Patent Publication Number: US-8537061-B2

Title: System and apparatus for locomotive radio communications

Description:
FIELD 
     The subject matter disclosed herein relates to an apparatus for locomotive radio communications. 
     BACKGROUND 
     A locomotive or other rail vehicle may be equipped with a radio communication system including a radio in a cab of the locomotive and an antenna mounted on a roof of the locomotive. The radio communication system may include one or more radios using one or more antennas, such as when transmitting and receiving voice and data communications with different radios. The configuration of radio communication systems may change during the lifetime of a locomotive due to technological or regulatory concerns. For example, the radio communication system may be regulated by a governmental agency and the regulations may change. As another example, it may be desirable to add a new radio and/or antenna as radio technology improves or if new radio spectrum becomes available. Thus, radios and their associated antennas may be added and/or removed during the lifetime of the locomotive. One solution for adding an antenna to a locomotive includes finding a suitable location for the antenna on the roof of the locomotive, drilling an access hole in the roof, running cable from the antenna to the radio, and securely fastening the antenna to the roof of the locomotive. This solution may be time consuming and costly due to labor costs and non-productive maintenance time of the locomotive. In addition, the mounting area of the antenna may be subject to water intrusion, which may result in damaged equipment and/or require further maintenance time. 
     BRIEF DESCRIPTION OF THE INVENTION 
     An apparatus for locomotive radio communications is provided for removably electrically connecting antennas to a roof of the locomotive. In one embodiment, the radio communication system comprises a removable antenna platform and an antenna interface bulkhead connected to the roof of the locomotive. The antenna platform includes a first blind mate connector connected to an antenna mount. The antenna mount is connected to a ground plane. The antenna interface bulkhead includes a second blind mate connector configured to mate with the blind mate connector of the antenna platform when the antenna platform is attached to the antenna interface bulkhead. The antenna interface bulkhead and antenna platform are configured to attach to one another in one orientation only. Thus, one or more antennas may be quickly attached to or removed from the roof of the locomotive, reducing maintenance time for the locomotive when an antenna upgrade may be desired. In addition, water intrusion may be reduced by reducing the number of holes in the roof of the locomotive and by forming a water resistant seal at the antenna interface bulkhead. 
     This brief description is provided to introduce a selection of concepts in a simplified form that are further described herein. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure. Also, the inventor herein has recognized any identified issues and corresponding solutions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below: 
         FIG. 1  shows an example embodiment of a locomotive including an antenna platform mounted on the roof of the locomotive. 
         FIG. 2  shows a view of an example embodiment of the antenna platform including an antenna dome. 
         FIG. 3  shows a view of an example embodiment of the antenna platform with the antenna dome removed. 
         FIG. 4  shows an example embodiment of wiring of antennas to an antenna interface of the antenna platform. 
         FIG. 5  shows an example embodiment of the antenna interface of the antenna platform. 
         FIG. 6  shows an example embodiment of an antenna interface bulkhead and mounting hardware for connecting the antenna platform to the roof of the locomotive and the antenna interface bulkhead. 
         FIG. 7  shows a schematic cross-section of an example embodiment of an antenna platform attached to a locomotive. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example embodiment of a vehicle, specifically, a rail vehicle such as a locomotive, comprising a radio communication system including one or more radios using one or more antennas. An antenna may be mounted on a common antenna platform which may be attached to a roof of the locomotive. The antenna may be connected to a radio in a cab of the locomotive by an antenna interface mounted to the roof of the locomotive. The antenna platform may include an antenna dome that may protect the antenna and the antenna interface from the environment.  FIG. 2  shows a view of an example embodiment of the antenna platform including an antenna dome.  FIG. 3  shows a view of an example embodiment of the antenna platform with the antenna dome removed. The antenna platform may include a plurality of antennas that are connected to an antenna interface.  FIG. 4  shows an example embodiment of cabling between antennas and the antenna interface, and  FIG. 5  shows an example embodiment of the antenna interface. The antenna interface may be used to connect the antenna platform to an antenna interface bulkhead on the roof of the locomotive.  FIG. 6  shows an example embodiment of the antenna interface bulkhead and mounting hardware for connecting the antenna platform to the antenna interface bulkhead. In this manner, the antenna platform may enable a modular and reconfigurable platform for mounting one or more antennas on the roof of a rail vehicle, such as illustrated in the example embodiment of  FIG. 7 . The antenna platform may be installed faster than individual antennas may be installed on the roof, and the antenna platform may provide less opportunity for water to intrude through the roof of the locomotive compared to individual antennas. Thus, installing the antenna platform may result in less maintenance time of the locomotive compared to installing individual antennas. 
       FIG. 1  illustrates an example embodiment of a rail vehicle, herein depicted as locomotive  100 . Locomotive  100  may comprise a cab  120  for housing an operator, controls, and electronics that are to be shielded from the elements. Locomotive electronics may include a controller  150  and a radio communication system  110  including a radio  140 , an antenna (not shown in this figure), and an optional signal hub  160 . Signal hub  160  may be used as a multiplexor to route signals between a radio and an antenna, or signal hub  160  may be used as a signal splitter, such as when more than one antenna is used to transmit a signal from a radio. Signal hub  160  may be controlled by controller  150  or by the locomotive operator. 
     Radio communication system  110  may include one or more radios using one or more antennas. Each radio and each antenna may be tuned to operate at a range of frequencies. A radio may include a receiver for receiving radio signals and/or a transmitter for transmitting radio signals. In one embodiment, radio communication system  110  may include a radio, such as radio  140 , and an antenna for two-way voice communications between the locomotive operator and a control center of a railroad. For example, voice communications may be transmitted and received by a radio centered at a 220 MHz frequency in the very high frequency (VHF) band. As another example, voice communications may be transmitted and received by a radio using the 800 MHz and/or 1900 MHz frequency bands, such as used for cellular communications. In another example, multiple radios may be used to provide redundant communications channels. 
     In one embodiment, radio communication system  110  may include a radio and an antenna for data communications. The data communications may be between locomotive  100  and a control center of a railroad, another locomotive, a satellite, and/or a wayside device, such as a railroad switch. For example, locomotive  100  may be in communication with a second locomotive that is coupled with locomotive  100 . Locomotives may exchange operational parameters, such as engine speed, engine temperature, and fuel level, for example. The 802.11 wireless standard may provide an inexpensive communication protocol for communicating with a device in close proximity, such as a coupled locomotive. Thus, radio communication system  110  may include an 802.11 radio and an antenna for receiving signals centered at 2450 MHz (which is the designated frequency for the 802.11 standard). Data communications between more remote devices may be transmitted and received by a radio in the VHF band or by a cellular radio using the 800 MHz and/or 1900 MHz frequency bands, for example. In one embodiment, locomotive  100  may include a Global Positioning System (GPS) receiver and an antenna for receiving signals centered at 1575.42 MHz and/or other designated GPS frequencies. 
     In one example, locomotive  100  comprises a controller  150  that may include a computer control system. The locomotive control system may further comprise computer readable storage media including code for enabling an on-board monitoring of locomotive operation. Controller  150 , overseeing locomotive systems control, communications, and management, may be configured to receive signals from a variety of sensors in order to estimate locomotive operating parameters. For example, controller  150  may estimate geographic coordinates of locomotive  100  using signals from a GPS receiver. As another example, controller  150  may estimate the speed of locomotive  100  from a speed sensor. Controller  150  may control an engine of locomotive  100 , in response to operator input, by sending a command to various engine control hardware components such as inverters, alternators, relays, fuel injectors, fuel pumps, etc. (not shown). 
     In one embodiment, controller  150  may include instructions for implementing a positive train control (PTC) system. The PTC system may be used for monitoring and controlling locomotive  100  in a desired manner. For example, wayside signal information may be communicated from a wayside device to locomotive  100 . Under some circumstances, such as if locomotive  100  is being operated in an undesired manner, the PTC system may automatically control locomotive  100  by overriding operator control of locomotive  100 . In one example, the PTC system may maintain the speed of locomotive  100  within a speed limit for a section of track. The speed limit may be communicated from a wayside device or the speed limit may be determined based on a geographic location of locomotive  100 . The PTC system may determine the geographic location of locomotive  100  from GPS data received by the GPS receiver. The geographic location may be used as an index to a database to determine a speed limit associated with the geographic location. The database may be stored locally on controller  150  or the database may be stored on a remote server and accessed by sending requests and receiving responses through radio communication system  110 . Controller  150  may compare the estimated speed of locomotive  100  to the speed limit of the section of track at the geographic location. If the estimated speed exceeds the speed limit, the PTC system may apply a brake of locomotive  100  or reduce a throttle setting to maintain a reduced speed for locomotive  100 . 
     It may be desirable for a locomotive with a PTC system to have multiple upgradeable radios and antennas. For example, redundant communication channels may be desirable so that time sensitive information may be delivered to the PTC system in a timely manner, even when a radio fails or is out of range of a signal. As another example, it may be desirable to add and/or upgrade radios and antennas due to changing governmental regulations and/or advances in radio technology. 
     An antenna platform  130  may be used to attach one or more antennas to locomotive  100 . For example, antenna platform  130  may include a mounting plate  134  for attaching antenna platform  130  to a roof  122  of locomotive  100 . Roof  122  may be constructed of a conductive metal, such as steel, and may be part of (or at least electrically connected to) a chassis of locomotive  100 . In one example, an antenna may be mounted on antenna platform  130  instead of attaching the antenna directly to roof  122 . Antenna platform  130  may include an area for mounting multiple antennas and an antenna interface for connecting each antenna to cables in cab  120  of locomotive  100 . The antennas and the antenna interface may be shielded by an antenna dome  132  from the elements. 
     Antenna platform  130  may be quickly detached from locomotive  100 , as detailed herein, to perform maintenance and/or to add antennas and/or to upgrade antennas.  FIG. 2  illustrates an example embodiment of antenna platform  130  that may be detached from locomotive  100 . Antenna platform  130  includes mounting plate  134  and antenna dome  132 . Antenna dome  132  may be suitably shaped to cover the antennas and the antenna interface on roof  122 . Antenna dome  132  may be water resistant and transmissive to radio waves at the frequencies received and transmitted by the antennas. In one example, antenna dome  132  may be transmissive to radio waves from the lower end of the VHF band (30 MHz) to the upper end of the SHF band (30 GHz). In another example, antenna dome  132  may be transmissive to radio waves from 150 MHz to 3 GHz. As a non-limiting example, antenna dome  132  may be constructed from plastic, fiberglass, or other suitable material. In one embodiment, a watertight gasket may be inserted between antenna dome  132  and mounting plate  134  to resist water intrusion. For example, the watertight gasket may extend around a periphery of antenna dome  132 . 
     Mounting plate  134  may include an electrically conductive material that is electrically connected to a ground of locomotive  100  through the chassis of locomotive  100 , by way of the roof  122  or otherwise. Thus, mounting plate  134  may utilize roof  122  of locomotive  100  to establish an efficient counterpoise for the antennas of antenna platform  130 . In one embodiment, mounting plate  134  may be unpainted or have unpainted surfaces to increase ground integrity. Mounting plate  134  may include holes, such as holes  210   a ,  210   b , and  210   c , for inserting fasteners, such as bolts, to attach antenna platform  130  to locomotive  100 . In one example, six holes may be used for attaching antenna platform  130  to locomotive  100 . Decreasing the attachment points may increase the speed at which a maintenance technician may remove antenna platform  130 . Increasing the attachment points may increase the coupling strength of antenna platform  130  to locomotive  100 . In one embodiment, bolts inserted into holes of mounting plate  134  may attach mounting plate  134  to locomotive  100  and antenna dome  132  to mounting plate  134 . 
       FIG. 3  illustrates an example embodiment of antenna platform  130  with antenna dome  132  removed. An antenna platform may include an antenna interface and an antenna rail for mounting one or more antennas. In one embodiment, antenna platform  130  includes antenna interface  360 , antenna rails  310  and  312 , and antennas  320 ,  322 ,  330 ,  332 ,  340 , and  342 . In one embodiment, antenna platform  130  includes two antenna rails. However, alternative embodiments of antenna platform  130  may include more or fewer antenna rails. In one embodiment, antenna rails  310  and  312  may each include antenna mounts for three antennas. Thus, in one embodiment, antenna platform  130  may include at least six antenna mounts. However, more or fewer antennas may be mounted on each antenna rail. In another embodiment, antenna platform  130  may include at least four antenna mounts. The number of antenna rails and the number of antennas mounted on each rail may be determined based on the desired number of antennas for radio communication system  110  and/or the desired weight and/or size of antenna platform  130 . For example, the number of radios and the communication protocols supported by radio communication system  110  may determine the number of antennas included on antenna platform  130 . 
     In one embodiment, antenna rail  310  may include an NMO mount for connecting each antenna. An NMO mount provides a standard attachment interface (having a 1⅛ inch 18-pitch threaded connector) and may enable an antenna to be attached to antenna rail  310  by screwing the antenna to the NMO mount. Similarly, an antenna may be removed by unscrewing the antenna from the NMO mount of antenna rail  310 . Thus, an antenna may be added to or removed from antenna platform  130  quickly and with a minimal set of tools. In one embodiment, an antenna may include a waterproof gasket to reduce water intrusion at the base of the antenna when the antenna is attached to the NMO mount. In alternative embodiments, UHF, BNC, or other suitable mounts may be used for mounting antennas and/or the antennas may be directly mounted, such as by soldering, to antenna rail  310 . 
     Antenna rail  310  may include a conductive material and be electrically connected to a radio frequency (RF) ground. For example, antenna rail  310  may be electrically connected to mounting plate  134  which may be electrically connected to the chassis of locomotive  100 . In this manner, antenna rail  310  may act as a ground plane for the antennas connected to antenna rail  310 . In one example, antenna rail  310  may be plated with an electrically conductive material. Antenna rail  310  may include an unpainted surface around each antenna mounting surface and at the interface to mounting plate  134  to ensure ground integrity. In one embodiment, an antenna rail may be integral to mounting plate  134 . Thus, a mounting plate may include one or more antenna mounts. Each antenna mount is terminated to an interconnect cable, such as cables  350  and  352 , which provides a transmission path to antenna interface  360 . 
     The width of antenna interface  360  and the spacing between antenna mounting points may provide physical separation between different antennas attached to antenna platform  130 . For example, spatial diversity may be used to increase the quality of a received or transmitted signal. Spatial diversity may be employed when two or more similar antennas are physically separated by at least one wavelength of the frequency being received or transmitted. In one embodiment, spatial diversity may be enabled by spacing the antenna mounts at least one wavelength apart. In an alternate embodiment, spatial diversity may be realized by spacing the antenna mounts between one wavelength and four wavelengths apart. The wavelength of an electromagnetic or radio wave is inversely proportional to the frequency of the radio wave. Thus, higher frequency antennas may be placed closer to each other than lower frequency antennas. 
     In an embodiment, antennas  340  and  342  are 802.11 antennas. The 802.11 antennas  340  and  342  operate at a central frequency of 2450 MHz having a wavelength of 4.8 inches. Thus, 802.11 antennas  340  and  342  may be separated by more than 4.8 inches. In one embodiment, 802.11 antennas  340  and  342  may be installed on the antenna mounts closest to antenna interface  360  and distance  370  (the distance between the 802.11 antennas  340  and  342 ) may be greater than five inches. In an alternate embodiment, 802.11 antennas  340  and  342  may be installed on the antenna mounts closest to antenna interface  360  and distance  370  may be greater than five inches and less than eighteen inches. However, spatial diversity may be enabled if 802.11 antennas  340  and  342  are installed on any of the antenna mounts that are separated by more than 4.8 inches. In one embodiment 802.11 antennas  340  and  342  may have a fifty ohm characteristic impedance. 
     In an embodiment, antennas  330  and  332  are cell antennas. Each cell antenna  330  and  332  may receive and transmit frequencies at 1900 MHz and/or 800 MHz. The wavelengths of 1900 MHz and 800 MHz radio waves are 6.2 inches and 14.8 inches, respectively. Thus, cell antennas  330  and  332  may be separated by more than 14.8 inches. In one embodiment, cell antennas  330  and  332  may be installed on the antenna mounts in the middle of antenna rails  310  and  312 , respectively, and distance  380  (the distance between the cell antennas  330  and  332 ) may be greater than fifteen inches. In an alternate embodiment, cell antennas  330  and  332  may be installed on the antenna mounts in the middle of antenna rails  310  and  312 , respectively, and distance  380  may be greater than fifteen inches and less than twenty-four inches. In one embodiment cell antennas  330  and  332  may have a fifty ohm characteristic impedance. 
     In an embodiment, antenna  320  is a VHF antenna. VHF antenna  320  may receive and transmit frequencies at 220 MHz with a wavelength of 53.6 inches. Thus, multiple VHF antennas may be separated by more than fifty-four inches. In one embodiment, VHF antenna  320  may be installed on an antenna mount farthest from antenna interface  360 . For example, VHF antenna  320  may be installed on the antenna mount of antenna rail  310  farthest from antenna interface  360 . In one embodiment, distance  390  (the distance from the VHF antenna  320  to the opposite side of the platform  130 ) may be greater than or equal to fifty-four inches and a second VHF antenna may be installed on the antenna mount of antenna rail  312  farthest from antenna interface  360 . However, it may be desirable to decrease a width of mounting plate  134  to reduce the weight, cost, or wind-load of antenna platform  130 . Thus, in one embodiment, distance  390  may be greater than fifteen inches and less than fifty-four inches. Spatial diversity may be enabled for the VHF frequency by adding a second VHF antenna spaced more than fifty-four inches from antenna platform  130 . For example, locomotive  100  may include multiple antenna platforms or a VHF antenna may be separately mounted on roof  122 . In alternate embodiments, there may be a single VHF antenna and spatial diversity will not be enabled for VHF frequencies. In one embodiment VHF antenna  320  may have a fifty ohm characteristic impedance. 
     In another embodiment, antenna  322  is a GPS antenna. GPS antenna  322  receives frequencies at a central frequency of 1575.42 MHz with a wavelength of 7.5 inches. Thus, multiple GPS antennas may be separated by more than 7.5 inches. In one embodiment, GPS antenna  322  may be installed on an antenna mount farthest from antenna interface  360 . For example, GPS antenna  322  may be installed on the antenna mount of antenna rail  312  farthest from antenna interface  360 . If spatial diversity is desired for receiving GPS, locomotive  100  may include multiple antenna platforms or a GPS antenna may be separately mounted on roof  122 , for example. In one embodiment GPS antenna  322  may have a fifty ohm characteristic impedance. 
     By including antenna mounts at suitable spacings, antenna platform  130  may reduce or prevent errors compared to technicians manually installing antennas. For example, a technician manually installing antennas on roof  122  may inadvertently install antennas too close to enable spatial diversity, especially for the longer wavelength antennas, such as the VHF antenna. However, antenna platform  130  may include predefined spacings between each antenna mount reducing the likelihood of an error by a technician installing an antenna. 
     Signals received by an antenna may be transmitted to a radio. Similarly, signals generated by a radio may be transmitted by an antenna. The signal to noise ratio of a signal may be increased when the loss through the transmission path between the radio and the antenna is decreased. Transmission loss may be reduced when the characteristic impedance of the antennas, cables, and connectors in the transmission path are matched, such as when each component has a characteristic impedance of fifty ohms, for example. In one embodiment, the transmission path may include a cable between the antenna and antenna interface  360 , antenna interface  360 , an antenna interface bulkhead, and a cable between the antenna interface bulkhead and radio  140 . Antenna interface  360  and the antenna interface bulkhead may form a blind mate connection when antenna platform  130  is attached to locomotive  100 . The blind mate connection may provide a low loss transmission path and enable antenna platform  130  to be quickly installed on or removed from locomotive  100 .  FIGS. 4-6  show aspects of the transmission path between antennas and radios that may reduce losses and enable quick installation and/or removal of antenna platform  130 . Specifically,  FIG. 4  shows connectors and cables from antennas to antenna interface  360 .  FIG. 5  shows cables connecting to a front side of antenna interface  360 .  FIG. 6  shows connectors on a back side of antenna interface  360  and a roof side of the antenna interface bulkhead. The connectors on the back side of antenna interface  360  join, or mate, with connectors of the antenna interface bulkhead to form a blind mate connection when antenna platform  130  is attached to locomotive  100 . 
     Returning to the figures,  FIG. 4  illustrates an example embodiment of a back side of antenna rail  312  showing cabling between antennas and antenna interface  360 . Antenna rail  312  may include antenna mounts  422 ,  432 , and  442  for attaching antennas  322 ,  332 , and  342 , respectively. In one embodiment, each of antenna mounts  422 ,  432 , and  442  may be an NMO mount including an M-type mount for connecting the antenna and an SMA connector for attaching to a cable. Cables  352   a ,  352   b , and  352   c  provide a transmission path for signals from antennas  322 ,  332 , and  342 , respectively, to antenna interface  360 . Cables  352   a ,  352   b , and  352   c  may be routed along the back side of antenna rail  312  to an exit point  450  of antenna rail  312  and then to antenna interface  360 . Each of the cables may be clipped to the back side of antenna rail  312  with clips, such as clip  410 , for example. Clipping the cables to antenna rail  312  may reduce the likelihood of a cable becoming disconnected and/or wearing prematurely when antenna platform  130  is subjected to locomotive operational conditions, such as vibration. In one embodiment each cable may be a coaxial cable with a fifty ohm characteristic impedance. 
     Antenna rail  312  may include a flange, such as flange  312   a . Flange  312   a  may include an unpainted surface that may directly contact an unpainted surface of mounting plate  134  when antenna platform  130  is assembled. Increasing the surface area of flange  312   a  may reduce the impedance between mounting plate  134  and antenna rail  312  which may increase the integrity of ground at RF frequencies. As non-limiting examples, antenna rail  312  may be screwed, soldered, or attached by another suitable fastener when antenna platform  130  is assembled. 
       FIG. 5  shows an example embodiment of a front side of antenna interface  360 . Antenna interface  360  provides the transmission path for signals between antenna platform  130  and locomotive  100 . Specifically, antenna interface  360  provides the transmission path for signals between the antennas of antenna platform  130  and the antenna interface bulkhead on roof  122  of locomotive  100 . In one embodiment, antenna interface  360  includes an interface mounting plate  510  and one or more extenders  520  (e.g., extenders  520   a ,  520   b ) attached to and extending through interface mounting plate  510 . Interface mounting plate  510  may be attached to mounting plate  134 . In an alternate embodiment, interface mounting plate  510  may be integral with mounting plate  134 . Interface mounting plate  510  may include a conducting material. The number of extenders  520  may be greater than or equal to the number of antennas of antenna platform  130 . A first end of each extender  520  includes a connector for connecting to a cable from an antenna. Thus, extenders  520  may be connected to cables  350  and  352 . In one embodiment, each extender  520  includes a first end with an SMA connector. In one embodiment, each extender  520  has a characteristic impedance of fifty ohms. As should be appreciated, the one or more extenders  520  provide respective discreet electrical pathways through the mounting plate  510  for the cables  350  and  352 . The antenna interface  360  may include plural extenders  520   a ,  520   b  as shown in the drawings, or the antenna interface  360  may include a single, integrated extender unit that has plural connectors for connecting the cables  350  and  352 . 
     Each extender  520  includes a second end on the opposite of interface mounting plate  510  as illustrated in  FIG. 6 , which shows an example embodiment of antenna interface bulkhead  610  and mounting hardware for connecting antenna platform  130  to roof  122  of locomotive  100  and antenna interface bulkhead  610 . The second end of each extender  520  may include a blind mate connector  521  for connecting to antenna interface bulkhead  610 . Antenna interface bulkhead  610  provides a transmission path for signals to propagate between the antennas of antenna platform  130  and radios of locomotive  100 . Antenna interface bulkhead  610  may include a roof mounting plate  612 , a bulkhead plate  614 , and one or more blind mate connectors  620  (e.g., connectors  620   a ,  620   b ). 
     Roof mounting plate  612  may be attached to roof  122  in such a manner that a periphery of roof mounting plate  612  extends around a periphery of a hole in roof  122 . (See  FIG. 7  for a cross-section view that shows the roof hole and other holes referred to herein.) Roof mounting plate  612  may be welded to roof  122  or attached to roof  122  with suitable fasteners, such as screws, bolts, rivets, etc. Roof mounting plate  612  includes a hole for routing one or more cables to signal hub  160  or to radios, such as radio  140 , for example. The hole in roof mounting plate  612  may be covered by bulkhead plate  614  when bulkhead plate  614  is attached to roof mounting plate  612 . In an alternate embodiment, bulkhead plate  614  may be integral with roof mounting plate  612 . Roof mounting plate  612  and bulkhead plate  614  may include a conductive material. Thus, roof mounting plate  612  and bulkhead plate  614  may be electrically connected to the chassis of locomotive  100 . It may be desirable to remove paint on roof  122  where roof mounting plate  612  attaches to roof  122  to decrease the impedance between roof mounting plate  612  and roof  122 . The interface between roof mounting plate  612  and roof  122  may be sealed to reduce or prevent water intrusion into cab  120  from the hole in roof  122 . Sealing may include welding and/or caulking around the periphery of roof mounting plate  612 . The hole in roof  122  may be used for transmission between multiple antennas and multiple radios and so fewer holes in roof  122  may be needed than in a conventional installation with one hole per antenna. Thus, there may be fewer areas for water to intrude compared to a conventional installation with one hole per antenna. 
     Each blind mate connector  620  may be connected to bulkhead plate  614  and a cable which may be threaded through the hole in roof  122  and connected to radio  140  or signal hub  160  in cab  120  of locomotive  100 . When antenna platform  130  is attached to antenna interface bulkhead  610 , the blind mate connectors  620  connect, or mate, to the blind mate connectors  521  of extenders  520 , forming a low loss transmission path from antennas of antenna platform  130  into locomotive  100 . Blind mate connectors  620  and the blind mate connectors  521  of extender  520  have opposite genders. In one embodiment, the blind mate connectors  620  are male and the blind mate connectors  521  of extenders  520  are female. In an alternate embodiment, blind mate connectors  620  are female and the blind mate connectors  521  of extenders  520  are male. The alignment of each blind mate connector determines which antenna may be connected with each cable in cab  120 . For example, the end of extender  520   a  (forming part of and/or electrically connected to a blind mate connector  521 ) aligns with blind mate connector  620   a  when antenna platform  130  is attached to antenna interface bulkhead  610 . Thus, the antenna connected to extender  520   a  may be connected to the cable connected to blind mate connector  620   a . Similarly, extender  520   b  aligns with blind mate connector  620   b  when antenna platform  130  is attached to antenna interface bulkhead  610 . Thus, the antenna connected to extender  520   b  may be connected to the cable connected to blind mate connector  620   b . The cable connected to blind mate connector  620   b  may be a coaxial cable with a characteristic impedance of fifty ohms. The cable may vary from a few inches long to many feet long. In one embodiment, the cable may be twenty-five feet long and thus, the cable may be directly connected to radio  140  or signal hub  160 . In another embodiment, the cable may be eighteen inches long and thus, the cable may be connected to radio  140  or signal hub  160  by a second cable. 
     As should be appreciated, in an embodiment, the antenna interface bulkhead  610  includes one or more first blind mate connectors  620 , and the antenna platform  130  includes one or more second blind mate connectors  521 . The first blind mate connector(s)  620  and the second blind mate connector(s)  521  are aligned and configured so that when the antenna platform is attached to the antenna interface bulkhead, respective aligning first and second blind mate connectors detachably mate with one another for establishing an electrical connection between a cable connected to the first blind mate connector and a cable connected to the second blind mate connector, and thereby an electrical connection between an antenna and a radio or other electronic device in the locomotive. 
     The arrangement of blind mate connectors  620  of the antenna platform  130  may form a pattern. Similarly, the arrangement of blind mate connectors  521  of extenders  520  may form a corresponding pattern. In one embodiment, the arrangement of blind mate connectors  620  and  521  may each form a hexagonal pattern. Other non-limiting examples of patterns may include square, circular, rectangular, or other suitable patterns. The alignment of blind mate connectors  620  to blind mate connectors  521  determines which antenna may be connected with each cable in cab  120 . Thus, it may be desirable to attach antenna platform  130  in a known orientation so that it is known which antenna is connected with each cable in cab  120 . Antenna interface  360  and antenna interface bulkhead  610  may be mechanically keyed so that antenna interface  360  may fit onto antenna interface bulkhead  610  in a single orientation only. In other words, antenna interface bulkhead  610  may be configured to attach to antenna interface  360  of antenna platform  130  in one orientation. In one embodiment, a hole  616  of mounting plate  134  may be configured to fit onto bulkhead plate  614  in a single orientation. For example, hole  616  of antenna platform  130  may be shaped to receive bulkhead plate  614 . In one embodiment, bulkhead plate  614  may include a chamfer on one corner and hole  616  may extend around the chamfer so that hole  616  may fit onto bulkhead plate  614  in a single orientation. Antenna interface  360  may include one or more pins, which may fit into one or more holes of antenna interface bulkhead  610  when antenna platform  130  is in a desired orientation. For example, antenna interface  360  may include one or more pins arranged in an asymmetric pattern, which align with one or more holes of antenna interface bulkhead  610  when antenna platform  130  is in a desired orientation. When the pins and the holes are misaligned, antenna platform  130  cannot be attached to locomotive  100  because the pins will not slide into the holes. When the pins and holes are aligned, antenna platform  130  may be attached to locomotive  100  because the pins will slide into the holes. 
     In one embodiment, antenna interface  360  may include a pin  630   a  for inserting into a hole  632   a  of antenna interface bulkhead  610  in one orientation (of the antenna interface  360  with respect to the antenna interface bulkhead  610 ) only. In another embodiment, antenna interface  360  may include a plurality of pins for inserting into a plurality of holes of antenna interface bulkhead  610  in one orientation only. For example, antenna interface  360  may include four pins, such as  630   a - 630   d , for inserting into four holes, such as  632   a - 632   d , respectively, of antenna interface bulkhead  610  in one orientation only. Thus, antenna interface  360  may fit onto antenna interface bulkhead  610  when pin  630   a  aligns with hole  632   a , pin  630   b  aligns with hole  632   b , pin  630   c  aligns with hole  632   c , and pin  630   d  aligns with hole  632   d . It may be desirable for the plurality of holes and the plurality of pins to extend around a periphery of the blind mate connectors to reduce the potential risk of the plurality of pins damaging the blind mate connectors if antenna platform  130  is misaligned. In an alternate embodiment, antenna interface  360  may include one or more holes keyed to one or more pins of antenna interface bulkhead  610  so that antenna platform  130  may be attached to antenna interface bulkhead  610  in one orientation. 
     A RF gasket  640  may be inserted between antenna platform  130  and antenna interface bulkhead  610  to reduce or prevent water intrusion and to electrically connect antenna platform  130  and antenna interface bulkhead  610 . In one embodiment, RF gasket  640  may include a hole generally in the shape of bulkhead plate  614  and holes to pass fasteners between mounting plate  134  and antenna interface bulkhead  610 . In an alternative embodiment, RF gasket  640  may extend around a periphery of antenna interface bulkhead  610 . Non-limiting examples of RF gasket  640  may include conductive elastomers or conductive foam. 
     One or more brackets, such as brackets  650  and  660 , may be attached to roof  122  for attaching antenna platform  130  to locomotive  100 . In one embodiment, bracket  650  may include conductive material so bracket  650  may be electrically connected to the chassis of locomotive  100 . It may be desirable to remove paint on roof  122  where bracket  650  attaches to roof  122  to decrease the impedance between bracket  650  and roof  122 . In one embodiment, brackets  650  and  660  may be welded to roof  122 , but other suitable fasteners may be used. Bracket  650  may guide an edge of antenna platform  130  into position for attaching antenna platform  130  to locomotive  100 . Thus, bracket  650  may have a shape that conforms to one or more edges of antenna platform  130 . In one embodiment, bracket  650  may be linear for aligning with one edge of antenna platform  130 . In an alternate embodiment, bracket  650  may be L-shaped to align with two edges of antenna platform  130 . Bracket  650  may include a threaded hole for receiving a fastener, such as a screw or a bolt. If more than one bracket is provided, the brackets may be the same or similar to bracket  650  described above, and similarly connected to roof  122 . 
     Brackets and mechanical keying may enable antenna platform  130  to be quickly aligned in the correct orientation to be attached to locomotive  100 . Once in the correct orientation, antenna platform  130  may be attached to antenna interface bulkhead  610  and brackets  650  and  660  with fasteners, such as screws or bolts. For example, holes  210   a - f  may be aligned with threaded holes  670   a - f , respectively, and bolts may be driven into threaded holes  670   a - f  to attach antenna platform  130  to locomotive  100 . In this manner, antenna platform  130  may be attached to locomotive  100  and the antennas of antenna platform  130  may be connected by a low loss transmission path to radios in cab  120 , a low impedance path to ground may be formed from antenna rails  310  and  312  to the chassis of locomotive  100 , and a water resistant seal may be formed between antenna platform  130  and the hole in roof  122 . 
     Similarly, antenna platform  130  may be quickly removed from locomotive  100  by removing the fasteners holding antenna platform  130  to locomotive  100 . For example, it may be desirable to remove a first antenna platform and replace it with a second antenna platform, such as to upgrade the antennas or to replace a faulty antenna. Antenna interface bulkhead  610  may resist water intrusion and so locomotive  100  may operate without an antenna platform attached. 
       FIG. 7  shows a schematic cross-section of one embodiment of antenna platform  130  attached to locomotive  100 . Mechanical keying enables antenna interface  360  to align with antenna interface bulkhead  610  in only one orientation when antenna platform  130  is attached to roof  122 . Thus, the blind mate connectors  521  of extenders  520  of antenna interface  360  are aligned with blind mate connectors  620  of antenna interface bulkhead  610 . In this manner, an antenna mounted on antenna platform  130  may be connected by a transmission path through a hole in roof  122  to an appropriate radio in cab  120  of locomotive  100 . For example, VHF antenna  320  may be connected to a VHF radio  720 , cell antenna  330  may be connected to a cell radio  730 , 802.11 antenna  340  may be connected to a 802.11 radio  740 , 802.11 antenna  342  may be connected to a 802.11 radio  742 , cell antenna  332  may be connected to a cell radio  732 , and GPS antenna  322  may be connected to a GPS receiver  722 . 
     A low impedance RF ground plane may be formed by the mechanical assembly of antenna platform  130  and attachment to locomotive  100 . Specifically, antenna rails  310  and  312  may be grounded to roof  122  through the mechanical assembly of plates, brackets, and/or gaskets. For example, an electrically conductive antenna rail  310  may include one or more flanges in face sharing contact with electrically conductive mounting plate  134 . Mounting plate  134  may be in face sharing contact with electrically conductive bracket  650  which is in face sharing contact with electrically conductive roof  122  at chassis ground potential. Similarly, antenna rail  312  may be in face sharing contact with mounting plate  134  which is in face sharing contact with roof  122  at chassis ground potential. A combination of electrically conductive plates and an electrically conductive RF gasket may ground interface mounting plate  510  and bulkhead plate  614 . For example, interface mounting plate  510  may be in face sharing contact with mounting plate  134  which is in face sharing contact with RF gasket  640  which is in face sharing contact with roof mounting plate  612  which is in face sharing contact with roof  122  at chassis ground potential. Similarly, bulkhead plate  614  may be in face sharing contact with RF gasket  640  and roof mounting plate  612  which is in face sharing contact with roof  122  at chassis ground potential. Thus, impedance of the ground plane of antenna platform  130  may be reduced through multiple pathways to ground and surface area contact to ground that may be greater than a surface area provided by a conventional ground strap. 
     Certain embodiments of antenna platform  130  may include different configurations of antennas for communicating in different protocols. In one embodiment, antenna platform  130  may include two antennas for communicating via 802.11, and two antennas for communicating via a cellular network. Specifically, antenna platform  130  may include a ground plane and a first 802.11 antenna mounted to the ground plane with a first NMO connector. A second 802.11 antenna may be mounted to the ground plane with a second NMO connector and the second 802.11 antenna may be spaced between five and eighteen inches from the first 802.11 antenna. A first cell antenna may be mounted to the ground plane with a third NMO connector. A second cell antenna may be mounted to the ground plane with a fourth NMO connector and the second cell antenna may be spaced between fifteen and twenty-four inches from the first cell antenna. An antenna interface may include a first blind mate connector connected to the first 802.11 antenna by a first coaxial cable between the first NMO connector and the first blind mate connector. A second blind mate connector may be connected to the second 802.11 antenna by a second coaxial cable between the second NMO connector and the second blind mate connector. A third blind mate connector may be connected to the first cell antenna by a third coaxial cable between the third NMO connector and the third blind mate connector. A fourth blind mate connector may be connected to the second cell antenna by a fourth coaxial cable between the fourth NMO connector and the fourth blind mate connector. The antenna interface may include a plurality of pins (e.g., four pins) arranged in an asymmetric pattern around a periphery of the first, second, third, and fourth blind mate connectors to align with a corresponding plurality of holes (e.g., four holes) of an antenna interface bulkhead. 
     In another embodiment, antenna platform  130  may include two antennas for communicating via 802.11, and two antennas for communicating via a cellular network, one antenna for receiving a GPS signal, and one antenna for communicating via VHF. Specifically, antenna platform  130  may include a ground plane and a first 802.11 antenna mounted to the ground plane with a first NMO connector. A second 802.11 antenna may be mounted to the ground plane with a second NMO connector and the second 802.11 antenna may be spaced between five and eighteen inches from the first 802.11 antenna. A first cell antenna may be mounted to the ground plane with a third NMO connector. A second cell antenna may be mounted to the ground plane with a fourth NMO connector and the second cell antenna may be spaced between fifteen and twenty-four inches from the first cell antenna. A GPS antenna may be mounted to the ground plane with a fifth NMO connector. A VHF antenna may be mounted to the ground plane with a sixth NMO connector spaced greater than fifteen inches from the GPS antenna. An antenna interface may include a first blind mate connector connected to the first 802.11 antenna by a first coaxial cable between the first NMO connector and the first blind mate connector. A second blind mate connector may be connected to the second 802.11 antenna by a second coaxial cable between the second NMO connector and the second blind mate connector. A third blind mate connector may be connected to the first cell antenna by a third coaxial cable between the third NMO connector and the third blind mate connector. A fourth blind mate connector may be connected to the second cell antenna by a fourth coaxial cable between the fourth NMO connector and the fourth blind mate connector. A fifth blind mate connector may be connected to the GPS antenna by a fifth coaxial cable between the fifth NMO connector and the fifth blind mate connector. A sixth blind mate connector may be connected to the VHF antenna by a sixth coaxial cable between the sixth NMO connector and the sixth blind mate connector. The antenna interface may include a plurality of pins (e.g., four pins) arranged in an asymmetric pattern around a periphery of the first, second, third, fourth, fifth, and sixth blind mate connectors to align with a corresponding plurality of holes (e.g., four holes) of an antenna interface bulkhead. The first blind mate connector, the second blind mate connector, the third blind mate connector, the fourth blind mate connector, the fifth blind mate connector, and the sixth blind mate connector may be arranged in a hexagonal pattern. 
     In an embodiment, the blind mate connectors  620  and  521  are detachably mated to one another via a press fit, that is, one connector axially slides into and engages another without the need to screw or rotate the connectors. 
     In an embodiment, the antenna interface bulkhead (connected to the roof of the cab of the locomotive) is a semi-permanent, stand alone installation. Here, the antenna interface bulkhead is separately attached to the cab roof, and does not require the presence of the antenna platform or underlying cables (e.g., cables connecting blind mate connectors  620  to radios  720 ,  722 ,  730 ,  732 ,  740 ,  742 ) to remain securely in place. Thus, when the antenna platform is removed, and/or when underlying cables are removed, the antenna interface bulkhead does not come loose, and there is no substantial effect on the positioning of the antenna interface bulkhead. 
     Another embodiment relates to a radio communication system for a locomotive or other rail vehicle having a roof or other external surface. The system comprises an antenna platform and an antenna interface bulkhead. The antenna platform comprises a mounting plate, a plurality of antenna mounts connected to the mounting plate and to a ground plane, a plurality of first blind mate connectors respectively connected to the antenna mounts, and a plurality of antennas respectively connected to the plurality of antenna mounts. The plurality of antennas include at least one first antenna configured for wireless communications in a first bandwidth and at least one second antenna configured for wireless communications in a second, non-overlapping bandwidth. That is, the first bandwidth does not overlap the second bandwidth. The antenna interface bulkhead is connected to the roof or other external surface of the locomotive or other rail vehicle. The antenna interface bulkhead includes a plurality of second blind mate connectors configured to respectively mate with the plurality of first blind mate connectors of the antenna platform when the antenna platform is attached to the antenna interface bulkhead. The antenna interface bulkhead and antenna platform are configured to attach to one another in only one orientation. In another embodiment, the system further comprises a plurality of discreet electrical pathways (e.g., coaxial cables) that respectively interconnect the second blind mate connectors to electronic equipment in the locomotive or other rail vehicle. 
     When a distance or quantity is characterized herein as being “between” a first boundary and a second boundary, this means between and including the first and second boundaries, unless otherwise specified through the provision of language excluding the first and second boundaries. For example, when it is specified that a first distance may be between X inches and Y inches, where X&lt;Y for example, this means: Y≧first distance≧X. 
     It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. While the dimensions and types of materials described herein are intended to illustrate the parameters of the invention, they are by no means limiting and are exemplary embodiments, unless otherwise specified. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. Therefore, the scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, any instances of the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” “third,” “fourth,” “fifth,” “sixth,” “front,” “back,” etc. are used merely as labels, and are not intended to impose numerical or positional requirements on their objects. As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of said elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising,” “including,” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., do not denote any order or importance, but rather the terms first, second, etc., are used to distinguish one element from another.