft 69 is connected to one end of a flexible rotatable shaft 8U, as, for example, by means of the tongue and groove chuck 8|. The other end of the flexible shaft is provided with a hand knob 82 mounted at a remote control point, such as, for example, the dash board 83 of an automobile. Thus, by turning the knob 83 the drum 64 will be rotated and the wire 45 will be wound or unwound in the spooling slot 1 I.

Operation of the automatic antenna While the operation of my automatic antenna 1s substantially apparent from the foregoing description of the tal e-up device, its operation may be summarized as follows: With the telescopic antenna fully extended, as shown in Fig. 5, the wire 45 extends throughout the length of the bore of the extended antenna, through the mounting 5U, and into the lead-in sleeve 65, from which the wire is directed in a helical direction by the feed slot 11 into the spooling slot 1|. With approximately one turn wound in the spooling slot, as shown in Figs. 6 and 8, the end 46 of the wire 45 is fastened to the bottom of the spooling slot. By turning the drum 64 to draw the wire into the spooling slot, the telescoping antenna tube 44 is drawn into the fixed antenna tube 42 until the antenna 40 is fully telescoped. When the antenna is fully telescoped, the wire 45 will be wound in a helix in the spooling slot 1| of the drum 64, as shown in Fig. 9, due to the function of the pin 13 and the feeding slot 11 which render the wire 45 self-laying and prevent snubbing of the wire within the spooling slot. To extend the telescoped antenna, the drum 64 is rotated in the opposite direction, feeding the Wire 45 out of the spooling slot in the feed slot and 1eadin sleeve to the bore of the antenna 40, where the wire exerts a longitudinal force on the telescoping tube 44 to force the tube 44 out of the xed tube 42.

Because the rotating drum 64 does not bind against the fixed drum cap 63 and because the wire 45 is wound and unwound in the spooling slot 1| in a self-laying and non-snubbing manner, the antenna 4U may be telescoped or extended by manually moving the telescoping tube 44 in or out of the xed tube 42 by allowing the drum shaft drive to be rotatable when it is not being driven. Thus, my take-up device 6D cannot be jammed or broken when unauthorized persons manually extend or telescope the antenna 40.

It is apparent from the foregoing that the embodiments disclosed have been set forth by way of example, consequently may be modied, either in whole or in part, without departing from the spirit and scope of my invention. My invention, therefore, is not limited to the specific embodiments disclosed but by the appended claims.

What is claimed is:

1. As an article of manufacture, a radio ani. iii iii Eri tenna comprising a telescopic assembly of a plurality of tubes of non-metallic, non-conducting material, means constituting an internal radiofrequency pick-up conductor extending substantially the length of the bore of the telescopic tube assembly, and means for establishing an electrical connection between the internal electrical conductor and a radio set.

2. A telescopic radio antenna comprising a fixed tube of non-conducting material, a metallic radio frequency pick-up conductor carried by said xed tube, a telescoping tube slidable in and out of the bore of the fixed tube, a metallic conductor carried by the telescoping tube, and means for establishing a sliding electrical contact between the conductors carried by the fixed tube and the telescoping tube.

3. In a telescopic antenna, a first tube of nonconducting plastic material, an internal metallic conductor strip extending the length of the bore of the rst tube, a second tube of non-conducting plastic material telescopically assembled with said first tube, a second internal metallic conductor strip carried by said second tube, and means for establishing a sliding electrical contact between the internal conductors in said rst and second tubes.

4. A telescopic radio antenna comprising a telescopic assembly of a plurality of tubes of nonconducting plastic material, a conductor comprising a strip of metal on the internal wall of each of the tubes and extending substantially the lengths thereof, a metallic plug in the open end of the outer tube of the assembly and electrically connected with the metal strip carried by the outer tube, an expansible contact shoe carried by the inner end of the next inner tube of the assembly, said contact shoe maintaining a slidable electrical Contact with the conductor strip of the outer tube and being electrically connected to the conductor strip of the next inner tube, and means engaging the metal plug to support the telescopic assembly and to establish an electrical connection between the plug and a lead-in cable of a radio set.

5. A telescopic radio antenna comprising a telescopic assembly of concentric tubes of nonconducting plastic material, a single continuous metallic conductor carried by an inner tube of the assembly and having a length substantially equal to the extended length of the telescopic assembly, and means for establishing an electrical connection between the single continuous metallic conductor and a radio set.

6. A telescopic radio antenna comprising a telescopic assembly of a plurality of concentric tubes of non-conducting plastic material, a single continuous internal conductor of spring metal,

Search Room having a length at least equal to the extended length of the telescopic assembly, attached at one end to an inner tube of the assembly so that it will extend substantially the length of the assembly and being preformed at its other end so that it will contract when no tension is applied to the end attached to the inner tube of the assembly, and means for establishing electrical contact between the single continuous internal conductor and a radio set.

7. A telescopic radio antenna comprising a telescopic assembly of concentric tubes of nonconducting plastic material, a single resilient internal radio-frequency pick-up conductor having a length greater than the extended length of the telescopic assembly, a take-up mechanism, one end of said conductor being secured to an inner tube of the assembly and the other end being secured in the take-up mechanism whereby said take-up mechanism will permit the internal conductor to be drawn in and out of the assembly as the assembly is extended or telescoped, and means for establishing an electrical connection between the internal conductor and a radio set.

8. A telescopic radio antenna as defined in claim '7 in which the internal conductor comprises a wire having spring characteristics and the take-up mechanism comprises a case, a drum rotatable within said case, said conductor being secured to said drum, and means to wind and unwind said conductor on said drum.

9. A telescopic radio antenna as defined in claim 'I in which the internal conductor comprises a wire having spring characteristics, the take-up mechanism comprises a case, a case cover, a bearing carried by said case cover, a drum shaft rotatable in said bearing, a drum carried by said shaft, said drum having an annular spooling slot cut therein, a fixed drum cap, means securing the end of said wire against the bottom of said spooling slot to cause said wire to be selflaying within said spooling slot, a lead-in sleeve through which said wire passes, a drum cap axially spaced from said drum, said drum cap having a slot receiving said lead-in sleeve and maintaining said lead-in sleeve so that its axis is tangent to the cylinder of feed of said spooling slot in said drum, means in said drum cap to feed the wire from said lead-in sleeve into the said spooling slot in a helical direction, and means controlled from a remote point for winding and unwinding said wire in said spooling slot to telescope and extend the telescopic antenna, and in which the means for establishing electrical contact between said wire and a radio set includes a lead-in pin carried by the Said lead-in sleeve.

SIDNEY LUDWIG.

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