Patent Publication Number: US-2023135141-A1

Title: Antenna heater and methods for preventing ice formation on electromagnetic wave antennas

Description:
FIELD 
     This disclosure relates generally to electromagnetic wave antennas, and more particularly to preventing ice formation on such antennas. 
     BACKGROUND 
     Antennas may be used to transmit data to or receive data from other transmission devices via electromagnetic waves. Often times, an antenna requires a fairly unobstructed path between the antenna and the data transmission devices for the most efficient transmission of data. Accordingly, antennas are often located in geographic locations where relatively long-range unobstructed paths are more prevalent, such as high altitude, remote, and/or low-temperature or freezing locations. 
     Although positioning an antenna at a high altitude, remote, and/or low-temperature or freezing locations can promote data transmission over long ranges, these locations often experience harsh environmental conditions that can disrupt the ability of the antenna to effectively transmit data. For example, in cold weather environments, ice may form on the antennas, which can attenuate the electromagnetic waves transmitted from or received by the antenna. 
     Conventional approaches for reducing the formation of ice on an electromagnetic wave antenna have various shortcomings. According to one approach, a large mechanical shield or overhang is positioned above the antenna to redirect or catch snow and ice to prevent the snow or ice from falling onto the antenna. However, these mechanical shields may fail to prevent snow or ice from contacting the antenna from the side (e.g., in high-wind situations in which the snow or other precipitations contacts the antenna despite the mechanical shield) and may fail to effectively prevent the accretion of ice on the antennas. Another approach includes wrapping an antenna in a large bag made of a low-friction material, which is intended to prevent ice accretion on the bag and thus on the antenna. 
     These passive approaches are not efficient or reliable at preventing the accumulation of snow or formation of ice on an antenna. Moreover, installing large mechanical shields and bags on an antenna in the field is a difficult task that often requires at least two technicians. Additionally, large mechanical shields and bags on an antenna add significant weight and wind resistance to structures supporting the antenna. 
     SUMMARY 
     The subject matter of the present application has been developed in response to the present state of the art, and, in particular, in response to the problems and needs of conventional devices and methods of addressing the accumulation of snow, the formation of ice, or both on an antenna or multiple antennas. The subject matter of the present application may reduce or prevent the accumulation of snow and/or the formation of ice on an electromagnetic wave antenna in an efficient and reliable manner, and may also be easy to install such that, in some cases, it may be installed by a single technician In view of the foregoing, the subject matter of the present application has been developed to provide an antenna heater and corresponding methods, that overcome at least some of the shortcomings of the prior art. 
     Disclosed herein is an antenna heater for heating an antenna comprising heating panel, configured for attachment to the antenna and comprising heating tracks. The heating tracks are spaced apart from each other and each comprises an electrically-conductive trace and positive temperature coefficient (PTC) elements. The PTC elements are electrically connected to the electrically-conductive trace, spaced apart along the electrically-conductive trace, and made of a PTC material having an equilibrium temperature greater than 0° C. The preceding subject matter of this paragraph characterizes example 1 of the present disclosure. 
     The heating panel further comprises an outer cover and an inner cover that is spaced apart from the outer cover such that a gap is defined between the outer cover and the inner cover. The heating tracks are fixed to one of the outer cover or the inner cover, and are located within the gap. The preceding subject matter of this paragraph characterizes example 2 of the present disclosure, wherein example 2 also includes the subject matter according to example 1, above. 
     The antenna heater further comprises a gasket between the outer cover and the inner cover. The gasket seals the gap and defines the outer periphery of the heating panel. The preceding subject matter of this paragraph characterizes example 3 of the present disclosure, wherein example 3 also includes the subject matter according to example 2, above. 
     The outer cover and the inner cover are disk-shaped. A shape of the outer periphery of the heating panel is circular. A shape of the first clamp arm is a semi-circle. A shape of the second clamp arm is a semi-circle. The preceding subject matter of this paragraph characterizes example 4 of the present disclosure, wherein example 4 also includes the subject matter according to any one of examples 2-3, above. 
     The electrically-conductive traces of the heating tracks are uniformly spaced apart from each other. The PTC elements are sized such that the PTC elements underlay between 1% and 3% of the outer cover. The preceding subject matter of this paragraph characterizes example 5 of the present disclosure, wherein example 5 also includes the subject matter according to any one of examples 2-4, above. 
     The antenna heater further comprises a first clamp arm and a second clamp arm, coupleable to the first clamp arm such that, when coupled, the first clamp arm and the second clamp arm surround a majority of an outer periphery of the heating panel. The preceding subject matter of this paragraph characterizes example 6 of the present disclosure, wherein example 6 also includes the subject matter according to any one of examples 2-5, above. 
     The heating panel is fixed to the first clamp arm such that the heating panel and the first clamp arm do not move relative to each other. The preceding subject matter of this paragraph characterizes example 7 of the present disclosure, wherein example 7 also includes the subject matter according to example 6, above. 
     First end portions of the first clamp arm and the second clamp arm are pivotally coupled to each other such that the second clamp arm is pivotable relative to the first clamp arm at the first end portions of the first clamp arm and the second clamp arm. The first clamp arm comprises a first-clamp-arm lock portion at a second end portion of the first clamp arm. The second clamp arm comprises a second-clamp-arm lock portion at a second end portion of the second clamp arm. The first-clamp-arm lock portion and the second-clamp-arm lock portion are engageable to selectively lock together the second end portions of the first clamp arm and the second clamp arm. The preceding subject matter of this paragraph characterizes example 8 of the present disclosure, wherein example 8 also includes the subject matter according to example 7, above. 
     Each one of the first clamp arm and the second clamp arm defines a U-shaped channel that has a width at least twice a thickness of the heating panel. The preceding subject matter of this paragraph characterizes example 9 of the present disclosure, wherein example 9 also includes the subject matter according to any one of examples 6-8 above. 
     The PTC elements of each one of the heating tracks are mounted directly to the electrically-conductive trace of the heating track. The preceding subject matter of this paragraph characterizes example 10 of the present disclosure, wherein example 10 also includes the subject matter according to any one of examples 1-9 above. 
     The electrically-conductive traces of the heating tracks are electrically connected together in parallel. The preceding subject matter of this paragraph characterizes example 11 of the present disclosure, wherein example 11 also includes the subject matter according to any one of examples 1-10 above. 
     A distance between adjacent ones of the PTC elements  130  is such that signal attenuation, caused by the antenna heater is between 0 dB and 2 dB when the antenna is operated without foreign material on the antenna. The preceding subject matter of this paragraph characterizes example 12 of the present disclosure, wherein example 12 also includes the subject matter according to any one of examples 1-11 above. 
     Further disclosed herein is an antenna heater system. The antenna heater system comprises an antenna heater, comprising a heating panel, configured for attachment to an antenna and comprising heating tracks, wherein the heating tracks are spaced apart from each other and each comprises an electrically-conductive trace and positive temperature coefficient (PTC) elements. The PTC elements are electrically connected to the electrically-conductive trace, spaced apart along the electrically-conductive trace, and made of a PTC material having an equilibrium temperature greater than 0° C. The antenna heater system also comprises a temperature sensor, configured to detect temperature of air external to the antenna heater. The antenna heater system further comprises a humidity sensor, configured to detect relative humidity of air external to the antenna heater. The antenna heater system additionally comprises a control module, configured to supply electrical power to the electrically-conductive traces of the heating tracks, such that the PTC elements of the heating tracks generate heat, only when the temperature of the air detected by the temperature sensor is below a temperature threshold and the relative humidity of the air detected by the humidity sensor is above a humidity threshold. The preceding subject matter of this paragraph characterizes example 13 of the present disclosure. 
     The temperature threshold is between 1° C. and 10° C., inclusive, and the humidity threshold is between 50% and 100%, inclusive. The preceding subject matter of this paragraph characterizes example 14 of the present disclosure, wherein example 14 also includes the subject matter according to example 13, above. 
     The equilibrium temperature of the PTC material of each one of the PTC elements is greater than 10° C. and less than 35° C. The preceding subject matter of this paragraph characterizes example 15 of the present disclosure, wherein example 15 also includes the subject matter according to example 14, above. 
     The control module is further configured to continuously increase a current of the electrical power from zero to a maximum current over a predetermined time interval in response to the temperature of the air detected by the temperature sensor being below the temperature threshold and the relative humidity of the air detected by the humidity sensor being above the humidity threshold. The preceding subject matter of this paragraph characterizes example 16 of the present disclosure, wherein example 16 also includes the subject matter according to any one of examples 13-15, above. 
     Additionally disclosed herein is a method of preventing ice formation on an antenna. The method comprising a step of activating an antenna heater, mounted to the antenna, to supply heat to the antenna only when air, around the antenna, has a temperature below a temperature threshold and has a relative humidity above a humidity threshold. Activating the antenna heater comprises heating positive temperature coefficient (PTC) elements of the antenna heater up to an equilibrium temperature of PTC material of the PTC elements. The preceding subject matter of this paragraph characterizes example 17 of the present disclosure. 
     The antenna is a drum antenna comprising a hollow base, defining a signal transmission opening through which electromagnetic waves are transmitted from the drum antenna and received by the drum antenna, and an external cover that covers the signal transmission opening and encloses the hollow base. The method further comprises a step of mounting a heating panel of the antenna heater onto the hollow base such that the heating panel covers the external cover. The preceding subject matter of this paragraph characterizes example 18 of the present disclosure, wherein example 18 also includes the subject matter according to example 17, above. 
     The step of mounting the heating panel of the antenna heater onto the hollow base comprises receiving a first portion of an outer ledge of the antenna into a first-clamp-arm channel of a first clamp arm of the antenna heater, receiving a second portion of the outer ledge of the hollow base into a second-clamp-arm channel of a second clamp arm of the antenna heater, and when the first portion of the outer ledge is received into the first-clamp-arm channel and the second portion of the outer ledge is received into the second-clamp-arm channel, locking together the first clamp arm and the second clamp arm. The preceding subject matter of this paragraph characterizes example 19 of the present disclosure, wherein example 19 also includes the subject matter according to example 18, above. 
     The heating panel is fixed to the first clamp arm, such that the heating panel does not move relative to the first clamp arm and such that the heating panel is moved into position over the external cover of the antenna as the first portion of the outer ledge is received into the first-clamp-arm channel. The preceding subject matter of this paragraph characterizes example 20 of the present disclosure, wherein example 20 also includes the subject matter according to example 19, above. 
     The described features, structures, advantages, and/or characteristics of the subject matter of the present disclosure may be combined in any suitable manner in one or more examples and/or implementations. In the following description, numerous specific details are provided to impart a thorough understanding of examples of the subject matter of the present disclosure. One skilled in the relevant art will recognize that the subject matter of the present disclosure may be practiced without one or more of the specific features, details, components, materials, and/or methods of a particular example or implementation. In other instances, additional features and advantages may be recognized in certain examples and/or implementations that may not be present in all examples or implementations. Further, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the subject matter of the present disclosure. The features and advantages of the subject matter of the present disclosure will become more fully apparent from the following description and appended numbered paragraphs, or may be learned by the practice of the subject matter as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be rendered by reference to specific examples that are illustrated in the appended drawings. Understanding that these drawings, which are not necessarily drawn to scale, depict only certain examples of the subject matter and are not therefore to be considered to be limiting of its scope, the subject matter will be described and explained with additional specificity and detail through the use of the drawings, in which: 
         FIG.  1    is a perspective, schematic view of an antenna tower having multiple antennas, according to one or more examples of the present disclosure; 
         FIG.  2    is a perspective, schematic view of an antenna, according to one or more examples of the present disclosure; 
         FIG.  3    is a perspective, schematic view of an antenna assembly, according to one or more examples of the present disclosure; 
         FIG.  4    is a perspective, schematic view of an antenna assembly, according to one or more examples of the present disclosure; 
         FIG.  5    is a perspective, sectional, schematic view of the antenna assembly of  FIG.  4   , taken along line  5 - 5  of  FIG.  4   , according to one or more examples of the present disclosure; 
         FIG.  6    is a perspective, sectional, schematic view of a portion of an antenna assembly, according to one or more examples of the present disclosure; 
         FIG.  7    is a perspective, partially sectioned, schematic view of an antenna heater, according to one or more examples of the present disclosure; 
         FIG.  8    is a plan, schematic view of a cover and heating tracks of an antenna heater, according to one or more examples of the present disclosure; 
         FIG.  9    is a perspective, schematic view of a cover and heating tracks of an antenna heater, according to one or more examples of the present disclosure; 
         FIG.  10    is a perspective, schematic view of an antenna heater being installed onto an antenna, according to one or more examples of the present disclosure; 
         FIG.  11    is a perspective, schematic view of the antenna heater of  FIG.  10    partially installed on the antenna, according to one or more examples of the present disclosure; 
         FIG.  12    is a perspective, schematic view of the antenna heater of  FIG.  10    fully installed on the antenna, according to one or more examples of the present disclosure; 
         FIG.  13    is a block diagram of an antenna system, according to one or more examples of the present disclosure; 
         FIG.  14    is a schematic flow chart of a method of preventing ice formation on an antenna, according to one or more examples of the present disclosure; and 
         FIGS.  15 A- 15 C  are graphs illustrating current-voltage, resistance-temperature, and power-voltage characteristics, respectively, for a positive temperature coefficient (PTC) material, according to one or more examples of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference throughout this specification to “one example,” “an example,” or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the present disclosure. Appearances of the phrases “in one example,” “in an example,” and similar language throughout this specification may, but do not necessarily, all refer to the same example. Similarly, the use of the term “implementation” means an implementation having a particular feature, structure, or characteristic described in connection with one or more examples of the present disclosure, however, absent an express correlation to indicate otherwise, an implementation may be associated with one or more examples. 
     The subject matter of the present disclosure includes examples of an antenna system and corresponding antenna heater that actively and intelligently prevents the accumulation of snow, the formation of ice, or both on an antenna of the antenna system in a safe, efficient, and environmentally sensitive manner. In certain examples, the antenna heater utilizes positive temperature coefficient (PTC) materials that self-regulate the heat generated by the antenna heater without the need for complex control systems, which promotes reliability, longevity, and a reduction in operational and servicing costs. According to some examples, the antenna heater enables safe and easy retrofitting of an antenna in the field by a single service engineer with zero or minimal changes to the existing software or hardware of the antenna. Additionally, the antenna heater may have a limited and/or negligible effect, if any, on the attenuation of signals transmitted from or received by the antenna to which the antenna heater is coupled. 
       FIG.  1    illustrates an example of an antenna tower  101 . The antenna tower  101  has multiple antennas  102 . The antennas  102  of  FIG.  1    are depicted as drum antennas, but could be other types of antennas known in the art. Generally, as shown in  FIG.  2   , according to one example, the antenna  102 , as used in the illustrative examples disclosed herein, is a drum antenna that includes a hollow base  114  and an external cover  116  fixed to the hollow base  114 . Although the description herein makes reference to a drum antenna, the description can be applied to other types of antennas, such as antennas with different shapes or different structures. For example, in addition to a circular-shaped drum antenna, the description can be applied to drum antenna having non-circular outer peripheral shapes, such as rectangular or square. Additionally, although the external cover  116  of the drum antenna shown in the illustrated examples is flat or planar, in some examples, the description can be applied to an external cover of a drum antenna or other type of antenna that has a non-planar or contoured external cover. 
     In the example of  FIG.  2   , the hollow base  114  is cone or dome shaped and converges in a directly away from the external cover  116 . However, in other examples, such as some of the antennas  102  shown in  FIG.  1   , the hollow base  114  is cylindrical shaped. The hollow base  114  includes a signal transmission opening  115  through which electromagnetic waves (e.g., signals) are transmitted from the antenna  102  and received by the antenna  102  (see, e.g.,  FIGS.  5  and  6   ). Although not shown, the antenna  102  includes a signal transmitter, a signal receiver, or a signal transceiver. The signal transmitter generates and transmits electromagnetic waves, which enables the antenna  102  to operate as a data uplink. The signal receiver receives electromagnetic waves generated by other transmitters (e.g., other antenna), which enables the antenna  102  to operate as a data downlink. The signal transceiver generates and receives electromagnetic waves, which enables the antenna  102  to operate as both a data uplink and data downlink. Power for transmitting and/or receiving electromagnetic waves is provided by a power supply  104 . 
     The external cover  116  overlays the signal transmission opening  115  and encloses the hollow base  114 . An interior cavity  132  of the antenna  102  is thus defined between the hollow base  114  and the external cover  116 . The external cover  116  helps prevent debris from entering the interior cavity  132  and disrupting signal transmission and/or signal reception, such as by attenuating signals sent or received by the antenna  102 . In some examples, such as shown, the external cover  116  is flat. Moreover, the external cover  116  has an outer peripheral shape that corresponds with (e.g., matches) that of the hollow base  114 . For example, the external cover  116  can be disk shaped and have an outer peripheral shape that is circular. The external cover  116  is made of a material that provides sufficient protection from debris, while having limited effects, if any, on the attenuation of the electromagnetic waves passing through the external cover  116 . In some examples, the external cover  116  is made of a hardened plastic material, such as a fiber-reinforced polymer (e.g., fiberglass). 
     Referring to  FIGS.  5  and  6   , in some examples, the antenna  102  further comprises a backing layer  117  that is coupled to and supports the external cover  116 . The backing layer  117  promotes rigidity of the external cover  116 . Additionally, in certain examples, the backing layer  117  is made of a thermally insulating material, such as a hardened foam, that helps insulate the interior cavity  132  from harsh environmental conditions. The external cover  116  can be affixed to the backing layer  117 , such as via an adhesive or with fasteners. 
     Generally, the external cover  116  is coupled to the hollow base  114  by a ring  161  that extends circumferentially about the hollow base  114  and the external cover  116  to effectively clamp the external cover  116  to the hollow base  114 . The ring  161  has a generally L-shaped cross-section and defines, along with an outer flange  119  or shelf of the hollow base  114 , an outer ledge  118  of the antenna  102  (see, e.g.,  FIGS.  2  and  6   ). Because the ring  161  and outer flange of the hollow base  114  is circular, in some examples, the outer ledge  118  also is circular. In some examples, as best shown in  FIG.  6   , the ring  161  attaches, such as via fasteners, to the outer flange of the hollow base  114 , which defines the signal transmission opening  115 . When attached to the hollow base  114 , a top flange  129  of the ring  161  overlays a peripheral portion of the external cover  116  to retain the external cover  116  (and, e.g., the backing layer  117 ) against the hollow base  114  (see, e.g.,  FIG.  6   ). 
     As previously presented, in some harsh environmental conditions, such as those with colder temperatures, the antenna  102  is prone to the accumulation of snow, formation of ice, or both, on the external cover  116 . The accumulation of snow, the formation of ice, or both on the external cover  116  can cause a dramatic increase in the attenuation of signals transmitted from or received by the antenna  102 . Referring to  FIG.  3   , and according to some examples, the subject matter of the present disclosure includes an antenna heater  110  that is coupled to the antenna  102  and is operable to produce heat that reduces or prevents the accumulation of snow, the formation of ice, or both, on the external cover  116  and on the antenna heater  110 . In this manner, signal attenuation, due to the formation of ice on the external cover  116 , can be reduced or prevented. 
     As shown in  FIG.  4   , the antenna heater  110  includes a heating panel  124  and a clamp assembly  120 . As will be explained in more detail, the clamp assembly  120  mounts the heating panel  124  to the antenna  102  to form an antenna assembly  131 , which includes the antenna  102  and the antenna heater  110 . The heating panel  124  of the antenna heater  110  includes an outer cover  126  that is exposed to the environment. In some examples, the outer cover  126  is flat or planar, and is parallel with the external cover  116  of the antenna  102 . The heating panel  124  also includes an inner cover  134  that is spaced apart from the outer cover  126  such that a gap  136  is defined between the outer cover  126  and the inner cover  134  (see, e.g.,  FIG.  5   ). The inner cover  134  can also be flat or planar, and parallel with the outer cover  126 , such that the heating panel  124  has a multi-layer sandwich configuration. The outer cover  126  and the inner cover  134  can be made of a strong and durable material. Moreover, the outer cover  126  and the inner cover  134  are made of a material that does not substantially negatively affect the attenuation of electromagnetic signals passing through the material. In some examples, the outer cover  126  and the inner cover  134  are made of a polymer, such as a fiber-reinforced polymer (e.g., fiberglass), polyvinyl chloride (PVC), nylon, and/or acrylonitrile butadiene styrene (ABS). In some examples, the outer cover  126  and the inner cover  134  are made of the same material. However, in other examples, the outer cover  126  and the inner cover  134  are made of different materials. 
     As shown in  FIGS.  5  and  6   , the heating panel  124  further includes a gasket  138  positioned between, and extending circumferentially about, an outer perimeter of the outer cover  126  and the inner cover  134 . The gasket  138  seals the gap  136  between the outer cover  126  and the inner cover  134  to prevent contaminants, such as moisture, from entering the gap  136 . Additionally, the gasket  138 , extending circumferentially about the outer cover  126  and the inner cover  134 , thus having an annular or circular shape, defines an outer periphery  125  of the heating panel  124  and helps maintain a gap  136  between the outer cover  126  and the inner cover  134  (see, e.g.,  FIG.  6   ). The gasket  138  is made of a compliant material, such as EPDM rubber, in some examples. To promote rigidity and mechanical reinforcement of the heating panel  124 , in some examples, the heating panel  124  includes spacers  188  within the gap  136  and extending from the outer cover  126  to the inner cover  134 . The spacers  188  are spaced apart from each other and provide a load-bearing support that transfers loads between the outer cover  126  and the inner cover  134  to help strengthen the heating panel  124  and maintain the gap  136  between the outer cover  126  and the inner cover  134 . 
     In the illustrated examples, the heating panel  124  has an outer peripheral shape corresponding with an outer peripheral shape of the antenna  102 . For example, the outer cover  126  and the inner cover  134  can be disk-shaped and thus have an outer peripheral shape that is circular. However, in other examples, the outer peripheral shape of the heating panel  124  can be non-circular, such as to correspond with an antenna having a non-circular shape. 
     Referring to  FIGS.  6 - 9   , the heating panel  124  additionally includes heating tracks  150  located in the gap  136 . Each one of the heating tracks  150  includes an electrically-conductive trace  152  and positive temperature coefficient (PTC) elements  130 . The PTC elements  130  of a heating track  150  are electrically connected to the electrically-conductive trace  152  of the heating track  150 . The heating tracks  150  are spaced apart from each other, for example, by a distance D1. Additionally, the PTC elements  130  of each one of the heating tracks  150  are spaced apart from each other along the electrically-conductive trace  162  of the corresponding heating track  150 , for example, by a distance D2. In some examples, the PTC elements  130  are mounted directly to the electrically-conductive traces  152  of the heating tracks  150 . In some examples, the PTC elements  130  are soldered to or adhered (such as via an electrically conductive glue or paste) to the electrically-conductive traces  152 . Also, in certain examples, the spacers  188  are spaced apart from, or do not overlap with, the PTC elements  130 . 
     The heating tracks  150  are affixed to an internally-facing surface  133  of the outer cover  126  or an externally-facing surface  135  of the inner cover  134  (see, e.g.,  FIG.  6   ). As used herein, the term “internally-facing” means facing towards the interior cavity  132  of the antenna  102 , and the term “externally-facing” means facing away from the interior cavity  132  of the antenna  102 , when the antenna heater  110  is mounted to the antenna  102 . In the examples shown in  FIGS.  6 - 9   , the heating tracks  150  are affixed to the internally-facing surface  133  of the outer cover  126 . In such examples, the electrically-conductive traces  152  are affixed onto the internally-facing surface  133  of the outer cover  126  and the PTC elements  130  are mounted onto the electrically-conductive traces  152 , such that for each one of the heating tracks  150 , the electrically-conductive trace  152  is interposed between the PTC elements  130  and the internally-facing surface  133  of the outer cover  126 . However, in other examples, the PTC elements  130  can be affixed to the internally-facing surface  133  of the outer cover  126  and the electrically-conductive traces  152  are applied onto the PTC elements  130 , such that for each one of the heating tracks  150 , the PTC elements  130  are interposed between the electrically-conductive trace  152  and the internally-facing surface  133  of the outer cover  126 . 
     In other examples, the heating tracks  150  are positioned on the inner cover  134 . In some examples, the electrically-conductive traces  152  are affixed onto the externally-facing surface  135  of the inner cover  134  and the PTC elements  130  are mounted onto the electrically-conductive traces  152 , such that for each one of the heating tracks  150 , the electrically-conductive trace  152  is interposed between the PTC elements  130  and the externally-facing surface  135  of the inner cover  134 . However, in other examples, the PTC elements  130  can be affixed to the externally-facing surface  135  of the inner cover  134  and the electrically-conductive traces  152  are applied onto the PTC elements  130 , such that for each one of the heating tracks  150 , the PTC elements  130  are interposed between the electrically-conductive trace  152  and the externally-facing surface  135  of the inner cover  134 . 
     In some examples, when the heating tracks  150  are affixed to the internally-facing surface  133  of the outer cover  126 , the gap  136  of the heating panel  124  provides a thermal barrier that helps direct heat generated by the PTC elements  130  toward and into the outer cover  126 . However, in certain examples, the gap  136  is small enough that either the electrically-conductive traces  152 , the PTC elements  130 , or both are in contact with both the internally-facing surface  133  of the outer cover  126  and the externally-facing surface  135  of the inner cover  134 . 
     In some embodiments, the heating panel  124  includes more than two covers (i.e., more than the inner cover  134  and the outer cover  126 ) while in other embodiments the heating panel  124  may include a single cover and the heating tracks  150  are coupled to the single cover (e.g., the inner surface of the single cover). In some examples, the heating tracks  150  are applied to an internal or external surface of the external cover  116  of the antenna  102 , such that an additional cover is not required. In other examples, a single cover including the heating tracks  150  is applied to the external cover  116  (e.g., the single cover may be adhered to the inner or outer surface of the external cover  116 ). 
     Referring to  FIG.  8   , the electrically-conductive traces  152  of the heating tracks  150  are electrically connected together in parallel. More specifically, corresponding first ends of the electrically-conductive traces  152  are independently electrically connected to the same electrical input line  156 . The electrically-conductive traces  152  are made of copper in some examples. The PTC elements  130  of a given heating track  150  are also connected in parallel via the electrically-conductive trace  152  of the given heating track  150  and a wire  153  of the given heating track  150  (see,  FIG.  9   ). It is noted that the wires  153  are not shown in  FIG.  8    for convenience. Referring to  FIG.  9   , the wire  153  of a given heating track  150  is electrically connected (e.g., soldered) to each one of the PTC elements  130  of the given heating track  150 . Moreover, the ends of the wires  153  of the heating tracks  150  are independently electrically connected to the same electrical output line  158 . In this manner, the electrically-conductive traces  152  are electrically connected directly to the electrical input line  156 , but not electrically connected directly to the electrical output line  158 , and the wires  153  are electrically connected directly to the electrical output line  158 , but not electrically connected directly to the electrical input line  156 . Accordingly, positive current flows to the PTC elements  130 , from the electrical input line  156 , via the electrically-conductive traces  152  and negative current flows from the PTC elements  130 , to the electrical output line  158 , via the wires  153 . 
     The characteristics of the PTC element  130  described below is applicable to all the PTC elements  130  of the antenna heater  110 . The PTC element  130  can have any of various shapes and sizes. In some examples, the PTC element  130  is disk-shaped and has a circular-shaped outer periphery and a height or thickness. In other examples, the PTC element  130  has a non-circular-shaped outer periphery, such as having a rectangular, lozenge, trapezoid, triangular, or other shape, and/or non-planar top and bottom surfaces (e.g., forming a round or oval shape). Additionally, in certain examples, the PTC element  130  is small, such that the PTC elements  130  of one heating track  150  are spaced apart, along the outer cover  126 , from all PTC elements  130  of an adjacent one of the heating tracks  150 . In one example, the PTC element  130  has a maximum dimension (e.g., diameter) between 2 millimeters (mm) and 30 mm, such as 3 mm. Moreover, the PTC element  130  is thin relative to the maximum dimension. For example, the thickness of the PTC element  130  is no greater than 30% of the maximum dimension of the PTC element  130 . The surface of each PTC element  130  facing and affixed to the internally-facing surface  133  of the outer cover  126  has a PTC-element surface area and the internally-facing surface  133  of the outer cover  126  has an outer-cover surface area. In some examples, the PTC-element surface area is about 20 mm 2  and the outer-cover surface area is about 342,119 mm 2 . The PTC-element surface area, the quantity of PTC elements  130 , and the outer-cover surface area are selected such that the PTC elements  130  underlay a desired percentage of the outer cover  126 . The desired percentage corresponds with a desired minimum signal attenuation caused by the PTC elements  130 . In some examples, the percentage of the outer cover  126  underlaid by the PTC elements  130  is between 0.1% and 10.0%, between 0.5% and 5.0%, or between 1.0% and 3.0%. As used herein, the percentage of the outer cover  126  underlaid by the PTC elements  130  corresponds with a ratio of a combined PTC-element surface area (which is equal to a summation of the PTC-element surface area of all the PTC elements  130 ) to the outer-cover surface area of the internally-facing surface  133 . 
     In some examples, the maximum dimension of the PTC element  130  is more than a width of the electrically-conductive trace  152 . However, in other examples, the maximum dimension of the PTC element  130  is less than or equal to the width of the electrically-conductive trace  152 . According to some examples, each one of the electrically-conductive traces  152  has a width of about 4 mm and a thickness of about 100 microns. 
     Each one of the PTC elements  130  is made of a PTC material. In some examples, the PTC material is made of poly-crystalline ceramic materials, such as barium carbonate and titanium oxide, that are highly electrically resistive in an original state, but are made semi-conductive by the addition of dopants, such as tantalum, silica, and manganese. Accordingly, the PTC material of the PTC element  130  can include a combination of poly-crystalline ceramic materials and conductive dopants. In other examples, the PTC material is made of an electrically non-conductive plastic material with embedded conductive grains, such as carbon grains. 
     Generally, the PTC material of the PTC element  130  self-regulates or self-limits the temperature of the PTC element  130 , and thus the antenna heater  110 , by increasing the electrical resistance of the PTC material as the temperature of the PTC material increases. As the temperature approaches an equilibrium temperature, which can be defined as a maximum, transition, or Curie temperature of the PTC material, the electrical resistance of the PTC material “switches” to rapidly increases toward infinite resistance. In some implementations, the equilibrium temperature is defined as the temperature at which the electrical resistance of the PTC material is about twice the resistance as a minimum electrical resistance of the PTC material. The rapid increase in the electrical resistance at the equilibrium temperature rapidly reduces the electrical current allowed to flow through the PTC material. With less current flowing through the PTC material, the temperature of the PTC material correspondingly drops below the equilibrium temperature, which results in a corresponding drop in the electrical resistance of the PTC material and an increase in the current allowed through the PTC material. The increase in current contributes to an increase in the temperature of the PTC material until the equilibrium temperature is again established and the cycle of rapidly increasing the electrical resistance, rapidly decreasing the current, and decreasing the temperature of the PTC material is continued. 
     In the above manner, with the supply of electrical power from an electrical power supply (such as from the power supply  104  via a power cable  112  of the antenna heater  110  (see, e.g.,  FIG.  3   )) at a constant (e.g., unchanging) voltage above an equilibrium voltage, the unique properties of the PTC material allow the PTC material to self-limit its temperature to increase up to but not exceed an equilibrium temperature. Furthermore, because the PTC material self-regulates its temperature, extraneous components and systems for regulating the temperature of antenna heater  110  are not necessary. Although the material of the PTC element  130  has been described as being a PTC material, in some examples, the material of the PTC element  130  be any of various other electrically-conductive materials. 
     According to certain examples, the PTC material of the PTC element  130  has an equilibrium temperature greater than 0° C. Such an equilibrium temperature will ensure that environmental temperatures at or below freezing, the temperature of the PTC elements  130  will remain above freezing. For example, in some implementations, the equilibrium temperature of the PTC element  130  is greater than 10° C. and less than 35° C., such as 19° C. 
     The antenna heater  110  includes multiple heating tracks  150  each including multiple PTC elements  130 . In some examples, the antenna heater  110  includes at least ten heating tracks  150  and between one hundred and three hundred PTC elements  130 . According to one example, the antenna heater  110  includes at least twenty heating tracks  150 . Referring to  FIG.  8   , the electrically-conductive traces  152  of the heating tracks  150  are spaced apart from adjacent ones of the electrically-conductive traces  152  by a first distance D1. Moreover, the PTC elements  130  of a heating track  150  are spaced apart from adjacent ones of the PTC elements  130  along the electrically-conductive trace  152  of the heating track  150  by a second distance D2. Generally, the first distance D1 and the second distance D2 is selected to promote both heating functionality and minimal signal attenuation (e.g., around 1 dB of signal attenuation). In some examples, the first distance D1 is at least 30 mm (e.g., at least 60 mm) and the second distance D2 is at least 30 mm. 
     The first distance D1 is the same as the second distance D2 in some examples, to facilitate a uniform heat distribution of heat generated by the antenna heater  110  in uniform across the heating panel  124 . However, in other examples, the first distance D1 can be smaller than or greater than the second distance D2. Additionally, to promote uniform heating, in some examples, for each heating track  150 , the first distance D1 between adjacent ones of the electrically-conductive traces  152  is the same and/or the second distance D2 between adjacent ones of the PTC elements  130  is the same. But, in other examples, the first distance D1 and/or the second distance D2 can vary such that the distribution of heat generated by the antenna heater  110  is non-uniform across the heating panel  124  if desired. 
     Referring again to  FIG.  3   , the clamp assembly  120  of the antenna heater  110  includes a first clamp arm  120 A and a second clamp arm  120 B. The first clamp arm  120 A and the second clamp arm  120 B are selectively coupled together to surround a majority of the outer periphery  125  of the heating panel  124 . Moreover, when coupled together, the first clamp arm  120 A and the second clamp arm  120 B effectively clamp onto the antenna  102  about the outer ledge  118  of the antenna  102 . Accordingly, the first clamp arm  120 A and the second clamp arm  120 B, when clamped onto the antenna  102 , surround a majority of the outer ledge  118  of the antenna  102 . The first clamp arm  120 A and the second clamp arm  120 B are selectively coupled together via a locking mechanism  122  as will be further explained below. 
     The clamp assembly  120  is configured to clamp onto the antenna  102  and clamp the heating panel  124  to the antenna  102 . In other words, the clamp assembly  120  is configured to simultaneously selectively clamp the heating panel  124  to the antenna  102  as the clamp assembly  120  is clamped to the antenna  102 . Clamping of the clamp assembly  120  onto the antenna  102  is facilitated by engagement between the first clamp arm  120 A and the second clamp arm  120 B with the outer ledge  118  of the antenna  102 . Accordingly, the first clamp arm  120 A and the second clamp arm  120 B are configured to receive and retain the outer ledge  118  of the antenna  102 . Referring to  FIGS.  5  and  6   , the first clamp arm  120 A and the second clamp arm  120 B define channels sized and shaped to receive and retain corresponding portions of the outer ledge  118 . In the illustrated examples, the outer ledge  118  has a substantially U-shaped outer surface. Accordingly, each one of the first clamp arm  120 A and the second clamp arm  120 B has a U-shaped channel  140  that receives a portion of the outer ledge  118  such that the first clamp arm  120 A and the second clamp arm  120 B effectively wrap around or surround the outer ledge  118  when coupled together. When the outer ledge  118  in annular shaped, the first clamp arm  120 A and the second clamp arm  120 B each has a semi-circular shape. In this manner, the first clamp arm  120 A and the second clamp arm  120 B are effectively two equal halves of an annular-shaped clamp. 
     Referring to  FIG.  6   , the U-shaped channel  140  has a width W that is greater than a width of the outer ledge  118 . In this manner, the U-shaped channel  140  is enabled to receive both the outer ledge  118  and the heating panel  124 . In other words, the width W of the U-shaped channel  140  is at least as great as a summation of the width of the outer ledge  118  and a thickness T of the heating panel  124 . Generally, the width of the outer ledge  118  is greater than the thickness T of the heating panel  124 . Accordingly, in some examples, the width W of the U-shaped channel  140  is at least twice a thickness T of the heating panel  124 . 
     The first clamp arm  120 A and the second clamp arm  120 B are selectively engaged with each other to clamp onto the outer ledge  118 . Therefore, the first clamp arm  120 A and the second clamp arm  120 B are movable relative to each other to clamp down onto the outer ledge  118 . As shown in  FIG.  10   , each one of the first clamp arm  120 A and the second clamp arm  120 B includes a first end portion  121  and a second end portion  127 , which is opposite the first end portion  121 . Engagement between the first clamp arm  120 A and the second clamp arm  120 B includes intercoupling of the first end portions  121  of the first clamp arm  120 A and the second clamp arm  120 B and intercoupling of the second end portions  127  of the first clamp arm  120 A and the second clamp arm  120 B. In some examples, intercoupling at the first end portions  121  and the second end portions  127  is facilitated by respective locking mechanisms  122  located at the first end portions  121  and the second end portions  127 . The locking mechanisms  122  can be the same such that the first end portions  121  and the second end portions  127  are intercoupled in the same way. 
     However, in other examples, the locking mechanisms  122  are different such that the first end portions  121  and the second end portions  127  are intercoupled in different ways. For example, as shown in  FIG.  10   , the first end portions  121  of the first clamp arm  120 A and the second clamp arm  120 B are intercoupled via a swivel bracket  123 , which enables the first end portions  121  to swivel relative to each other while remaining coupled to each other, and the second end portions  127  of the first clamp arm  120 A and the second clamp arm  120 B are intercoupled via a lock (e.g., a locking clamp), which enables the second end portions  127  to be selectively locked together. Referring to  FIG.  12   , in some examples, the lock includes a first-clamp-arm lock portion  122 A (e.g., a latch) at the second end portion  127  of the first clamp arm  120 A and a second-clamp-arm lock portion  122 B (e.g., a hook) at the second end portion  127  of the second clamp arm  120 B. The first-clamp-arm lock portion  122 A and the second-clamp-arm lock portion  122 B are engageable to selectively lock together the second end portions  127  of the first clamp arm  120 A and the second clamp arm  120 B. 
     To aid in installation of the antenna heater  110  onto the antenna  102 , in some examples, the heating panel  124  is fixed to the first clamp arm  120 A such that the heating panel  124  does not move relative to the first clamp arm  120 A. The antenna heater  110  is adhered or fastened to the first clamp arm  120 A in certain examples. More specifically, the heating panel  124  can be inserted into the U-shaped channel  140  of the first clamp arm  120 A and adhesively fixed or fastened in place. In this manner, the clamp assembly  120  and the heating panel  124  can be moved together as a single unit, which enables a single technician to handle and manipulate the antenna heater  110 . 
     Referring to  FIG.  11   , in some examples, the clamp assembly  120  further includes padding  160  located within the U-shaped channel  140  of one or both of the first clamp arm  120 A and the second clamp arm  120 B. The padding  160  is compliant and deforms against the heating panel  124  as the second clamp arm  120 B is moved to receive the heating panel  124  within the U-shaped channel  140  of the second clamp arm  120 B. The padding  160  promotes a seal against the heating panel  124  and helps to prevent damage to the heating panel  124  as the second clamp arm  120 B is moved to receive the heating panel  124 . 
     According to some examples, the antenna heater  110  is coupled to (e.g., installed onto) the antenna  102  by moving the antenna heater  110  relative to the antenna  102  such that the first clamp arm  120 A (e.g., upper clamp arm) is above the outer ledge  118  of the antenna  102  (see, e.g.,  FIG.  10   ). Then, the antenna heater  110  is lowered such that the outer ledge  118  is received into the U-shaped channel of the first clamp arm  120 A and the first clamp arm  120 A rests on the outer ledge  118  (see, e.g.,  FIG.  11   ). Because the antenna  102  supports the antenna heater  110  in this position, a technician need not continue to lift the antenna heater  110 . The second clamp arm  120 B (e.g., lower clamp arm) can then be pivoted relative to the first clamp arm  120 A and raised to receive the outer ledge  118  into the U-shaped channel  140  of the second clamp arm  120 B (see, e.g.,  FIG.  12   ). When the outer ledge  118  is fully received in the U-shaped channel  140  of the second clamp arm  120 B, the first-clamp-arm lock portion  122 A and the second-clamp-arm lock portion  122 B can be engaged to lock the second clamp arm  120 B to the first claim arm  120 A. 
     Because the heating panel  124  is non-movably fixed to the first clamp arm  120 A, as the first clamp arm  120 A is lowered to receive the outer ledge  118 , the heating panel  124  is moved over and covers the external cover  116  of the antenna  102 . Accordingly, the heating panel  124  can be positioned in front of the external cover  116  and the outer ledge  118  can be inserted into the first clamp arm  120 A with one motion. In some examples, the heating panel  124  is positioned flush against the external cover  116  when the outer ledge  118  is received within the U-shaped channel  140 . Again, because the antenna heater  110  is movable as a single unit, and supportable on the outer ledge  118  of the antenna  102 , the process of installing the antenna heater  110  on an antenna  102 , whether in the field on an existing antenna or in the factory, prior to installing the antenna in the field, can be performed by a single technician in a simple, safe, and efficient manner. 
     In view of the foregoing, it is recognized that the heating panel  124  can be mounted to the antenna  102  in ways other than with the clamping assembly  120 . For example, the heating panel  124  can be adhered to or otherwise fastened to the antenna  102 , whether in the factory, prior to installing the antenna  102  in the field, or after the antenna  102  has been installed in the field. In some examples, the heating panel  124  is permanently or removably coupled to the antenna  102  in the factory as part of the original equipment of the antenna  102 . In some examples, the antenna  102  does not include an external cover  116 , a backing layer  117 , or both an external cover  116  and a backing layer  117 . In such examples, the heating panel  124  acts as the external cover  116  to protect the antenna  102  from debris and to perform the heating function described herein. In such examples, the heating panel  124  may be permanently or removably coupled to the antenna  102 . In other examples, the external cover  116 , the backing layer  117 , or both the external cover  116  and the backing layer  117  are modified to accommodate the heating panel  124  or to account for the protection provided by the heating panel  124  (for example, the external cover  116 , the backing layer  117 , or both the external cover  116  and the backing layer  117  may have a reduced thickness and/or strength in view of the additional protection provided by the heating panel  124 ). 
     Once installed, the antenna heater  110  can be actively controlled, based on environmental conditions, to heat the antenna  102  and prevent the formation of ice on the external cover  116  of the antenna  102 . Referring to  FIG.  13   , an antenna system  100 , according to one example, is shown. The antenna system  100  includes the antenna  102 , the power supply  104 , and the antenna heater  110  (e.g., at least one of the PTC elements  130  of the antenna heater  110 ). The antenna system  100  further includes an antenna heater system  106  that includes a temperature sensor  180 , a humidity sensor  182 , a control module  184 , and the antenna heater  110 . The temperature sensor  180  is located and configured to detect the temperature of air external to the antenna heater  110 , such as proximate the antenna  102 . The humidity sensor  182  is located and configured to detect the humidity (e.g., relative humidity) of air external to the antenna heater  110 , such as proximate the antenna  102 . 
     The control module  184  includes computer processing capability and control to supply electrical power to the electrically-conductive traces  152  of the heating tracks  150 , via the electrical input line  156 . As electrical current flows through the electrically-conductive traces  152 , the PTC elements  130  of the heating tracks  150  begin to increase in temperature and generate heat  186 . The heat  186  generated by the PTC elements  130  is transferred to the outer cover  126  to heat the outer cover  126 . The electrically-conductive trace  152  of each heating track  150 , in addition to providing an electrical connection for the PTC elements  130  of the heating track  150 , also help to transfer heat from the PTC elements  130  to the outer cover  126 . 
     As electrical current continues to flow through the electrically-conductive traces  152 , the temperature of and the heat generated by the PTC elements  130  continues to increase. As long as electrical current flows, the temperature and heat generated by the PTC elements  130  will continue to increase until a temperature of the PTC elements  130  reaches the equilibrium temperature of the PTC material of the PTC elements  130 , at which time the PTC material of the PTC elements  130  will stabilize at an equilibrium temperature based on the power input and thermal dissipation being experienced. In this manner, the PTC elements  130  self-regulate their temperature and the amount of heat generated thereby. 
     Ambient conditions have an effect on the characteristics and behavior of the PTC material of the PTC elements  130 . More specifically, as shown in  FIGS.  15 A- 15 C , different ambient conditions can affect the current-voltage, the resistance-temperature, and the power-voltage characteristics of the PTC material. In this context, power is defined as heater power. Four ambient conditions, Amb1, Amb2, Amb3, and Amb4, are represented in  FIGS.  15 A- 15 C . Amb1 represents ambient conditions having a relatively high ambient temperature and static airflow. In contrast, Amb4 represents ambient conditions having a relatively low ambient temperature and a relatively high airflow. Amb2 represents ambient conditions having an ambient temperature lower than Amb1 and higher than Amb4, and airflow higher than Amb1 and lower than Amb4. Amb3 represents ambient conditions having an ambient temperature lower than Amb2 and higher than Amb4, and airflow higher than Amb2 and lower than Amb4. Points A-D are equilibrium operating points for the four ambient conditions Amb4, Amb3, Amb2, and Amb1, respectively. As shown in  FIG.  15 B , in most conditions, the equilibrium temperature of the PTC material is fairly constant. This is because the resistance-temperature characteristic of PTC material is very steep (e.g., up to 30%/° C. above the equilibrium temperature in certain examples). In other words, above the equilibrium temperature, a small deviation in the operating temperature of the PTC material results in a large change in the resistance of the PTC material. This phenomenon of PTC materials enables PTC materials to be very effective at self-regulation of its temperature, which is further evidenced by the relatively large differences in heater power (at a given voltage) for the different ambient conditions. 
     Additionally, the PTC material enables the antenna heater  110  to promote uniform heating across the antenna heater  110  despite differences in ambient condition across the ambient heater  110 , such as when the surface of the antenna heater  110  experiences variable airflow. When ambient conditions across the ambient heater  110  vary, some PTC elements  130  within a localized region of the ambient heater  110  will draw more current relative to PTC elements  130  in other regions of the ambient heater  110  to promote a constant temperature across all regions of the ambient heater  110 . 
     Moreover, as disclosed above, the PTC material of the PTC elements  130  can be selected to have an equilibrium temperature that is sufficiently high (e.g., at least 0° C.) such that snow accumulation and/or ice formation is prevented. Accordingly, the control module  184  is simply required to turn a constant supply of electrical current on and off to maintain the temperature of the PTC elements  130  at a constant temperature and the heat generated by the PTC elements  130  at a constant level. 
     The control module  184  turns the electrical current (e.g., electrical power) on or off based on the temperature and the humidity detected by the temperature sensor  180  and the humidity sensor  182 , respectively. More specifically, the control module  184  enables the supply of electrical current to the electrically-conductive traces  152  only when the temperature of the air detected by the temperature sensor  180  is below a temperature threshold and the relative humidity of the air detected by the humidity sensor  182  is above a humidity threshold. The temperature threshold and the humidity threshold correspond with temperatures and humidity levels conducive to the formation of ice. Accordingly, when the temperature and humidity of air are not conducive to the formation of ice, which means the formation of ice on the antenna  102  is not likely, no electrical current is supplied because heat from the PTC elements  130  is not necessary to prevent the formation of ice. However, when the temperature and humidity of air are conducive to the formation of ice, the control module  184  supplies electrical current to generate heat from the PTC elements  130  and prevent the formation of ice. In certain examples, the temperature threshold is between 1° C. and 10° C., such as 7° C., and the humidity threshold is between 50% and 100%, such as 55%. 
     According to some examples, the control module  184  is further configured to continuously increase a current of the electrical power from zero to a maximum current over a predetermined time interval in response to the temperature of the air detected by the temperature sensor  180  being below the temperature threshold and the relative humidity of the air detected by the humidity sensor  182  being above the humidity threshold. In certain examples, the antenna heater  110  relies on the electrical power supplied to the antenna  102  for supplying the electrical current to the electrically-conductive traces  162  of the antenna heater  110 . Such power is supplied at a constant voltage, such as 48 V. Ramping up the electrical current helps prevent an inrush of current, which may occur with such a constant voltage and such a high number of electrically resistive elements (e.g., the PTC elements  130 ) in the circuit and which can damage the electrical components of the antenna heater  110 . 
     Referring to  FIG.  14   , according to some examples, a method  200  of preventing ice formation on the antenna  102  includes (block  202 ) mounting the antenna heater  110  to the antenna  102 . The method  200  also includes (block  204 ) activating the antenna heater  110  to supply heat to the antenna  102  only when air, around the antenna  102 , has a temperature below a temperature threshold and has a relative humidity above a humidity threshold. Mounting the antenna heater  110  to the antenna  102  can include clamping the heating panel  124  onto the hollow base  114  such that the heating panel  124  covers the external cover  116 . Clamping the heating panel  124  onto the hollow base  114  can include receiving a first portion of the outer ledge  118  of the antenna  102  into the U-shaped channel  140  (i.e., first-clamp-arm channel) of the first clamp arm  120 A, receiving a second portion of the outer ledge  118  of the antenna  102  into the U-shaped channel  140  (i.e., second-clamp-arm channel) of the second clamp arm  120 B, and, when the first portion of the outer ledge  118  is received into the first-clamp-arm channel and the second portion of the outer ledge  118  is received into the second-clamp-arm channel, locking together the first clamp arm  120 A and the second clamp arm  120 B. In one example, the heating panel  124  is moved into position over the external cover  116  of the antenna  102  as the first portion of the outer ledge  118  is received into the first-clamp-arm channel. Activating the antenna heater  110  can include heating the PTC elements  130  of the antenna heater  110  up to the equilibrium temperature of the PTC material of the PTC elements  130 . 
     In the above description, certain terms may be used such as “up,” “down,” “upper,” “lower,” “horizontal,” “vertical,” “left,” “right,” “over,” “under” and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an “upper” surface can become a “lower” surface simply by turning the object over. Nevertheless, it is still the same object. Further, the terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise. Further, the term “plurality” can be defined as “at least two.” Moreover, unless otherwise noted, as defined herein a plurality of particular features does not necessarily mean every particular feature of an entire set or class of the particular features. 
     Additionally, instances in this specification where one element is “coupled” to another element can include direct and indirect coupling. Direct coupling can be defined as one element coupled to and in some contact with another element. Indirect coupling can be defined as coupling between two elements not in direct contact with each other, but having one or more additional elements between the coupled elements. Further, as used herein, securing one element to another element can include direct securing and indirect securing. Additionally, as used herein, “adjacent” does not necessarily denote contact. For example, one element can be adjacent another element without being in contact with that element. 
     As used herein, the phrase “at least one of”, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, “at least one of” means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, “at least one of item A, item B, and item C” may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, “at least one of item A, item B, and item C” may mean, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination. 
     Unless otherwise indicated, the terms “first,” “second,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, e.g., a “second” item does not require or preclude the existence of, e.g., a “first” or lower-numbered item, and/or, e.g., a “third” or higher-numbered item. 
     As used herein, a system, apparatus, structure, article, element, component, or hardware “configured to” perform a specified function is indeed capable of performing the specified function without any alteration, rather than merely having potential to perform the specified function after further modification. In other words, the system, apparatus, structure, article, element, component, or hardware “configured to” perform a specified function is specifically selected, created, implemented, utilized, programmed, and/or designed for the purpose of performing the specified function. As used herein, “configured to” denotes existing characteristics of a system, apparatus, structure, article, element, component, or hardware which enable the system, apparatus, structure, article, element, component, or hardware to perform the specified function without further modification. For purposes of this disclosure, a system, apparatus, structure, article, element, component, or hardware described as being “configured to” perform a particular function may additionally or alternatively be described as being “adapted to” and/or as being “operative to” perform that function. 
     The schematic flow chart diagrams included herein are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of one example of the presented method. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Additionally, the format and symbols employed are provided to explain the logical steps of the method and are understood not to limit the scope of the method. Although various arrow types and line types may be employed in the flow chart diagrams, they are understood not to limit the scope of the corresponding method. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown. 
     The present subject matter may be embodied in other specific forms without departing from its spirit or essential characteristics. The described examples are to be considered in all respects only as illustrative and not restrictive. Examples of the scope of the present subject matter can be found in the following claims.