Abstract:
Antennas, integrated driveshaft covers, and methods are disclosed. A particular antenna includes a dielectric layer. The dielectric layer has a first curved surface and a second curved surface opposite the first curved surface. A conductive body has a curved outer surface, where the first curved surface of the dielectric layer is positioned against the curved outer surface. A high frequency (HF) antenna layer is positioned over positioned over the second curved surface of the dielectric layer, where the HF antenna layer is curved to conform to the second curved surface of the dielectric layer. A pair of contacts may be configured to receive an electrical connection for the HF antenna layer. When an HF signal is applied to the pair of contacts, the conductive body interacts with the HF antenna layer to radiate energy.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure is generally related to a high frequency range antenna including or mounted upon a curved conductive body such as a drive shaft cover of a helicopter. 
       BACKGROUND 
       [0002]    Many competing concerns may be considered in designing and outfitting a vehicle such as an aircraft. For example, it is desirable for the aircraft to be durable and to have good aerodynamics while, at the same time, it is desirable for the aircraft to be inexpensive to build and to include a full complement of desired features. 
         [0003]    Providing adequate antennas is one exemplary design issue that can raise such competing concerns. To provide desired bandwidth coverage, an antenna may be subject to particular size and location constraints. At the same time, however, if the antenna protrudes from the aircraft body, the antenna may be exposed to accidental damage from ground personnel or airborne objects, and the antenna may also detract from the aerodynamics of the aircraft. 
         [0004]    In the case of helicopters, finding an available area on the outside of a helicopter body to mount an antenna where the antenna will not interfere with a rotor, a stabilizer, or control surfaces of the helicopter can be difficult. There may be little available area on the helicopter body to mount such an antenna where the antenna can provide coverage in all directions around the helicopter. Mounting a “towel bar” type antenna on a tail boom section of a helicopter makes use of available, largely unused space on the helicopter. However, towel bar type antennas extend outward from the tail boom section and may be subject to damage by personnel servicing the helicopter when the helicopter is not in flight. 
       SUMMARY 
       [0005]    Embodiments disclosed herein include conformal antennas, integrated driveshaft covers for helicopters, and methods for providing a conformal drive shaft cover high frequency (HF) antenna. A curved conductive body may provide a base for a conformal antenna. For example, a driveshaft cover, such as may be found on an upper surface of a helicopter tail boom section, may provide a maintenance access point to enable work to be done on the tail rotor drive shaft and its associated linkages. The driveshaft cover also may provide a curved conductive body for use in a conformal antenna. 
         [0006]    Taking the example of mounting a conformal antenna on a driveshaft cover of a helicopter, the conformal antenna may be mounted on or integrated with the driveshaft cover. In either embodiment, the driveshaft cover and antenna become a unified radiating system. The drive shaft cover, which may be constructed of a conductive material, provides a base for the HF antenna. The HF antenna may include a dielectric layer positioned over substantially all of an outward-facing area of the driveshaft cover. A conductive antenna layer may be positioned over the dielectric layer. The conductive antenna layer, in one embodiment, is a slotted antenna with an interior slot that runs substantially along a length of the driveshaft cover. The conductive antenna layer may be coupled to a radio transceiver by a pair of leads joined to contacts on opposing sides of the interior slot at a mid-point of the length of the interior slot. Size and shape of the antenna layer may be selected to provide effective transmission and reception in HF frequency bands between approximately 1.8 megahertz and 30 megahertz. 
         [0007]    In a particular illustrative embodiment, an antenna includes a dielectric layer that has a first curved surface and a second curved surface opposite the first curved surface. A conductive body has a curved outer surface, where the first curved surface of the dielectric layer is positioned against the curved outer surface. A high frequency (HF) antenna layer is positioned over the second curved surface of the dielectric layer, where the HF antenna layer is curved to conform to the second curved surface of the dielectric layer. A pair of contacts may be configured to receive an electrical connection for the HF antenna layer. When an HF signal is applied to the pair of contacts, the conductive body interacts with the HF antenna layer to radiate energy. 
         [0008]    In another particular illustrative embodiment, an integrated driveshaft cover antenna includes a driveshaft cover including a metal layer. The driveshaft cover is configured to be hingeably secured and electrically coupled to an aircraft tail boom section to cover a driveshaft access opening. A dielectric layer includes a first surface shaped to conform to a curved outer surface of the driveshaft cover and a second surface opposite the first surface. The dielectric layer covers a majority of an area of the curved outer surface of the driveshaft cover. The first surface is secured to the curved outer surface of the driveshaft cover. A slotted patch HF antenna layer is secured to the second surface of the dielectric layer. The slotted patch HF antenna layer has an inner slot. The slotted patch HF antenna layer extends a majority of a length of the dielectric layer. 
         [0009]    In still another particular illustrative embodiment, a method includes providing a dielectric layer having a first face and a second face opposite the first face and having a generally uniform thickness between the first face and the second face. The first face of the dielectric layer is positioned over at least a portion of a curved outer surface of a conductive body. The first face is curved along a first dimension to match a first curvature of the curved outer surface. A curved conductive antenna layer is positioned over the second face of the dielectric layer, where the curved conductive antenna layer is curved along the first dimension to match a second curvature of the second face. The curved conductive layer has opposing antenna faces. The curved antenna layer includes an interior slot between the first antenna face and the second antenna face. The interior slot has a slot length that extends perpendicularly to the first curvature. Transceiver leads are coupled to opposing edges of the interior slot at a midpoint of the slot length. 
         [0010]    The conformal HF antenna or integrated driveshaft cover antenna provides HF coverage in a wide pattern and over a wide frequency range. At the same time, the antenna does not extend outward from the body of the helicopter or other vehicle or structure on which the antenna is mounted. Thus, the antenna is protected from damage. The antenna also does not appreciably affect the aerodynamics of an aircraft or other vehicle on which the antenna is mounted. 
         [0011]    The features, functions, and advantages that have been described can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which are disclosed with reference to the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a side view of an exemplary helicopter equipped with a conformal driveshaft cover high frequency (HF) antenna on an upper surface of a tail boom section; 
           [0013]      FIG. 2  is a top view of the helicopter of  FIG. 1  showing the conformal driveshaft cover HF antenna; 
           [0014]      FIG. 3  is a perspective view of the tail boom section of the helicopter of  FIG. 1  showing an enlarged view of the conformal driveshaft cover HF antenna; 
           [0015]      FIGS. 4 and 5  are side views of the tail boom section of  FIG. 3  showing a hingeably-mounted conformal driveshaft cover HF antenna in closed and open positions, respectively; 
           [0016]      FIGS. 6 and 7  are top views of the tail boom section of  FIGS. 4 and 5  showing the hingeably-mounted conformal driveshaft cover HF antenna in closed and open positions, respectively; 
           [0017]      FIG. 8  is a cross-sectional view of the conformal driveshaft cover HF antenna at a mid-point of the conformal driveshaft cover HF antenna; 
           [0018]      FIG. 9  is a bottom view of an antenna layer of the conformal driveshaft cover HF antenna; 
           [0019]      FIG. 10  is a top view of a tail boom section with a conformal driveshaft cover HF antenna that has a bowtie-shaped internal slot according to a particular embodiment; 
           [0020]      FIG. 11  is a block diagram of an HF transceiver system using an embodiment of the conformal driveshaft cover HF antenna; 
           [0021]      FIG. 12  is a series of perspective diagrams of potential applications of a conformal HF antenna according to particular illustrative embodiments; and 
           [0022]      FIG. 13  is a flow diagram of a particular embodiment of a method of forming a conformal HF antenna. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Particular illustrative embodiments of a conformal driveshaft cover high frequency (HF) antenna make effective use of available aircraft surface space or other surface space while providing a durable, functional HF antenna enabling HF radio communications. For example, by positioning the conformal HF antenna on a driveshaft cover of a helicopter or integrating the conformal HF antenna with the driveshaft cover, an ordinary access panel is replaced with an access panel that functions as part of a radiating HF antenna. The conformal HF antenna may include a dielectric layer and an antenna layer, such as a slotted antenna, that substantially cover the driveshaft cover. The dimensions and configuration of the conformal antenna may enable the aircraft to engage in radio communications in HF frequency bands without the use of a protruding antenna. 
         [0024]    Embodiments of the conformal HF antenna of the present disclosure are not limited to any particular implementation. The present disclosure describes the implementation of a conformal driveshaft cover-based HF antenna mounted on a helicopter as an illustrative example of a conformal antenna that provides desirable radio capabilities, is durable, and makes use of available and potentially underutilized space on a vehicle or other object. The example is provided by way of illustration rather than by limitation; conformal antennas according to the present disclosure may be used on any type of vehicle-based or non-vehicle-based installations. 
         [0025]      FIG. 1  is a side view of an exemplary helicopter  100  equipped with a conformal driveshaft cover high frequency (HF) antenna  110  on an upper surface  120  of a tail boom section  130 . The tail boom section  130  extends from a main fuselage  140  of the helicopter  100 , and includes a tail boom (not shown) that physically supports a tail section  150 . Inside the tail boom section  130 , a driveshaft and associated linkages (not shown in  FIG. 1 ) extend from a main engine (also not shown in  FIG. 1 ) that drives a main rotor  160 . The driveshaft carries power from the main engine to the tail section  150  to drive a tail rotor  170  of the helicopter  100 . 
         [0026]    The conformal driveshaft cover HF antenna  110  is positioned on a driveshaft cover (which in  FIG. 1  is completely covered and thus visually blocked by the conformal driveshaft cover HF antenna  110 ). The driveshaft cover is a doorway in the upper surface  120  of the tail boom section  130  that affords access to the driveshaft system and other components housed in the tail boom section  130 . The driveshaft cover may be long enough to permit access to ends of the driveshaft and wide enough to enable personnel to work with their hands and various tools inside a cavity adjacent the tail boom within the tail boom section  130 . 
         [0027]    In a particular embodiment, the driveshaft cover is hingeably attached to the tail boom section  130 . In this embodiment, the driveshaft cover is more easily replaced or operated upon than fixed portions of the tail boom section  130 . By installing the conformal driveshaft cover HF antenna  110  on the driveshaft cover or integrating the conformal driveshaft cover HF antenna  110  with the driveshaft cover, an existing maintenance access panel may be adapted to serve a useful purpose during flight of the helicopter  100 . 
         [0028]      FIG. 2  is a top view of the helicopter  100  of  FIG. 1  showing the conformal driveshaft cover HF antenna  110 . In a particular embodiment, the conformal driveshaft cover HF antenna  110  has an area that generally covers the driveshaft cover, blocking a view of the driveshaft cover in  FIG. 2 . As shown in  FIG. 2 , the conformal driveshaft cover HF antenna  110  has a length L′  222  that, like the driveshaft cover, extends most of a length L  220  of the tail boom section  130 . 
         [0029]    The conformal driveshaft cover HF antenna  110  may include a dielectric layer  212  positioned over the driveshaft cover. A conductive antenna layer  214  may be positioned over the dielectric layer  214 . In one particular illustrative embodiment, the conductive antenna layer  214  extends approximately the full length L′  222  of the dielectric layer  212 . In a particular embodiment, the conductive antenna layer  214  is not as wide as the dielectric layer  212 . In one particular illustrative embodiment, the conductive antenna layer  214  is a slotted patch antenna. The conductive antenna layer  214  may include an interior opening or slot  216  that has a length L″  226  that extends a majority of the length L′  222  of the dielectric layer  212 . Conductors from a transceiver of the helicopter  100  may be coupled to opposing interior edges of the interior slot  216  at a midpoint of the interior slot  216  to support a desired radiating pattern. 
         [0030]      FIG. 3  is a perspective view of the tail boom section  130  of the helicopter  100  of  FIG. 1 .  FIG. 3  shows an enlarged view of the conformal driveshaft cover HF antenna  110  and a portion of the upper surface  120  of the tail boom section  130 . The conformal driveshaft cover HF antenna  110  has a curvature  310  transverse to the length L  220  of the tail boom section  130 . The curvature  310  may be comparable to that of an ordinary tail boom section driveshaft cover (i.e., a driveshaft cover that does not include an HF antenna). The curvature  310  may provide increased interior space adjacent the tail boom section  130  to accommodate the driveshaft or other internal components (not shown) of the tail boom section  130 . In a particular illustrative embodiment, the dielectric layer  212  and the conductive antenna layer  214  are curved across the conformal driveshaft cover HF antenna  110  transverse to the length L  220  of the tail boom section  130 . The interior slot  216  may be positioned at a mid-point of the curvature  310 . For example, the interior slot  216  may be located at a top of the conformal driveshaft cover HF antenna  110 . 
         [0031]      FIGS. 4 and 5  are side views  400  and  500  of the tail boom section  130  of  FIG. 3  showing a hingeably-mounted conformal driveshaft cover HF antenna  110  in closed and open positions, respectively. The side view  400  of  FIG. 4  shows the dielectric layer  212  extending from the upper surface  120  of the tail boom section  130  toward the interior slot  216  that is positioned at a top of the conformal driveshaft cover HF antenna  110 . 
         [0032]    The side view  500  of  FIG. 5  illustrates the curvature  310  of the conformal driveshaft cover HF antenna  110  in an open position.  FIG. 5  also shows a pair of hinges  510  that hingeably attach the conformal driveshaft cover HF antenna  110  to the tail boom section  130 . In a particular embodiment, the hinges  510  are similar to, interchangeable with, interoperable with, or identical to hinges used to hingeably attach a conventional driveshaft cover to the tail boom section  130  to enable the conventional driveshaft cover to be easily replaced by the conformal driveshaft cover HF antenna  110 . 
         [0033]      FIGS. 6 and 7  are top views  600  and  700  of the tail boom section  130  of  FIGS. 4 and 5  showing the hingeably-mounted conformal driveshaft cover HF antenna  110  in closed and open positions, respectively. As shown in the closed view  600  of  FIG. 6 , when the conformal driveshaft cover HF antenna  110  is in the closed position, the conformal driveshaft cover HF antenna  110  may be secured to the tail boom section  130  by one or more latches  610 . The latch  610  may be a pawl latch, a buckle, or any other suitable type of mechanical latch to hold the conformal driveshaft cover HF antenna  110  in a closed position when desired. In a particular embodiment, the latch  610  is similar to, interchangeable with, or the same as one or more latches used to secure a conventional driveshaft cover in a closed position to enable the conventional driveshaft cover to be easily replaced by the conformal driveshaft cover HF antenna  110 . 
         [0034]    The top view  700  of  FIG. 7  shows the conformal driveshaft cover antenna  110  in the open position.  FIG. 7  shows the latch  610  in an open position. When the latch  610  is in the open position, the conformal driveshaft cover HF antenna  110  may be raised on the hinges  510  to permit access to an underside  720  of the conformal driveshaft cover HF antenna  110  as well as to an interior  730  of the tail boom section  130 . In a particular illustrative embodiment, the underside  720  of the conformal driveshaft cover HF antenna  110  is a bottom layer of the conformal driveshaft cover HF antenna  110 . In a particular embodiment, the underside  720  of the conformal driveshaft cover HF antenna  110  is a conductive panel, comprised of metal or another material, made of the same material as a remainder of the tail boom section  130 . In this embodiment, the conductive panel may be electrically and mechanically secured to the tail boom section  130  by the hinges  510 , the latch  610 , one or more other connectors, or any combination thereof. The conductive layer may provide a radiating base for other layers  212  and  214  of the conformal driveshaft cover HF antenna  110 . For example, the conductive layer may interact with the HF antenna layer to radiate the energy. 
         [0035]    As also shown in  FIG. 7 , the underside  720  of the conformal driveshaft cover HF antenna  110  may include an access opening  740  to enable electrical connections to be made to the antenna layer  214  (not shown in  FIG. 7 ) by conductors (also not shown in  FIG. 7 ) extending through portions of the conformal driveshaft cover HF antenna  110 . In a particular embodiment, the electrical connections to the antenna layer  214  are made at opposing sides at a mid-point of the interior slot  216 . Thus, the access opening  740  may be positioned generally at a mid-point of the conformal driveshaft cover HF antenna  110  to lie beneath the mid-point of the interior slot  216  (not shown in  FIG. 7 ). However, in other configurations, the electrical connections to the antenna layer may be made at other locations of the antenna layer  214 . Additionally, in other configurations, the electrical connections may be made using wire or other conductors that extend between the dielectric layer  212  of the conformal driveshaft cover HF antenna  110  and the driveshaft cover. 
         [0036]      FIG. 8  is a cross-sectional view  800  of the conformal driveshaft cover HF antenna  110 . The cross-sectional view  800  is taken approximately at a mid-point along a length of the conformal driveshaft cover HF antenna  110 . The cross-sectional view  800  illustrates electrical connections to the conformal driveshaft cover HF antenna  110 . For example, the cross-sectional view  800  shows a first face  814  of the dielectric layer  212  positioned over a curved outer surface  818  of a conductive body or conductive layer  810 . The conductive body or conductive layer  810  provides a conductive and structurally-supportive base for the conformal driveshaft cover HF antenna  110 . The first face  814  of the dielectric layer is curved in a first dimension perpendicular to the thickness T  812  to correspond with a first curvature  817  of the outer surface  818  of the conductive body or conductive layer  810 . 
         [0037]    According to a particular embodiment, the dielectric layer  212  may be a thermoplastic foam, such as a thermoplastic syntactic, foam, or a polymer foam with a generally uniform thickness T  812  of approximately one half to two inches to desirably insulate the antenna layer  214  from the conductive body or conductive layer  810  to support desired transmission capabilities of the HF antenna  110 . 
         [0038]    The antenna layer  214  is positioned over a second face  816  of the dielectric layer  212 . The antenna layer  214  has a first antenna face  821  and an opposing second antenna face  823 . The first antenna face  821  has a curvature in the first dimension that matches a second curvature  819  of the second face  816  of the dielectric layer  812 . The interior slot  216  extends between the first antenna face  821  and the second antenna face  823 . The interior slot  216  along a slot length that is perpendicular to the first curvature  817  of the outer surface of the conductive body and the second curvature  819  of the second face  816  of the dielectric layer  212 . 
         [0039]    A protective layer  820  may cover the antenna layer  214 , the dielectric layer  212 , or both. According to a particular illustrative embodiment, to prevent interference with operation of the conformal driveshaft cover HF antenna  110 , the protective outer layer  820  includes a low dielectric loss quartz fiber composite material. ASTROQUARTZ™ is one example of a suitable low dielectric loss material that may provide adequate protection for the conformal driveshaft cover HF antenna  110 . In addition, the conformal driveshaft cover HF antenna  110  may include a lightning strike appliqué  825  covering exposed outer surfaces of the slotted patch HF antenna, the dielectric layer, and the driveshaft cover. The lightning strike appliqué  825  may include a an expanded mesh, a nonconductive substrate supporting a plurality of patches of conductive material, or any other form of appliqué configured to disperse electrical charges. The lightning strike appliqué  825  should be of a type that will not interfere or only minimally interfere with HF radio signals. The lightning strike appliqué  825  protects the conformal driveshaft cover HF antenna  110  from damage caused by lightning strikes by dispersing the electric charge throughout the lightning strike appliqué  825  or over the surface of the lightning strike appliqué  825 . The lightning strike appliqué  825  may also protect other parts of the helicopter by dispersing the electrical charge presented by a lightning strike before that charge is conducted to the other parts of the helicopter. Note that thicknesses of the protective layer  820  and the lightning strike appliqué  825  may be exaggerated for visual clarity in  FIG. 8  from actual thicknesses of the protective layer  820  and the lightning strike appliqué  825  that may be deployed on the conformal driveshaft cover HF antenna  110 . 
         [0040]    In a particular illustrative embodiment, the antenna layer  214  is electrically connected to a transceiver (not shown in  FIG. 8 ) at connections  830  on opposing sides of the interior slot  216  by a pair of conductors  840 . In a particular illustrative embodiment, the connections  830  are at a midpoint of the slot length of the interior slot  216 , as shown in the midpoint cross-section of  FIG. 8 . The conductors  840  may pass through a microstrip balun  860  or a similar current balancing structure, to a high power connector  850  that is coupled to the transceiver. The high power connector  850  may be adapted to be coupled to one or more conductors (not shown in  FIG. 8 ) that extend beneath or through the dielectric layer  212  along the length of the conformal driveshaft cover RE antenna  110  to the transceiver. 
         [0041]      FIG. 9  is a bottom view  900  of an antenna layer  214  of the conformal driveshaft cover HF antenna  110  showing the pair of conductors  840  extending from the connections  830  approximately at a midpoint  910  of the length L″  226  of the interior slot  216  of the conformal driveshaft cover HF antenna  110 . The shape and size of the antenna layer  214  (including the shape and size of the interior slot  216 ), the dielectric layer  212 , and the conductive layer  810 , and the manner in which the antenna layer  214  is electrically connected to a transceiver, may enable the conformal driveshaft cover HF antenna  110  to radiate vertically polarized HF signals (illustrated in  FIG. 8  as signals  890 ) and horizontally polarized HF signals  990 , or both. The HF signals may be radiated in a bandwidth between approximately 1.8 megahertz and 30 megahertz. In a particular embodiment, the shape and size of the antenna layer  214  may be configured to radiate vertically polarized signals at one or more frequencies and to radiate horizontally polarized signals at one or more different frequencies. For example, the vertically polarized HF signals  890  may be radiated in a bandwidth between approximately 3 megahertz and 30 megahertz and the horizontally polarized HF signals  990  may be radiated in a bandwidth between approximately 1.8 megahertz and 15 megahertz. 
         [0042]      FIG. 10  is a top view  1000  of the tail boom section  130  including another embodiment of a conformal driveshaft cover HF antenna  1010 . The conformal driveshaft cover HF antenna  1010  may include a dielectric layer  1212  and an antenna layer  1014 . In a particular embodiment, the antenna layer  1014  includes a bowtie-shaped internal slot  1016 . Other aspects of the conformal driveshaft cover HF antenna  1010  may be similar to attributes of the conformal driveshaft cover HF antenna  110  of  FIGS. 1-9 . For example, the dielectric layer  1212  may be similar to the dielectric layer  212  described with reference to  FIGS. 1-9 . Additionally, the conformal driveshaft cover HF antenna  1010  may be coupled by hinges, latches, or both to the tail boom section  130  on the upper surface  120  of the tail boom section  130 . The bowtie-shaped internal slot  1016  may enhance the radiating patterns of the conformal driveshaft cover HF antenna  1010 . 
         [0043]      FIG. 11  is a block diagram of an HF transceiver system  1100  using an embodiment of a conformal driveshaft cover HF antenna  1110 . The HF transceiver system  1100  includes an HF transceiver  1120  that includes a first contact  1122  and a second contact  1124  to electrically connect to the conformal driveshaft cover HF antenna  1110 . High power connectors  1150  may be used to couple conductors  1140 , via a balun or other current balancing device  1160 , to the conformal driveshaft cover HF antenna  1110 . The HF transceiver system  1100  also includes a pair of antenna leads  1170 . A first end of each of the antenna leads  1170  may be received at an opposing inner edge of an inner slot of an antenna layer of the conformal driveshaft cover HF antenna  1110 . A second end of each of the antenna leads  1170  may be configured to be coupled to the HF transceiver  1120  (e.g., via the current balancing device  1160 ). 
         [0044]      FIG. 12  is a series of perspective diagrams of potential applications  1210 - 1260  of a conformal HF antenna according to particular illustrative embodiments of the present disclosure. Embodiments of the conformal HF antenna may be suitable and beneficial for a number of implementations where horizontally-polarized and vertically-polarized HF communications may be desirable. 
         [0045]    Fixed wing aircraft, such as the aircraft  1210 , may employ a conformal HF antenna. A conformal HF antenna  1212  may be placed on a rear fuselage  1214  of the aircraft or another section of the aircraft fuselage. Alternatively, a conformal HF antenna  1216  may be mounted on a leading edge  1218  of an aircraft wing. In both cases, a curved portion of the body or wing of the aircraft  1210  provides a suitably conductive layer on which to mount a conformal HF antenna as previously described. An unmanned aerial vehicle (UAV)  1220  may employ a conformal HF antenna  1222  mounted on an engine nacelle  1224  or other surface of the UAV  1120 . 
         [0046]    A submarine  1230  may employ a conformal HF antenna  1232  on an upper surface  1234  that extends above the water when the submarine  1230  surfaces. Although HF communications are attenuated underwater, having the conformal HF antenna  1232  mounted on the upper surface  1234  of the submarine  1230  will enable HF communications when the submarine  1230  surfaces. The conformal HF antenna  1232  thus may replace another mast-mounted antenna that may create drag on the submarine  1230  or be prone to damage. A surface boat  1240  also may employ a conformal HF antenna  1242  mounted on a housing  1244  or other surface of the boat  1240 . 
         [0047]    A land-based vehicle, such as a truck  1250  may employ a conformal HF antenna  1252 . In the case of an emergency vehicle, such as the truck  1250  of  FIG. 12 , the conformal HF antenna  1252  may be mounted atop a light bar  1254  or other underutilized structure on the body of the truck  1250 . 
         [0048]    A fixed structure, such as the building  1260 , also may employ a conformal HF antenna  1262 . The building  1260 , which in the example of  FIG. 12  is a Quonset hut, has a curved roof  1264  that provides a suitable conductive body or conductive layer to support the conformal HF antenna  1262 . However, any structure may be configured to use a conformal HF antenna by using another conductive body or conductive layer found on the structure or by providing a conductive body or conductive layer for the purpose of providing a base for the conformal HF antenna. 
         [0049]      FIG. 13  is a flow diagram of one particular illustrative embodiment of a method  1200  of forming a conformal HF antenna. A layer of a dielectric layer having a first face and a second face opposite the first face and having a generally uniform thickness between the first face and the second face is provided, at  1302 . The first face is positioned over at least a portion of a curved outer surface of a conductive body, at  1304 . The first face is curved along a first dimension to match a first curvature of the curved outer surface. A curved conductive antenna layer is positioned over the second face, at  1306 . The curved conductive antenna layer has a first antenna face and a second antenna face that are curved along the first dimension such that the first antenna face matches a second curvature of the second face of the dielectric layer. The curved antenna layer includes an interior slot between the opposing antenna faces. The interior slot has a slot length that extends perpendicularly to the first curvature. Transceiver leads are coupled to opposing edges of the interior slot at a midpoint of the slot length, at  1308 . For example, the method  1300  of  FIG. 13  may be used to form a conformal HF antenna on a driveshaft cover of a helicopter to create a conformal driveshaft cover HF antenna such as described with reference to  FIGS. 1-11 . 
         [0050]    The illustrations of the embodiments described herein are intended to provide a general understanding of the structure of the various embodiments. The illustrations are not intended to serve as a complete description of all of the elements and features of apparatus and systems that utilize the structures or methods described herein. Many other embodiments may be apparent to those of skill in the art upon reviewing the disclosure. Other embodiments may be utilized and derived from the disclosure, such that structural and logical substitutions and changes may be made without departing from the scope of the disclosure. For example, method steps may be performed in a different order than is shown in the figures or one or more method steps may be omitted. Accordingly, the disclosure and the figures are to be regarded as illustrative rather than restrictive. 
         [0051]    Moreover, although specific embodiments have been illustrated and described herein, it should be appreciated that any subsequent arrangement designed to achieve the same or similar results may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the description. 
         [0052]    The Abstract of the Disclosure is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together or described in a single embodiment for the purpose of streamlining the disclosure. This disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, the claimed subject matter may be directed to less than all of the features of any of the disclosed embodiments.