Abstract:
The present invention is directed to an antenna system comprising two rigid portions, an electrical conductor located between the two rigid portions, and a connector that extends between the two rigid portions and: (a) allows the position of one of the rigid portions relative to the other rigid portion to be altered when a force is applied to one of the rigid portions, such as when one of the rigid portions encounters an obstacle, and (b) maintains the altered position until a subsequent force is applied. In one embodiment, the connector comprises a ball-and-socket joint with the spring force produced by the socket causing sufficient frictional force between the ball and socket so that the position relationship of the ball to the socket is maintained when only gravity is being applied to the rigid portions and the connector but allowing the positional relationship to be altered when an additional force is applied. In another embodiment, the connector is comprised of multiple ball-and-socket links that each provide a limited angular range of motion and cumulatively allow an angular range of motion that is the sum of the limited angular ranges of motion associated each of the links.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an antenna system and, more specifically, to an antenna system in which the relative positions of two rigid portions of the system can be adjusted. 
     BACKGROUND OF THE INVENTION 
     Generally, a radio system is comprised of a transmitter and/or receiver and an antenna system that is used to receive radio signals that are provided to a receiver and/or transmit radio signals produced by a transmitter. For convenience, the portion of a radio system comprised of a transmitter and/or receiver will hereinafter be referred to as a transceiver. In many situations, the relative positions of elements of the antenna system are static. For instance, commercial radio stations typically employ an antenna system that is situated on a geographical high point in the broadcast area. The positions of the elements of such an antenna system are substantially static. However, in many other situations, it is desirable to allow the relative positions of the elements of an antenna system to be altered to prevent damage to elements of the antenna system that could render the system inoperative. This is particularly so in portable radio system applications. For instance, it is not uncommon for a portion of an antenna system that extends away from a vehicle or a portion of an antenna system that extends away from the body of a foot soldier to encounter an obstacle that could damage the antenna system. 
     There are at least two approaches to allowing the relative relationships of elements of an antenna system to be altered. The first approach employs a spring that is interposed between two portions of an antenna system and, when one portion of the antenna system is engaged by a force, allows the relative positions of the two portions to be altered. When the position altering force is subsequently removed, the energy stored in the spring is used to return the portions of the antenna system to their original positions. The other approach is to provide a connector between the two portions of the antenna system that allows the relative positions of the two portions to be altered when one portion is engaged by a force. However, in this approach, the connector does not store any energy. So, when the force is no longer being applied to the engaged portion of the antenna system, the two portions of the antenna system do not return to their original positions but remain in whatever new relative positions resulted from the application of the force. A new force must be applied to return the portions of the antenna system to their original positions or to a different position from the original position or position resulting from the application of the force. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an antenna system that allows the relative positions of two portions of the system to be altered in response to a force being applied to at least one of the portions and that preserves the new relative positions after the application of the force is terminated. 
     In one embodiment, the antenna system is comprised of first and second substantially rigid portions, a flexible electrical conductor that extends between the portions, and a connector that extends from the first portion to the second portion. The connector maintains the positional relationship between two rigid portions when the only torque/force being applied is gravity but allows the positional relationship between the two rigid portions to be altered upon the application of an additional force. The connector includes a ball and a socket that are joined to one another so as to form a ball-and-socket joint. The joint maintains the positional relationship of the ball and socket to one another, as well as other elements of the system, provided the only force/torque being applied to the system is attributable to gravity. This positional relationship is maintained due to the frictional force between the interior surface of the socket and the portion of the exterior surface of the ball that is in engagement with the interior surface of the socket. This frictional force is achieved by establishing an interference fit between the ball and the socket. The joint, however, also needs to allow the relative positions of the two rigid portions of the system to be altered. 
     In one embodiment, the interference fit needs to: (a) maintain the relative positions of the two rigid portions when the only force/torque being applied to the system is attributable to gravity but allow the relative positions to be altered when an additional force/torque is applied, (b) be durable and/or abrasion resistant so that the ability to change the relative positions of the rigid portions can be maintained over numerous cycles, and (c) is a dielectric that has little, if any, effect upon the operation of active elements in the system. In one embodiment, this interference fit in this embodiment is achieved by employing a ball and socket in which the interior surface of the socket and the exterior surface of the ball that is capable of coming into contact with the interior surface of the socket are each realized by employing an ultra-high-molecular-weight polyethylene (UHMWPE), such as Lennite™ or Nylatron™ polyethylene. The socket and/or the ball can be produced by molding UHMWPE or machining a block of UHMWPE. 
     In another embodiment, the ball and socket of the joint define a passageway for accommodating at least a portion of the flexible electrical conductor located between the two rigid portions. The ball and socket each define a portion of the passageway. In a particular embodiment, the portion of the passageway defined by the ball includes a frusto-conical portion that, in combination with the portion of the passageway defined by the socket, allows the conductor to flex over a distance when the relative positions of the ball and socket change. This prevents the conductor from being bent around a sharp corner that could damage the conductor and/or unduly fatigue the conductor. 
     Another embodiment of the antenna system employs a connector that is comprised of several links, two end-links that each engage one of the rigid portions of the antenna and one or more intermediate links that are located between the end links. The end links can each be a ball without a socket (hereinafter referred to as a “ball end link”) or a socket without a ball (hereinafter referred to as a “socket end link”). The intermediate link or links are each a rigid structure that is one of a ball-and-socket link, a socket-and-socket link, or a ball-and-ball link. In one embodiment, each of the end links is a ball end link that is suitable for establishing a ball-and-socket joint with an intermediate link that includes a socket. For example, a single socket-and-socket link can be used to link the ball end links to one another. In this case, two ball-and-socket joints are established, i.e., one ball-and-socket joint is established between one of the ball end links and one of the sockets of the socket-and-socket link and the other ball-and-socket joint is established between the other ball end link and the other socket of the socket-and-socket link. In another embodiment, one end link is a ball end link that is suitable for establishing a ball-and-socket joint with an intermediate link that includes a socket and the other end link is a socket end link that is suitable for establishing a ball-and-socket joint with an intermediate link that includes a ball. In this embodiment, a ball-and-socket link can be used to engage the two end links and, in so doing, establish two ball-and-socket joints. It should be appreciated that there can be more than one intermediate link. For instance, two ball-and-socket links can be engaged to one another such that the ball of one of the links engages the socket of the other link. In any event, combinations of end links and intermediate links can be used to establish one or more ball-and-socket joints that allow for the repositioning of the rigid portions of the antenna system. Further, because each ball-and-socket joint has a limited range of motion, a connector that employs a greater number of links will provide for greater flexibility in the positioning of the rigid portions of the system to one another. For example, if the range of motion of each ball-and-socket joint is limited to 22.5°, a connector with two ball-and-socket joints will limit that range over which the two rigid portions can be positioned relative to one another to 45°. However, a connector with four such ball-and-socket joints will allow the two rigid portions to move within a 90° range of one another, if needed or desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a radio and an embodiment of an antenna system according to the present invention; 
         FIG. 2  is a cross-sectional view of the antenna system illustrated in  FIG. 1 ; 
         FIG. 3  is an exploded view of the connector portion of the antenna system shown in  FIG. 1  without any electrically active antenna elements; 
         FIG. 4A  illustrates the open-ended ball structure of a ball end link; 
         FIG. 4B  is a cross-sectional view of a ball end link comprised of an open-ended plug and the open-ended ball structure shown in  FIG. 4A ; 
         FIGS. 5A and 5B  respectively illustrate a ball-and-socket link and a cross-sectional view of the ball-and-socket link; 
         FIGS. 6A and 6B  respectively illustrate a socket-and-socket link and a cross-sectional view of the socket-and-socket link; 
         FIG. 7  illustrates the five ball-and-socket joints associated with the connector shown in  FIG. 1 ; 
         FIG. 8  illustrates a cross-section of a ball-and-socket joint established using two ball-and-socket links; 
         FIGS. 9A and 9B  respectively illustrate a socket end link and a cross-sectional view of the socket end link; 
         FIGS. 10A and 10B  respectively illustrate a ball-and-ball link and a cross-sectional view of the ball-and-ball link; 
         FIGS. 11A-11C  illustrates the antenna system of  FIG. 1  associated with a foot soldier and the response of the antenna system when one of the rigid portions of the antenna system is engaged by an overhanging obstacle in the foot soldier&#39;s path. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a radio system is comprised of a radio  20  and an antenna system that is connected to the radio  20  and includes: (a) an antenna or antennas that are each capable of radiating an electro-magnetic signal and/or receiving a radiated electro-magnetic signal and (b) the structure for supporting and/or positioning and/or protecting the antenna or antennas. 
     With continuing reference to  FIG. 1 , an embodiment of an antenna system that maintains the relative positions of two rigid elements of the system when the only force/torque acting on the system is attributable to gravity but also allows the relative positions of the two rigid members to be altered by the application of an additional force/torque and remain in the altered position upon the termination of the addition force, hereinafter antenna system  22 , is described. The antenna system  22  is used in conjunction with a radio  20 . The radio  20  with which the antenna system  22  is used can be only a radio receiver, only a radio transmitter, or a radio transmitter and receiver (i.e., a transceiver). In the illustrated embodiment, the radio  20  and the antenna system  22  are separated from one another but connected to one another by an electrical conductor  24 . The electrical conductor  24  can be a part of the radio  20  and include a connector that allows the remainder of the conductor to be connected to the antenna system  22 , a part of the antenna system  22  and include a connector that allows the remainder of the conductor to be connected to the radio  20 , or a separate part with connectors that allow the conductor to be connected to the radio  20  and to the antenna system  22 . 
     With reference to  FIGS. 1 and 2 , the antenna system  22  is comprised of: (a) a first rigid portion  26 , (b) a second rigid portion  28 , and (c) a connector  30  for connecting the first rigid portion  26  and the second rigid portion  28  to one another. The first rigid portion  26  is comprised of a base plate  32  that is capable of being mounted to a flat surface, a tubular structure  34  with first and second open ends  35 A,  35 B, and a flange  36  that is connected to the base plate  32  and used to connect the base plate  32  to the tubular structure  34 . The base plate  32 , tubular structure  34 , and flange  36  each define a portion of a passageway  38  that encloses an electrical conductor, antenna, and/or portion of an antenna. As such, the first rigid portion  26  provides: (a) a mounting surface for attaching the remainder of the first rigid portion  26  to another surface, (b) a structure for engaging the connector  30 , (c) a structure that significantly determines the position of the second rigid portion  28 , and (d) a protective conduit for any conductor, antenna, and/or portion of an antenna located within the passageway  38 . 
     In many applications, the base plate  32 , tubular structure  34 , and flange  36  are made of a dielectric material so as to have little, if any, effect on the operation of the electrically active elements in the antenna system  22 . In one embodiment, the tubular structure  34  is realized using polyvinylchloride (PVC) tubing and acts as a radome, the base plate  32  is made of PVC, and the flange  36  is made of PVC. The use of such plastics allows the base plate  32 , tubular structure  34 , and flange  36  to be joined to one another using any number of technologies known to those skilled in the art. For example, glue and/or melting/welding/soldering technologies can be used to connect the components to one another. The base plate  32 , tubular structure  34 , and flange  36  can each be realized using other materials known to those skilled in the art. If, however, any electrically conductive materials are utilized that will be electrically active when the system  22  is in use, the use of such materials will likely have to be taken into account in the design of the other active antenna elements. Further, other connection methodologies known to those skilled in the art can be employed. For example, the tubular structure  34  and flange  36  can be designed such that a friction or interference fit establishes a suitable connection. Additionally, a first rigid structure is feasible that employs molded or machined parts that reduce or eliminate the need to connect separate parts to one another to form the first rigid portion  26 . For example, the molding of an integrated base plate and first tubular member is feasible and eliminates the need to connect multiple parts to one another to form the first rigid portion. As another example, a structure that is shared by the antenna system  22  and the radio  20  may provide as a suitable first rigid portion. For instance, a chassis or similar structure associated with the radio  20  may, in certain situations, serve as suitable a first rigid structure (i.e., when the radio and antenna are not to be meaningfully separated from one another). 
     While the base plate  32  is shown as having a flat surface that facilitates mounting the first rigid portion  24  to a flat surface, it should be appreciated that a base plate that facilitates mounting the first rigid portion to surfaces having different characteristics (e.g., a curved surface or a “keyed” surface that substantially reduces the possibility of slippage) is feasible. Additionally, the base plate  32  can be fastened to another surface using any appropriate fastening technology (e.g., glue, screw, clamp etc.). The base plate  32  can also be adapted to facilitate a particular fastening technology. For instance, the base plate can be adapted to include one or more slots that retain the straps of one or more hose/pipe clamps that are used to attach a base plate with a curved engagement surface to a tubular member. 
     The first rigid portion  26  also includes one or more electrically active elements  37  that are located in the passageway  38  or a portion of the passageway  38 . For instance, an electrical conductor, antenna, and/or portion of antenna can be located in the passageway  38  or a portion of the passageway  38 . If such an electrically active element is located in the passageway  38  and the element has a flexible nature (e.g., a coaxial cable), the first rigid portion  26  is still considered to be rigid due to the rigid nature of the base plate  32 , the tubular structure  34 , and/or the flange  36 . The electrically active element(s)  37  is/are operatively connected (directly or indirectly) to the electrical conductor  24 . 
     By placing one or more electrically active elements  37  in the passageway  38 , the base plate  32 , tubular structure  34 , and flange  36  surround any such elements and substantially reduce the possibility of any such elements coming into contact with other objects or materials (e.g., water) that could damage the elements. However, in certain applications, the providing of a structure that surrounds any such electrically active elements may not be required. In such instances, the first rigid portion can be realized with a different structure. For instance, if the only electrically active element that is to be associated with the first rigid portion  26  is a coaxial cable that is substantially impervious to substances that are likely to be encountered and any objects that could damage the cable are likely to be situated in a limited angular range, a first rigid portion may include a section of PVC angle iron with the coaxial cable located between the legs of the PVC angle iron and the PVC angle iron oriented so as to protect the cable from objects in the limited angular range. Also, in certain applications, one or more of any electrically active elements may be rigid and robust enough that a surrounding or partially surrounding protective structure is not required to protect any such electrically active elements. 
     The second rigid portion  28  is comprised of a tubular structure  50  with an open end  52  and a closed end  54 . The tubular structure  50  defines a passageway  56  that encloses an electrical conductor, antenna, and/or portion of an antenna. As such, the second rigid portion  28  serves to provide: (a) a structure for engaging the connector  30  and (b) a protective conduit for any conductor, antenna, and/or portion of an antenna located within the tubular structure  50 . In many applications, the tubular structure  50  is made of a dielectric material so as to have little, if any, effect on the operation of the electrically active elements in the antenna system  22 . In one embodiment, the tubular structure  50  is realized using polyvinylchloride (PVC) tubing and acts as a radome. The tubular structure  50  can be realized using other materials known to those skilled in the art. If, however, any electrically conductive material or materials are utilized and such materials will be electrically active during the operation of the system  22 , the use of such materials will likely have to be taken into account in the design of the other active antenna elements. The second rigid portion  28  also includes one or more electrically active elements  55  that are located in the passageway  56 . For instance, an electrical conductor, antenna, and/or portion of antenna can be located in the passageway  56 . If such an electrically active element is located in the passageway  38  and the element has a flexible nature (e.g., a coaxial cable), the second rigid portion  28  is still considered to be rigid due to the rigid nature of the tubular structure  50 . The electrically active element(s)  55  is/are operatively connected (directly or indirectly) to an electrical conductor  57  that is substantially located within the connector  30 . The flexible electrical conductor  57  is also operatively connected (directly or indirectly) to the electrically active element(s)  37  and/or the electrical conductor  24 . 
     By placing one or more electrically active elements  55  in the passageway  56 , the tubular structure  50  surrounds any such elements and substantially reduce the possibility of any such elements coming into contact with other objects or materials (e.g., water) that could damage the elements. However, in certain applications, the providing of a structure that surrounds any such electrically active elements may not be required. In such instances, the first rigid portion can be realized with a different rigid structure, as noted with respect to the first rigid portion. As also noted with respect to the first rigid portion, in certain applications, one or more of any electrically active elements may be rigid and robust enough that a surrounding or partially surrounding protective structure is not required to protect any such electrically active elements. 
     With reference to  FIG. 3 , the connector  30  is comprised of a first ball end link  60 A, a second ball end link  60 B, three intermediate ball-and-socket links  62 A- 62 C, and one intermediate socket-and-socket link  64 . 
     The first ball end link  60 A is adapted to engage the first tubular structure  34  and a socket associated with the intermediate ball-and-socket link  62 A. In this regard and with reference to  FIGS. 4A and 4B , the first ball end link  60 A is comprised of: (a) an open-ended plug  66  with a threaded interior surface and an exterior surface sized to engage and be fixedly attached to the interior surface of the first tubular structure  34  and (b) an open-ended ball structure  68  with a threaded first end  70  for engaging the threaded interior surface of the plug  66 , a ball end  72  for engaging a cooperating socket, and an intermediate portion  74  with a hexagonal exterior surface. The hexagonal exterior surface facilitates the use of a wrench to tighten and pre-load the connection between the threaded exterior surface of the ball structure  68  and the threaded interior surface of the plug  66 . In this regard, the threads are tapered to allow a locking connection between the plug  66  and the ball structure  68  to be achieved. Other structures for connecting the ball structure  68  to the first tubular structure  34  are feasible. For instance, the interior of the first tubular structure  34  could be threaded for engaging the threaded exterior surface of the ball structure  68 . Another possibility is to glue or weld the exterior of the ball structure to the interior of the first tubular structure  34  and thereby avoid the need for threads. With reference to  FIG. 4B , the first ball end link  60 A defines a passageway  76  for accommodating a flexible electrical conductor. 
     The second ball end link  60 B is adapted to engage the second tubular structure  50  and a socket associated with the intermediate socket-and-socket link  64 . The structure of the second ball end link  60 B is substantially identical to that of the first ball end link  60 A. As such, the structure of the second ball end link  60 B is not described further. 
     With reference to  FIGS. 5A and 5B , the intermediate ball-and-socket link  62 A is comprised of a socket structure  80  for engaging a cooperating ball and a ball structure  82  for engaging a cooperating socket. More specifically, the socket structure  80  is adapted to engage the ball structure  72  associated with the first ball end link  60 A and the ball structure  82  is adapted to engage a socket structure associated with the intermediate ball-and-socket link  62 B. The ball structure  82  and socket structure  80  are rigidly connected to one another. Typically, this is achieved by molding, casting or machining so that the link is realized from a single piece of material. Realizing a ball-and-socket link that is rigid can be achieved by other methods, including by the assembly or joining of multiple pieces. With reference to  FIG. 5B , the intermediate ball-and-socket link  62 A defines a passageway  84  for accommodating a flexible electrical conductor. 
     The intermediate ball-and-socket link  62 B is adapted to engage the ball of the intermediate ball-and-socket link  62 A and the socket of the intermediate ball-and-socket link  62 C. Similarly, the intermediate ball-and-socket link  62 C is adapted to engage the ball of the intermediate ball-and-socket link  62 B and a socket of the intermediate socket-and-socket link  64 . The structures of the intermediate ball-and-socket links  62 B and  62 C are substantially identical to that of intermediate ball-and-socket link  62 A. Consequently, the structures of the links  62 B and  62 C are not described further. 
     With reference to  FIGS. 6A and 6B , the intermediate socket-and-socket link  64  is comprised of a first socket  90  for engaging a cooperating ball and a second socket  92  for engaging another cooperating ball. More specifically, the first socket  90  is adapted to engage the ball of the intermediate ball-and-socket link  62 C and the second socket  92  is adapted to engage the ball of the ball end link  60 B. The first socket  90  and the second socket  92  are rigidly connected to one another. Typically, this is achieved by molding, casting or machining so that the link is realized from a single piece of material. Realizing a socket-and-socket link that is rigid can be achieved by other methods, including by the assembly or joining of multiple pieces. With reference to  FIG. 6B , the intermediate socket-and-socket link  64  defines a passageway  94  for accommodating a flexible electrical conductor. 
     Each of the links is used in establishing at least one ball-and-socket joint with an adjacent link. More specifically, the ball end links  60 A,  60 B are each used to establish a single ball-and-socket joint with the immediately adjacent intermediate link. Each of the intermediate ball-and-socket links  62 A and the intermediate socket-and-socket link  64  is used to establish two ball-and-socket joints, one joint with the immediately adjacent link on one side of the intermediate link of interest and the other joint with the immediately adjacent link on the other side of the intermediate link of interest. With reference to  FIG. 7 , the connector  30  has five ball-and-socket joints  100 A- 100 E. 
     With reference to  FIG. 8 , the ball-and-socket joint  100 B established between the intermediate ball-and-socket links  62 A,  62 B is described. The ball-and-socket joint  100 B is comprised of the ball  110  of the intermediate ball-and-socket link  62 A and the socket  112  of the intermediate ball-and-socket link  62 B. To establish the ball-and-socket joint  100 B, the ball  110  is inserted through the opening  114  defined by the edge of the socket  112 . The opening  114  has a smaller diameter than the diameter of the ball  110 . Further, the inner diameter of the socket  112  is slightly less than the diameter of the ball  110 . As such, when the ball  110  is fully inserted into the socket  112 , an interference fit is established between the ball  110  and the socket  112 . The interference fit is designed so that there is sufficient friction between the ball  110  and the socket  112  to maintain the relative positions of the ball  110  and the socket  112  when (a) the maximum torque attributable solely to gravity and within the range of positions that the first and second rigid portions  26 ,  28  are expected to take in a particular application is applied to the joint and (b) a change in the relative positions of the ball and socket is possible. The greatest possible maximum torque is applied to the joint when: (a) the first rigid portion  26 , second rigid portion  28 , and connector  30  are aligned with one another, (b) the first rigid portion  26 , second rigid portion  28 , and connector  30  are oriented so as to be perpendicular to the gravity vector (i.e., positioned to extend horizontally), and (c) the system  22  is only supported by whatever structure the base  32  is attached to. If a particular application precludes or renders unlikely this orientation of the first and second rigid portions  26 ,  28  and the connector  30 , the maximum torque is less. In any event, the interference fit is typically designed so as to maintain the relative positions of the ball  110  and the socket  112  when a force somewhat greater than the maximum torque for a particular application and attributable to gravity is applied to the joint. However, the interference fit is not designed so as to establish so much friction between the ball  110  and the socket  112  that the relative positions of the ball  110  and the socket  112  cannot be altered in appropriate circumstances. To elaborate, the interference fit is designed in the illustrated embodiment so that an individual can apply a force/torque to the joint (i.e., a force/torque that is in greater than the maximum torque for a particular application and resulting solely from the application of gravity) so that the relative positions of the ball  110  and the socket  112  can be altered. The greater force that is needed to alter the relative positions of the ball  110  and the socket  112  can be different depending on the application. It should be appreciated that this criteria is satisfied by each joint in the connector  30 . 
     The establishment of sufficient friction between the ball  110  and the socket  112  to maintain the relative positions when the noted maximum torque is being applied to the system  22  but not so much friction that the relative positions cannot be altered by the application of force/torque to the joint that is sufficiently greater than the relevant maximum force/torque is achieved by using a material or combination of materials for the ball  110  and the socket  112  that have high tensile and compressive strengths and relatively low coefficients of friction. In the illustrated embodiment, one group of materials that meets these requires are ultra-high-molecular-weight-polyethylenes (UHMWPE). Examples of such UHMWPEs are the polyethylenes marketed under the Lennite™ and Nylatron™ marks. In the illustrated embodiment of the connector  30 , each of the intermediate links and at least the open-ended ball structure of each of the ball end links are entirely made from a UHMWPE. The links can be made by casting, molding, or machining UHMWPE to achieve the desired shapes. It should be appreciated that other materials are capable of being used to realize the balls and sockets such that the desired interference fit is obtained. For instance, certain metals and metal alloys can be used to make the balls and sockets. For example, many types of coated metals can be used. The use of a metal or metal alloy to realize the balls and sockets is likely to increase the mass of the system  22  relative to the use of a UHMWPE. Further, the use of combinations of materials or pieces of materials to realize the balls and sockets is feasible. For instance, a metal with the appropriate tensile and compressive strengths but an undesirable coefficient of friction can be coated with a low friction material. 
     With continued reference to  FIG. 8 , due to the interference fit between the ball  110  and the socket  112 , the structure of the socket  113  associated with the link  62 A, and the need for a passageway  116  in the link  62 A to accommodate a flexible electrical conductor, the range of motion of the joint is limited to 22.5°, i.e., the angle between the longitudinal axis  118 A of the link  62 A and the longitudinal axis  118 B of the link  62 B can be no greater than 22.5°. It should be appreciated that if one or more of the factors that are determinative of this range change, the range of motion may be increased or decreased. For instance, if a material can be utilized that allows the desired interference fit to be achieved but allows the wall that defines the portion of the passageway  116  adjacent to the socket  112  to be narrowed, the range of motion can likely be increased. Conversely, if a material is utilized that requires this wall to be made thicker, the range of motion is likely to decrease. 
     With continued reference to  FIG. 8 , the passageway  116  defined by the ball  110  has a frusto-conical portion  120 . The side of the frusto-conical portion  120  is at an angle of 22.5° relative to the longitudinal axis  118 A of the link  62 A. As such, over the relative range of motion of 22.5° provided by the joint  100 B, any electrical conductor that is passing through the passageway  116  of the link  62 A, a passageway  122  of the link  62 B, and an intermediate passageway  124  defined by the ball  110  and the socket  112  will not be subjected to a passageway of decreasing cross-sectional area that could cause the electrical conductor to have a bend with an undesirable bend radius, bind within the connector  30 , be abraded or crimped, or substantially inhibit the joint  100 B from providing the desired range of motion between the ball  110  and the socket  112 . It should be appreciated that a frusto-conical portion could be associated with a passageway associated with a socket of a ball-and-socket joint rather than with the ball of such a joint. However, this is likely to require changes in the structure of the link that would adversely affect the range of motion of the joint. As an alternative to the use of a passageway with a frusto-conical portion, a cylindrical passageway with a larger diameter can be utilized. However, this may also require other changes to the link that would adversely affect the range of motion of the joint and/or compromise the tensile and compressive strength aspects of the portion of the joint through which the larger diameter passageway passes. 
     The other ball-and-socket joints  100 A and  100 C- 100 E are substantially identical to the ball-and-socket joint  100 B. Consequently, these other joints will not be further described. 
     The connector  30  is comprised of six links ( 60 A,  60 B,  62 A- 62 C, and  64 ) from which the five ball-and-socket joints  100 A- 100 E are realized. Each joint provides a range of motion of approximately 22.5°. Cumulatively, the joints  100 A- 100 E provide a range of motion between the first rigid portion  26  and the second rigid portion  28  of approximately 112.5°. It should be appreciated that other combinations of ball end links and intermediate links can be used to produce a connector that provides a different range of motion between the first and second rigid portions. For instance, a connector with two ball end links that are connected to one another by a socket-and-socket link has two ball-and-socket joints. Assuming that each of the joints has a range of motion of 22.5°, the connector provides a range of motion of 45° between the first and second rigid portions. 
     It should be appreciated that the types of link are not limited to ball end links, ball-and-socket links, and socket-and-socket links. With reference to  FIGS. 9A and 9B , a socket end link  130  is also feasible. The socket end link  130  is adapted to engage a tubular structure, such as tubular structure  34  or tubular structure  50 , and a ball associated with a ball end link or with an intermediate link that includes a ball. In this regard, the socket end link  130  is comprised of: (a) an open-ended plug  132  with a threaded interior surface and an exterior surface sized to engage and be fixedly attached to the interior surface of a tubular structure and (b) an open-ended socket structure  134  with a threaded first end  136  for engaging the threaded interior surface of the plug  132 , a socket end  138  for engaging a cooperating ball via an interference fit, and an intermediate portion  140  with a hexagonal exterior surface. The hexagonal exterior surface facilitates the use of a wrench to tighten and pre-load the connection between the threaded exterior surface of the socket structure  134  and the threaded interior surface of the plug  132 . In this regard, the threads are tapered to allow a locking connection between the plug  132  and the socket structure  134  to be achieved. Other structures for connecting the socket structure  134  to a tubular structure, as noted with respect to the ball end link  60 A, are feasible. With reference to  FIG. 9B , the socket end link  130  defines a passageway  142  for accommodating a flexible electrical conductor. 
     With reference to  FIGS. 10A and 10B , an intermediate ball-and-ball link  150  is also feasible. The intermediate ball-and-ball link  150  is comprised of a first ball  152  for engaging a cooperating socket and a second ball  154  for engaging another cooperating socket. More specifically, the first and second balls  152 ,  154  are each adapted to engage, via an interference fit, a socket associated with any end link or intermediate link that has a socket. The first ball  152  and the second  154  are rigidly connected to one another. Typically, this is achieved by molding, casting or machining so that the link is realized from a single piece of material. Realizing a ball-and-ball link that is rigid can be achieved by other methods, including by the assembly or joining of multiple pieces. With reference to  FIG. 10B , the intermediate ball-and-ball link  150  defines a passageway  156  for accommodating a flexible electrical conductor. 
     As should be appreciated, a connector for connecting the first rigid portion  26  and the second rigid portion  28  must include two end links. The two end links can be two ball end links, two socket end links, or a ball end link and socket end link. The connector can also include one or more intermediate links with each link being one of a ball-and-socket link, a ball-and-ball link, or a socket-and-socket link. A connector with only one ball-and-socket joint is realized by connecting a ball end link to a socket end link. A connector with two or more ball joints is established by using two end links and one or more intermediate links. While there is no upper limit on the number of links that can be employed in a connector, it is considered unlikely that a connector that provides a range of motion of greater than 180° will be needed. Further, it should also be appreciated that it is likely to become more difficult to maintain the positions of the first and second rigid portions of the antenna system when the system is being subjected to a force/torque that is solely attributable to gravity or to a somewhat greater force depending upon the application as the number of joints in a connector increases. It should also be appreciated that an antenna system with three or more rigid portions and connectors that each have two or more links and extend between immediately adjacent pairs of the rigid portions is feasible. 
     With reference to  FIGS. 11A-11C , an example of the operation of the antenna system  22  is described. Generally, the antenna system  22  is associated with a foot soldier  170 . In  FIG. 11A , the antenna system  22  is in a state in which the first rigid portion  26 , second rigid portion  28 , and connector  30  are substantially vertically disposed and the foot solder is walking towards an overhead obstacle  172 . In  FIG. 11B , the foot solder  170  is passing under the obstacle and the second rigid portion  28  of the antenna system is engaged by the overhead obstacle  172 . The engagement of the second rigid portion  28  by the overhead obstacle  172  causes a force/torque that is sufficiently greater than the maximum force/torque associated with at least one of the joints of the connector  30 . In response to this greater force/torque, the antenna system  22  allows the relative positions of the first and second rigid portions to be altered such that there is roughly a 90° angle between the first and second rigid portions  26 ,  28 . With reference to  FIG. 11C , after the foot solder  170  has passed under the obstacle  172  and the second rigid portion  28  is no longer being engaged by the obstacle  172  and substantially only gravity is being applied to the system  22 , the system  22  operates so that the roughly 90° angle between the first and second rigid portions  26 ,  28  is maintained. This positional relationship will be maintained until such time as a sufficient force/torque is applied to the second rigid portion  28 . 
     The foregoing description of the invention is intended to explain the best mode known of practicing the invention and to enable others skilled in the art to utilize the invention in various embodiments and with the various modifications required by their particular applications or uses of the invention.